Biomech- Lecture & LAB
Calculating pressure (AKA stress)
Force divided by surface area Weight - effect of mass and gravity Pressure - weight with the added component of surface area (pressure and stress are considered the SAME THING) Person lying down has less pressure on their body than a ballerina on their tip toes ***Pressure and stress are synonymous force/ surface area Weight/surface area
Osteokinematics vs. Arthrokinematics
Osteokinematics refers to the movements possible at that joint using anatomic planes of motion and standard terminology like adduction, abduction, flexion, extension, etc. Arthrokinematics refers to the specific movements occurring within the joint based on it's structure, like rolling, sliding, spinning and translation, etc. Arthrokinematics= More of what is happening in the JOINT- rolling, sliding spinning (ARTHROkinematics- JOINT) - terms flexion/extension is NOT RIGHT HERE
Concave/Convex rule Very important for passive range of motion (PROM) or Joint mobilizations High horse moment (no pun intended): O.T.s are able to do joint mobilizations grade 1-4, and need to showcase this!
Rumor has it that O.T. students don't learn about joint mobilizations in school and that we're not competent or capable of doing it Joint mobilizations ARE in our scope of practice! Rumor that PTs say we can't do joint mobilization but we CAN!
Concave/Convex rule Concave on convex:
When the CONCAVE joint surface is moving and the CONVEX surface is stable, rolling and sliding (arthrokinematics) occur in the SAME (or SIMILAR) direction as the body segment (osteokinematic direction) Think about the proximal interphalangeal joint (PIP) of a finger When you bend the finger (flexion: upward in anatomic position) The middle phalanx (biconcave) moves upward (or volar) as well
T/F Each tissue has different yield point depending on its make-up
(TRUE)
Axis of rotation associated with frontal plane?
(anterior/posterior axis (on front and back of body) (ex. ventral center of humeral head)
Axis of rotation associated with sagittal plane??
(medial/lateral axis)- (ex. During elbow flexion axis of rotation= medial and lateral epicondyles)
BELIEFS & DEFINITIONS • OT practice evolves from a belief that purposeful activity (occupation), including its interpersonal and environmental components, can serve to improve one's functional ability or prevent dysfunction by promoting maximal functional adaptation. • Examples of Purposeful repetitive activity for shoulder external rotation= grocery shopping, pitching in baseball or playing ping pong *The primary concern for movement involves???
*The primary concern for movement involves movement within the context of activity!!!!! Take info we have about biomechanics and apply it to what we "DO" - Example= grabbing groceries in the store - We look at the WHOLE person- look at environment and purposeful activities in addition to biomechanics
How many degrees of freedom does the radiocarpal joint have?
- 2 - Radial/ulnar deviation (adduction/abduction or medial/lateral flexion) - Flexion/extension
How many degrees of freedom does the glenohumeral joint have?
- 3 but some say 6 b/c of rotational portion of it -- sagittal, frontal, and transverse
Focus on Kinematics and Kinetics in addition to functional anatomy- Kinesiology vs. Kinematics vs. Kinetics
- Kinesiology (functional anatomy) - Kinematics (motion characteristics)- more dynamic and complex - position, velocity, acceleration - Kinetics (cause of the motion) - torque (angular), force (linear)
• The patient has increased arm flexion but is not happy because she is unable to reach the lower shelf in the kitchen. • But how much better is this than it was before?, how does this compare to how others do in the same situation or to "normal" shoulder motion? Is this what I tell the insurance company and the MD?
- Like before, pair Pair ROM with functioning is NEEDED - This part goes more into an analysis - goes into more subjective - Person unable to reach lower shelf in kitchen When we put these together, (ex. "patient requires further intervention to address all components of activity") (Assessment part of SOAP note)
Mass vs. weight
- Mass= amount of matter - Weight= involves GRAVITY acting on mass
What is the axis of rotation for elbow flexion??
- Medial and lateral epicondyles
Functional movement patterns in the clinic- less specific --Ways to describe motion that implies full motion or not (ex. Pt able to make 50% of a full fist)
- Observational measurements= less formal but considered still valid
How many degrees of freedom does the radio-ulnar joint allow?
- Pivot joint- 1 df - Radius is the one that rotates during pronation/supination- just spinning
ANATOMICAL TERMS OF POSITION Superior (cranial/cephalic) Inferior (caudal)
- Superior (cranial/cephalic): nearer to the head - Inferior (caudal): nearer to the feet
Concave ON convex
- The concave surface or joint segment is the one moving! - The convex is the one that is staying relatively stable or fixed - (ex. Tibiofemoral - concave tibia and convex femoral- in knee extension during kicking- the arthrokinematics are rolling and sliding/gliding)- little bit of a slide to catch up and a roll are going in the SAME or SIMILAR direction as the osteokinematics - (Ex. PIP joint- open chain movement (distal segment is moving) - if want to help achieve a good fist, have to help them loosen the joint first)
What is a synovial plica? - floating, folded or frayed pieces of tissue composed of the innermost layers of a joint capsule - bone spurs - heterotropic ossification - blood vessels in the joint
- floating, folded or frayed pieces of tissue composed of the innermost layers of a joint capsule
Which of the following types of joints allow the LEAST amount of motion? - synarthrosis - diarthrosis - condyloid - amphiarthrosis
- synarthrosis
Arthrokinematics= More of what is happening in the JOINT- rolling, sliding spinning (ARTHROkinematics- JOINT) - terms flexion/extension are??
- terms flexion/extension is NOT RIGHT HERE, that is osteokinematics! (be mindful on this for the final and midterm)
An example of an ellipsoid joint is --radiocarpal joint --thumb CMC joint --humeral-radial joint --humeral-ulnar joint
--radiocarpal joint
Ulnar deviation also can be considered??? - ADDUCTION - AND ALSO CONSIDERED-
AND ALSO CONSIDERED- MEDIAL flexion (b/c ulna goes TOWARD the wrist)
ANATOMICAL TERMS OF POSITION Posterior (dorsal): Anterior (ventral):
Anterior (ventral): nearer to the front Posterior (dorsal): nearer to the back
Arthro- Arthrology: Arthroscopy? Arthrodesis? Arthropometrics?
Arthro- A commonly used medical term meaning joint Arthrology: the study of classification, structure and function of joints Arthroscopy- putting a camera in a joint - a procedure for diagnosing and treating joint problems using an arthroscope Arthrodesis- fusion of the joint Arthropometrics- a measurement of the joint basically- can be really specific to the width of the joint or more like your goniometric measurement
What is the study of mechanical laws and its application to living organisms??
BIOMECHANICS (ex. Wearing high heels and adjusting your walking pattern on a slippery surface- BIOMECHANICS perspective- OR how your elbow works when you have a weight in it) • Many types of forces exist in our environment the largest force of which is gravity pulling us down. * The reaction of the body to gravitational force is a major part of this course
COG of most people= WHERE??
COG of most people= is anterior to second sacral vertebrae (near bellybutton
ANATOMICAL TERMS OF POSITION Central Peripheral
Central: nearer or toward the center Peripheral: farther or away from the center
Review of Bony Anatomy - cortical vs. cancellous bone
Cortical or compact bone exists in the outer cortex of long bones along the shaft. It is like a hard protective shell. - Cortical- More compacted- less likely to damage Cancellous bone exists at the head and neck of long bones, and is much more susceptible to injury. - Cancellous- softer, more like wispy like waffled has more space in it- easier to damage since not as compact- space allows blood flow which is necessary for health of skeleton Matters usually for fracture risk And what is required to move your body
ANATOMICAL TERMS OF POSITION External (outer) Internal (inner)
External (outer): toward or on the exterior Internal (inner): toward or in the interior
MECHANISTIC PHILOSOPHY- Focuses on??
Focuses on how a body MOVES • Viewing performance as machine-like. Breaking performance into components (explaining phenomena in purely physical or deterministic terms) • Example: activity analysis • Traditional occupational therapy is based on mechanistic philosophy. • It assumes that all patients will respond to an injury, surgery or treatment in the same way. It also assumes that measurements such as joint range of motion (ROM), and muscle strength will predict function
ANATOMICAL PLANES
Frontal plane= splits you into front and back Sagittal plane= divides into L & R b/c ends in an "L" Transverse plane= top and bottom
ANATOMICAL TERMS OF POSITION - Intermediate
Intermediate: between two structures
ANATOMICAL TERMS OF POSITION - Ipsilateral - Contralateral
Ipsilateral: on the same side of the body Contralateral: on the opposite side of the body
Types of movement analysis that is more dynamic and complex - involves position, velocity, acceleration- (motion characteristics)??
Kinematics
• The study of MOVEMENT and the active and passive STRUCTURES involved- is the definition of what??
Kinesiology! The study of MOVEMENT and the active and passive STRUCTURES involved (from the perspective of musculoskeletal anatomy and neuromuscular physiology). • Example: Measuring joint motion • For knee flexion, the active structures include the hamstrings and passive structures include the joint surfaces).
Types of movement analysis that is- (cause of the motion) - torque (angular), force (linear)
Kinetics
farther from midline- why is this important?
Lateral: farther from midline - Farther is a DISTANCE - Further is conceptual (ex. Furthering the study of kinesiology) - ***WILL DOC POINTS FOR THIS!!!
ANATOMICAL TERMS OF POSITION Lateral Medial
Medial: nearer midline Lateral: farther from midline Lateral: farther from midline - Farther is a DISTANCE - Further is conceptual (ex. Furthering the study of kinesiology) - ***WILL DOC POINTS FOR THIS!!!
Torque= more rotational- movement in the body is more associated WITH??
Movement in the body is more associated with TORQUE!!!
• In order to understand physics to apply to the body, we need to look at Newton's laws! -- which three do we need to know??
Newton's Laws 1. Inertia- a body in motion stays in motion or a body at rest will stay at rest unless otherwise interrupted by an outside force 2. F=ma- GRAVITY = V. IMPORTANT FOR THIS LAW!!! - Mass= amount of matter - Weight= involves GRAVITY acting on mass 3. Every action has an equal and opposite reaction (will be looking at ground reaction forces- (ex. Standing on ground vs. trampoline)- just like the makeup of tissue in the body also matters - Different elasticity and different densities
where to put goniometer if measuring shoulder ab/adduction??
On ventral surface Right in center of humeral head - Axis of rotation= the point where motion of the rotating body is ZERO - the pivot point for angular motion of the body or its parts - For most movements of the limbs or trunk, axis of rotation is located w/n or very NEAR the structure of the join
A BLANK joint is formed by a central pin surrounded by a large cylinder - pivot - plane - ellipsoid - hinge
PIVOT
ANATOMICAL TERMS OF POSITION Parietal vs. Visceral
Parietal: toward the external wall of the body Visceral: toward the internal organs
ANATOMICAL TERMS OF POSITION - Proximal -Distal
Proximal: nearer to the trunk (in a limb) Distal: farther from the trunk (in a limb)
Skidding tire- what example of an arthrokinematic motion?
Slide
ANATOMICAL TERMS OF POSITION - Superficial - Deep
Superficial: nearer to the surface Deep: farther from the surface
BLANK reduces the friction between joint surfaces and provides nourishment to the articular cartilage - synovial fluid - articular disc - plicae - articular ligaments
Synovial fluid
BOY, ARE THESE DIFFERENT PHILOSOPHIES! To me, this is like saying... • The patient has increased arm flexion by 40 degrees to a total of 120 degrees. ---How do you know if that's good enough?
This documentation is clear in an objective part of the note (ex. Number, number, increased since last time- BASIC) - biomech - But need to pair this with a FUNCTIONAL QUESTIONNAIRE - 0 = perfectly capable - Or 5= unable to do the task - Pair ROM with functioning is NEEDED
Pressure vs. Weight
To put very simply, pressure includes the component of surface area (SA) The same weight can be exerted on a small area or a large area, and that changes the amount of pressure. Weight - effect of mass and gravity Pressure - weight with the added component of surface area (pressure and stress are considered the SAME THING) Person lying down has less pressure on their body than a ballerina on their tip toes ---Pressure and stress are synonymous force/ surface area Weight/surface area
A saddle joint has a concave ON convex movement AND a convex on concave movement True/False
True
Cortical bone is dense and strong typically lining the outermost portion of a bone - True/False
True
Saddle joints, condyloid joints, and ellipsoid joints all permit motion in at least two planes True False
True
The three sets of cardinal planes are mutually at right angles: • Two vertical planes and one horizontal
Two vertical planes= (coronal and sagittal planes) • One horizontal plane= (transverse plane) • What distinguishes them from many other planes?? • - is that they pass through the center of gravity of the body (S2)
ANATOMICAL TERMS OF POSITION Ventral (Palmar/plantar) surface Dorsal surface
Ventral (Palmar/plantar) surface - anterior surface of the hand or inferior surface of the foot, towards the belly Dorsal surface: posterior surface of the hand or superior surface of the foot, towards the back
***What is missing in this MECHANISTIC PHILOSOPHY approach?
What is missing: - Motivation - Pain - Age - Assistance at home - Social support to ask for help if need it - Environmental set-up - Mental health (motivation, happiness, their perspective on injuries) - Joint ROM does NOT mean a person will function better than a person with less ROM - Function may vary due to fear, anxiety, and pain - These mechanistic measurements depend on INSURANCE REIMBURSEMENT- need this to show evidence to prove progress
Adding a weight to your backpack adds pressure to your feet. Is that true?
YES- This is true! Can use mass in this example if you are right or wrong (force/ surface area)
Axis of rotation
center of movement (ex. where to put goniometer if measuring shoulder ab/adduction?? On ventral surface Right in center of humeral head) - Axis= the point where motion of the rotating body is ZERO - the pivot point for angular motion of the body or its parts - For most movements of the limbs or trunk, axis of rotation is located w/n or very NEAR the structure of the join
A BLANK is an articulation that allows moderate to extensive motion
diarthrosis
IMPORTANCE OF ORIGIN AND INSERTION • Concepts will come up more later: line of pull
direction of force exerted by a muscle, depending on the orientation of its fibers, its skeletal attachments, the disposition of its tendons, and the axis of movement of any joints affected.
MECHANISTIC PHILOSOPHY If two people have the same leg length, ROM and leg strength measured with a force gauge (a gadget that measures force), it does not mean that WHAT??
it does not mean that they run at the same speed. • Speed may vary due to: • Motivation • Training and level of skill • Muscle fiber type • Similarly, two patients may have the same measurements, but their function may not be the same. Function may vary due to factors such as: • fear, anxiety, and pain
MECHANISTIC PHILOSOPHY measurements depend on INSURANCE REIMBURSEMENT--why is this??
need this to show evidence to prove progress
IMPORTANCE OF ORIGIN AND INSERTION • Concepts will come up more later: Mechanical advantage
ratio of the internal moment arm to the external moment arm. (IMA/EMA)
Example of a ball and socket joint?
shoulder (GH) joint hip joint
BIOMECHANICS - Mechanics definition
the study of motion and the effect of forces on an object - - Study of motion & effect of forces * The reaction of the body to gravitational force is a major part of this course
What distinguishes the three cardinal planes from many other planes??
they pass through the center of gravity of the body (S2)!!!
CARDINAL planes of motion-thought of as dividing EXACTLY
thought of as dividing EXACTLY (like midsagittal) - Then all 3 cardinal planes intersect at the center of gravity - There ARE non-cardinal planes (sagittal plane that is off-centered) COG of most people= is anterior to second sacral vertebrae (near bellybutton
LIMITATIONS OF BIOMECHANICAL F.O.R.
• Biomechanics does not address the cognitive, emotional, and social aspects of human occupation. • Biomechanics emphasizes the mechanics of the musculoskeletal system. • Does not balance performance components of individual function within the lived environment. • It is more beneficial to perform purposeful exercise than rote exercise.
ANATOMICAL TERMS OF MOVEMENT Circumduction
• Circumduction: circular movement combining flexion, extension, abduction and adduction Can use one word to describe all this - Or joints that move through a whole rotation - Not the elbow b/c only have flexion/extension - Wrist, shoulder and hip can do this for - Doesn't matter the direction of motion when use this Most circumduction ranges are cone-shaped movement
NON-CARDINAL PLANES
• Do not pass through the center of gravity!!! • Still dissect the body or a body segment • Still called coronal, sagittal and horizontal planes • Examples: • Dissection of an arm or a joint • Dissection of a brain • (ex. Dissection of brain= still considered sagittal just not at mid-line)
ANATOMICAL TERMS OF MOVEMENT - dorsiflexion vs. plantar flexion
• Dorsiflexion: flexing the foot at the ankle towards the anterior lower leg • Plantar flexion: foot extension at the ankle, towards the posterior lower leg
BENEFITS OF BIOMECHANICAL F.O.R.
• Easy to measure and identify deficits and change • i.e. ROM, muscle strength. • Easy to compare to standards, normative data, previous measures • i.e. What should normal shoulder flexion be? • Step-by-step procedures, treatment protocols. Useful guidelines for therapists unfamiliar with particular disorders, recovery timelines, etc. ----Many "recipes" exist on how to "treat" a particular disorder. You can find them in books, journal articles and on WebMD (or other sites). These are very helpful as a guideline for evaluation and treatment
ANATOMICAL TERMS OF MOVEMENT - eversion vs. inversion
• Eversion: moving the sole of the foot away from midline • Eversion (first position) • Inversion: moving the sole of the foot toward midline - Inversion (pigeon-toed)
SAGITTAL (MEDIAN) PLANE Joint motions occurring in this plane
• Flexion: two body segments moving toward each other (ex. Flexing elbow to shoulder) • Extension: two body segments moving away from each other (ex. Extending the knee away from thigh) • Hyperextension is extension BEYOND the anatomic reference position (sometimes still referred to as extension)
ANATOMICAL TERMS OF MOVEMENT - flexion vs. extension
• Flexion: two body segments moving toward each other; Bending or decreasing the angle between body parts • Extension: two body segments moving away from each other; Straightening or increasing the angle between body parts Ulnar deviation also can be considered??? - ADDUCTION - AND ALSO CONSIDERED- MEDIAL flexion (b/c ulna goes TOWARD the wrist)
BOTH MECHANISTIC AND TRANSFORMATIVE PHILOSOPHIES ASSIST THERAPISTS explain how both help
• In healthcare, we must always document change/improvement for insurance to pay for our services. • We use the mechanistic theory to document biomechanical changes, and transformative theory to document the meaning of these changes for the individual within their personal contexts.
MECHANISTIC PHILOSOPHY The benefit of the mechanistic philosophy is
• In occupational therapy it is difficult to accurately measure function. • However, it is easy to accurately complete a biomechanical assessment (measure ROM and strength). • We combine biomechanical measurements with our interviews or self-reports of function (or our evaluation of ADLs) to assess function. **good to be used as a guide to show progress Can also combine it with other forms including interview and self-report to assess function
INTEGRATION OF BIOMECHANICS WITH OTHER MODELS OF PRACTICE Kinesiology and the Rehabilitation Model
• Kinesiology provides evaluation of motion • Biomechanics also allows evaluation of motion AND the forces that are present • Mechanistic FOR in the context of solving problems associated with meaningful activities (rehabilitation model)
ANATOMICAL TERMS OF MOVEMENT • Lateral (external) rotation: • Medial (internal) rotation:
• Medial (internal) rotation: moving around the longitudinal axis, internally • Lateral (external) rotation: moving around the longitudinal axis, externally
THE BIOMECHANICAL FRAME OF REFERENCE OT models based on biomechanics provide a means to
• OT models based on biomechanics provide a means to: • Outline and define musculoskeletal problems • Develop exercises and activities that restore and maintain function • Design and fabricate adaptive equipment to meet functional activity goals • Measure functional musculoskeletal progress in treatment What is the best way to adjust this activity and WHY?? Why is it easier to do it one way vs. another - Need to understand the deep concepts to answer these challenging questions
ANATOMICAL TERMS OF MOVEMENT - opposition, retroposition, radial abduction, palmar abduction
• Opposition: moving the thumb pad towards another digit • Retro-position: moving the thumb back to its anatomical position - (Retropulsion (basically same thing as extension of the thumb) - Radial abduction= moving thumb away from index finger (90 degrees) - Palmar abduction= moving thumb away from hand and pointing it anteriorly Thumb uses different terminology - Combo of abduction, flexion, and rotation - Thumb is a totally different animal
CORONAL (FRONTAL) PLANE
• Passes from one side to the other, dividing the body into front (anterior, ventral) and back (posterior, dorsal) portions • Movement in this plane: • Abduction: away from midline • Adduction: toward midline Axis of rotation associated with frontal plane (anterior/posterior axis (on front and back of body)
SAGITTAL (MEDIAN) PLANE
• Passes the body from front to back, dividing it into right and left portions • A particular sagittal plane, the mid-sagittal or median plane lies in the midline and divides the body into equal right and left halves
HORIZONTAL (TRANSVERSE) PLANE
• Passes the body from side to side and front to back and are parallel to the horizon, dividing the body into upper (superior, cephalic) and lower (inferior, caudal) portions • Joint motions occurring in this plane are movements about the longitudinal axis, such as: • Medial (internal) rotation • Lateral (external) rotation
Iatrophysics- means??
• Physics* applied to medicine ("Iatro" = healer or medicine) • In order to understand physics to apply to the body, we need to look at Newton's laws!
ANATOMICAL TERMS OF MOVEMENT - supination vs. pronation
• Supination: rotating the forearm and hand laterally so the palm faces anteriorly • Pronation: rotating the forearm and hand medially so that the palm faces posteriorly
ANATOMICAL (CARDINAL) PLANES The three sets of cardinal planes are mutually at what angle??
• The three sets of cardinal planes are mutually at right angles: • Two vertical planes= (coronal and sagittal planes) • One horizontal plane= (transverse plane) • What distinguishes them from many other planes?? • - is that they pass through the center of gravity of the body (S2)
TRANSFORMATIVE PHILOSOPHY- definition
• The world is dynamic, constantly changing resulting in individual and systemic changes. • Strays from the mechanistic theories to address the individual IN CONTEXT!!! • WHO the person is, when/where they live, what they do, motivation, etc. all combine to influence every situation WHO IS THE PERSON? Digs into the "REALISTIC"
ANATOMICAL (CARDINAL) PLANES
• Three imaginary planes • Arranged PERPENDICULAR to each other • Pass through the body in the anatomical position (AP) • Their axes intersect at the center of gravity (COG) • The COG is a point anterior to the second sacral vertebrae (S2)
ANATOMICAL POSITION
• To avoid confusion, anatomical terms of position and movement are defined in internationally accepted convention • Anatomical position is when a person: • Stands erect with feet together • Upper limbs by the sides • Feet, face, eyes and palms of the hands directed forward Used in documentation so someone else reading note understands what was done - Universal language everyone can understand
BOTH MECHANISTIC AND TRANSFORMATIVE PHILOSOPHIES ASSIST THERAPISTS ---why Transformative philosophies
• Transformative philosophies put our patient in their own individual CONTEXT so that the information we gain through objective measurement has meaning.
• The Biomechanical FOR-
• Uses the mechanistic principles of motion and force to evaluate and treat patients and their problems. • Uses the principles of biomechanics and kinesiology to evaluate, design and modify environments or equipment.
BOTH MECHANISTIC AND TRANSFORMATIVE PHILOSOPHIES ASSIST THERAPISTS --why MECHANISTIC??
• We need kinesiology (functional anatomy) and biomechanics (mechanistic theory applied to living organisms) to • Measure status • Measure change • Understand the mechanics of motion and force treatment, for example • Muscle strengthening/conditioning • Modifying performance of daily occupations • Environmental modifications Does the person need a reacher? - Ways to intervene with the task Do we believe it is able to regain ROM or do we have to go an adaptive route?
Kinesiology
• the scientific study of the muscular activity, anatomy, physiology, and mechanics of the movement (Mosby's Dictionary). • The study of MOVEMENT and the active and passive STRUCTURES involved (from the perspective of musculoskeletal anatomy and neuromuscular physiology). • Example: Measuring joint motion • For knee flexion, the active structures include the hamstrings and passive structures include the joint surfaces). Kinesiology= FUNCTIONAL anatomy - Use concepts to measure joint ROM * In occupational therapy we use measurements of motion everyday either formally or informally.
Biomechanics definition
• the study of mechanical laws and their application to living organisms, especially the human body and its locomotor systems (Mosby's Dictionary). ***• Many types of forces exist in our environment the largest force of which is gravity pulling us down. - Example: The action of forces includes things such as contraction of the biceps to lift the weight of an object, the forearm and hand or adjusting your walking pattern on a slippery surface or when you are wearing high heels. - Study of mechanical laws and its application to living organisms (ex. Wearing high heels and adjusting your walking pattern on a slippery surface- BIOMECHANICS perspective- OR how your elbow works when you have a weight in it)
How many degrees of motion are allowed at the glenohumeral joint? 3 2 5
3
TENODESIS
Flexing of the fingers through tendon action of the extrinsic finger flexor muscles when they are stretched across the wrist joint during wrist extension. This mechanism is used for functional grip
Joint type--Hinge Primary Angular motions Mechanical analogy Anatomic examples
Flexion and extension only Door hinge Humero-ulnar Interphalangeal
What is Ergonomics (also called human factors)?
O The name ergonomics comes from the combination of two Greek words - "ergos" meaning work and "nomo" meaning natural law O Ergonomics is the scientific study of human work
Recall Newton's Laws Newton's 1st law:
OBJECTS IN MOTION TEND TO STAY IN MOTION AND OBJECTS AT REST TEND TO STAY AT REST UNLESS ACTED UPON BY AN UNBALANCED FORCE • AKA: OBJECT'S VELOCITY WILL NOT CHANGE UNLESS EXTERNAL FORCE IS APPLIED 1st= law of inertia- objects in motion stay in motion, objects at rest stay at rest unless external force applied
Factors in Stability • IMAGINE YOURSELF ON A THIN LEDGE OF ROCK, HIGH ON A FACE OF A MOUNTAIN • HOW SHOULD YOU POSITION YOURSELF? • STAND UPRIGHT / CROUCH DOWN LOW • PLACE YOUR FEET CLOSE TOGETHER / SPREAD THEM APART • LEAN FORWARD, BACKWARD, LEFTWARD, RIGHTWARD / PLANT YOURSELF DIRECTLY OVER YOUR FEET • WOULD YOU TAKE OFF YOUR BELT PACK / KEEP ITS WEIGHT AROUND YOUR WAIST???
How should you position self if looking over a cliff? - Crouch down low - Spread feet apart - Plant self directly over your feet - Keep weight around waist
According to Wolff's law, are bone spurs reversible?
Technically YES - According to Wolf's law are bone spurs reversible - Technically YES but takes too long- would have to immobilize for a long time - But we have a surgery that debrides and smooths it out
What connects muscles to bones?
Tendons- - think of this as one unit muscle and tendon- part of somatic nervous system
Ground Substance
- Ground substance= more proteins and water Glycosaminoglycans, H2O and Solutes
Active-length tension If a muscle is overstretched at is end range,
- If a muscle is overstretched at is end range, cannot generate active force Then no myosin binding to actin so no tension occurs - If muscle is really long, use tension built into muscle to change position- use passive tension built up from titin
How many degrees of freedom does the humeral-ulnar joint have?
- Humeral-ulnar joint- hinge has ONE df (flexion/extension)
Muscle tone- hyper/hypotonia
- Hypertonia is increased muscle tone or activity § With spasticity, a quick stretch causes a reflexive contraction (sometimes a jerking motion called clonus) § A low threshold elicits an action potential - Hypotonia is less than normal muscle tone or activity § In cases of flaccidity, an action potential can't be stimulated or it takes a lot to trigger it Hypertonia- increased muscle tone or activity - Some people just have more tone than others in their muscles - some have a higher resting voltage - Others have softer resting muscles based on genetics
Applying the rules of concavity and convexity to the humero-ulnar joint in open vs. closed chain
1. in an open chain, concave ulnar surface rolls and glides in same direction on convex humeral surface. 2. in a closed chain, the convex humeral surface rolls and glides in opposite directions on the concave ulnar surface.
Muscle Fiber Angle Pennation angle
: angle between the muscle fiber and the tendon - When 0 deg: all fibers parallel to the tendon ~100% of force generated by muscle is transmitted to the tendon and across the joint - When >0 deg: fibers are oblique to the tendon Only a portion of the force is transmitted through the tendon ****Note how the tendon goes through the entire muscle!
LABYRINTHINE REFLEXES - A VARIETY OF EYE, TRUNK, AND LIMB MOVEMENTS DUE TO STIMULATED HAIR CELLS IN THE LABYRINTH --what is the labyrinth??
= VESTIBULAR SYSTEM OF THE INNER EAR • GRAVITY CAUSES MOVEMENT OF SMALL CRYSTALS (= OTOLITHS) DURING HEAD MOVEMENTS STIMULATES HAIR CELLS TO TRANSMIT INFO TO BRAIN ABOUT HEAD POSITION BARRIER - STRENGTHENING MUSCLES Will go more into depth with this in the sensory lecture into detail about vestibular system - Labyrinthe= your response to gravity and changes in movement - basically what you need to know for now
Active Insufficiency
When a muscle-tendon unit crosses more than one joint, it has less strength to exert over all the joints-- cannot shorten anymore, occurs with the agonist. when a 2 joint muscle contracts (shortens) across both joints simultaneously
What is the physical problem that arises if the footplates are positioned too high? increases pressure on neck increases pressure on buttocks and sacrum increased base of support increased muscle tone
increases pressure on buttocks and sacrum
Which landmarks are particularly at risk of pressure ulcer when seated for a prolonged period of time? ischial tuberosities olecranon processes distal thigh all of the above
ischial tuberosities
- What connects bone to bone?
ligaments
Axis of rotation associated with transverse plane??
longitudinal axis - (ex. For measuring shoulder external rotation place goniometer on olecranon process (axis of rotation))
People who use sports chairs may sacrifice ______ to gain _______. stability, speed and maneuverability weight, access stability, aesthetic speed, stability
stability, speed and maneuverability
Gravity and the Human Body CENTER OF GRAVITY (COG)
• THE BALANCE POINT, • LOCATED IN OR NEAR A BODY, • WHERE THE SUMMATION OF ALL THE GRAVITATIONAL FORCES (RESULTANT FORCE) ACTING ON THE BODY'S COMPONENTS
Base of Support WHAT HAPPENS TO THE BASE OF SUPPORT DURING THE SWING PHASE WHEN ONLY THE CRUTCH TIPS ARE ON THE GROUND?
• THE BASE OF SUPPORT IS ONLY THE SMALL AREA BETWEEN THE CRUTCH TIPS. UNTIL ONE OR BOTH FEET ARE ON THE GROUND THE BASE OF SUPPORT IS SMALL.
How many degrees of freedom does the elbow have? 1 2 3
1
1. What is the difference in the tilt point with a wheelchair with and without footrests and why?
The wheelchair with footrests has a tilt point that is further back because the center of gravity is shifted forward due to it being a larger system. This is due to the further back tilt point shifting the center of gravity to still be over the base of support.
Job Analysis
Therapists often will be called on to conduct a job analysis/work site evaluation O Our background knowledge regarding the nervous system, anthropometry, kinesiology, human development, anatomy and physiology, work capability analysis, seating and posture, and workplace design allow us to give valuable input regarding this ergonomic analysis O Consult with other ergonomics professionals may be needed Use info from anatomy and kines ---Looking at every component of their environment, posture, tools using- bring it together into a thorough report
Joint type-Ball and socket Primary Angular motions Mechanical analogy Anatomic examples
Triplanar motion Spherical convex surface, concave cup Glenohumeral Coxofemoral (hip)
A joint must allow motion in at least two planes in order for it to circumduct True False
True
A muscle must receive a sufficient amount of resistance to stimulate hypertrophy True False
True
According to the force-velocity curve, as the load is increased with an eccentric contraction, rate of change in the muscles length also increases. True False
True
Eccentric activations produce greater force per unit of muscle True False
True
Neural connections in the motor cortex actually help increase muscle strength True False
True
When moving from seated to standing position, the Femur moves on the relatively fixed Tibia, so the arthrokinematics follow convex ON concave rule. True False
True
When reaching for an item on a tall shelf, the humeral head slides inferiorly on the glenoid True False
True
When reaching to extend the elbow, the concave ulna rotates around the convex distal humerus, so as the elbow extends, the ulna rolls in the same direction (posteriorly roll and posterior slide) True False
True
- Sliding filament theory:
Z lines move toward each other, sarcomere shortens
Muscles Strength and Tone Manual muscle testing (MMT):
a 6 point scale of 0-5 for testing muscle strength in a SINGLE maximal voluntary contraction (MVC) - MMT want to test in a SINGLE maximal voluntary contraction - But fatigue becomes an issue
Which is an antagonist? - a muscle or group that has the action opposite to a particular primary mover - motion caused by a stimulated muscle - muscle or group that is most directly related to the initiation of a particular movement - a muscle that works closely with another muscle to execute a movement
a muscle or group that has the action opposite to a particular primary mover
MATH!! a) Approximate location of center of gravity for each segment relative to the elbow Do the same thing you just did but use these percentages 15 cm = length of hand 25 cm= length of forearm COG is where the load will be drawn How far is COG of hand from the elbow Adding entire distance of forearm plus 7.59 cm to get moment arm if holding something in your hand Axis of rotation on elbow, load = COG of forearm In order to find out what the load is, we use M= F X D- moment is the torque exerted on the elbow joint So we need to know the force, which is the load here, the weight comes at the COG M= F X D M= 20 lbs X 10.75 cm= amount of torque exerted on the elbow More concerned with COG of hand= weight exerted on the wrist COG is where the force is which could be weight of the hand - Want to be able to calculate the torque
a) COGfa = 43% X 25 cm = 10.75 cm from elbow COGhand= 50.6% X 15cm = 7.59 cm from wrist COG hand= 7.59cm + 25 cm= 32.59 cm from elbow
Segment Weights • PERSON WEIGHS 450 N (101 LB-F), FOREARM LENGTH = 25 CM, HAND LENGTH=15 CM a) ESTIMATE THE WEIGHT OF RIGHT HAND AND FOREARM b) APPROXIMATE POSITION OF COG FOR EACH SEGMENT RELATIVE TO ELBOW a) Estimate the weight of the right hand and forearm hand= 0.6% forearm= 1.5%
a) Estimate the weight of the right hand a) Fhand= 0.6% X 450 N= 2.7 N Ffa= 1.5% X 450 N= 6.75 N
-Shoulder extended, elbow extended, forearm pronated= example of what type of insufficiency??
example of passive insufficiency -Passive insufficiency if cross more than one joint, can't stretch it over these joints as easily
- If muscle is really long, use tension built into muscle to change position- where does this come from?
use passive tension built up from titin - (ex. At end range of quad stretch, when you release, passive tension in quads releases leg when you let go)
Wolff's Law - Little box in reading off the side!
Bone is a dynamic tissue that is constantly adapting to external forces "Bone is laid down in areas of high stress and reabsorbed in areas of low stress" -Julius Wolff Explains bone spurs in osteoarthritic (OA) joints Bone density decreases in people with paralysis or other non-use conditions, increasing the risk of fractures in people with spinal cord injury (SCI) - An extra bone is laid down in area of high stress and reabsorbed when not used - So bone is not as stable as most people think - Has the potential to CHANGE - Not just here is your skeleton - This is why people with osteoarthritis get bone spurs- put down extra bone to protect skeleton - Non-use conditions get lower bone density (so increased risk of fracturing) like in people in a wheelchair - Bones rely on forces exerting around them, this is why bone density INCREASES for runners - Why they fracture less generally
Axis of rotation Medial-lateral, anterior-posterior and vertical/longitudinal are still appropriate descriptions But in truth, the axis tends to be WHAT?
But in truth, the axis tends to be a little off-kilter Lets look at the Glenohumeral joint What is the axis of rotation for circumduction? Try this through the whole range in the sagittal plane Where do you feel restricted? Why do you think that is? Skeletons can help! (demonstrate) With the axis of rotation - Good to think about our basic knowledge we have - End of the day it is not exactly perfect b/c not every joint is perfectly angle - (ex. Really hard to stay in sagittal plane with shoulder flexion) - So going to be a little bit rotated
Joint Structure Dense connective tissues:
Capsule Ligaments Tendons - Capsule- supposed to be really tight structures- and restrict movement beyond normal range but some people have more dense tight structures and other have hypermobility functional abilities - Ligaments are ALSO supposed to restrict movement beyond normal range (so if trying to prevent hyperflexion would be placed BEHIND the knee!)
Proximal on distal? (closed or opened)
Closed chain: Proximal-on-distal: Weight bearing (distal is fixed, proximal is moving)
Biologic Makeup of Joints - Joints are made of a bunch of different substances Fibrous Proteins--what two kinds are there?
Collagen and Elastin (Foreign people (CE) Collagen and elastin= fibrous proteins - collagen= tighter part, resists stretch and supports joint Type 1 collagen: thick, rugged fibers with little stretch Type 2 collagen: thinner, providing a framework for shape and consistency of structures Collagen type 2= easier to damage from outside forces Elastin: what do you think this is like? - wants to increase flexibility of tissues - (ex. Tendons have more elastin than collagen but always a combo of both in CTs and tendons)
Leverage
Describes the effect of a force based on it's distance (moment arm) from the axis of rotation Lets consider how external forces exerted near a joint affect it. Trauma example: Dog leash wrapped around thumb when she sees a squirrel before you do. Close to the joint, but high force Cumulative strain example: Riding a bicycle with prolonged pressure on the distal aspect of the first metacarpal. Farther from the joint requires less force to cause damage
Cell types in a joint- fibroblasts
Fibroblasts: stimulate collagen production, form a structural framework for tissues, important in wound healing - collagen is important to HEALING- help improve collagen formation - so fibroblasts will increase and collagen turns to articular cartilage and scar tissue - so good and bad ---BOTH chondrocytes and fibroblasts are also responsible for maintenance and repair of tissue Both responsible for maintenance and repair- pull out inflammatory cells and bring good ones in generally
Joint Supports- what structure serves to protect joints?
Muscles serve to protect the joints! We will talk about this more, but JP and his partner had a great example of how muscles activate to stabilize joints around the thumb last week! Could you tell the class how that works when popping the top of toothpaste? More to come on this in next week's lecture! Muscles around the thumb joint help stabilize it One set of muscles stabilize the joint while the others flip the cap of the toothpaste If you need to apply a force at the tip of the thumb how do you keep your thumb in the same position? - Multiple muscles stabilize thumb if you had less muscles healthy, your thumb would be less stable! - Muscles are actually supporting your joint - Just like when you reach for an object, your muscles stabilize shoulder otherwise joints would collapse
Open vs. Closed PACKED Positions
Open (loose) packed: the most wiggle room allowed Most wiggle room in the joint= open-packed Close packed: joint segments are tightly closed, closest together Least wiggle room in the joint= close-packed Closed and open packed= Used to change the congruency of joints (ex. Shoulder joint is so close together) - Each joint has some change in how it lines up with a segment sometimes its closer or farther away
Distal on proximal? (closed or opened)
Open chain: Distal-on-proximal: Non-weight bearing (proximal is fixed, distal is moving)
Open vs. Closed chain movements
Open chain: Distal-on-proximal: Non-weight bearing (proximal is fixed, distal is moving) Closed chain: Proximal-on-distal: Weight bearing (distal is fixed, proximal is moving)
Joint Structure Articular cartilage
Paired with synovial fluid, coefficient of friction is 0.05-0.02 To put that in context, ice on ice is 0.1 Avascular: relies on the subchondral bone for viability(1) - Articular cartilage= AVASCULAR!! - Even though bouncy balls moved around pretty good, synovial fluid made it even smoother and have less resistance - So very slippery in the joint!! Almost half the friction of ice in a healthy joint of course
Concave/Convex rule Convex on concave:
When the CONVEX joint surface is moving and the CONCAVE surface is stable, rolling and sliding (arthrokinematics) occur in the OPPOSITE direction as the body segment (osteokinematic direction) Think about the glenohumeral (GH) joint As you lift your arm (flexion: body segment moves upward), The humeral head rolls and slides opposite: downward
"Appropriate assessments that gather data on occupational skillfulness and effectiveness include the standardized BLANK and non-standardized observation using BLANK
"Appropriate assessments that gather data on occupational skillfulness and effectiveness include the standardized Assessment of Motor and Process Skills (AMPS) and non-standardized observation using structured analysis methods
Hinge joints
- Hinge joint surfaces are very congruent- close together and do not get as much rocking here b/c less space - More of a cylinder here not a ball
What is Ergonomics
(also called human factors)? O A field of study focusing on work performance with an emphasis on worker safety and productivity, fitting the worker to the job O A design philosophy that focuses on supplying a product (or setup/procedure) that ensures safety, ease of use, comfort, and efficiency O A field focused on prevention & wellness Basically making sure things doing at work are ergonomically correct So things that you can control are fitting with the job to decrease load on the body
Saddle joint
(ex. Thumb CMC is like saddle on a horse and a rider) Distal segment= concave on convex (palmar abduction) - So osteokinematics and arthrokinematics happen in SAME directions - Radial abduction ("R" and Rider) - As rider tips forward into flexion (rounded part) on convex on concave So osteokinematics and arthrokinematics happen in OPPOSITE directions
Agonist, Antagonist, and Synergists
- Agonist: A muscle that acts as the primary mover for a specific joint motion - Antagonist: A muscle that opposes the agonist for a specific joint motion - Synergists: Muscles acting together to produce specific movements The muscles of our body work synchronously to provide coordinated motion, maximum strength and to prevent injury Deltoid = prime mover when lifting abducting arm- latissimus dorsi wants to adduct arm (antagonist) - eccentrically contract to resist this
Stick a piece of tape on the sides of the popper to simulate joint structures Try sliding the ball around back and forth in flexion and extension - Was that kinda squeaky?? Use Vaseline to lubricate the joint surfaces and try again --this is acting like?
(this is like synovial fluid!) With the joints lubricated- does it feel easier? - YES! - As soon as you add the synovial fluid- it slides around- very low resistance
Joint Structure Fibro- cartilage
*** ALL serve as shock absorbers Labrum of the shoulder Add stability to the joint like a suction cup! (OK, you can pop your popper now, but protect your eyes!!) Articular disc of the wrist (triangular fibrocartilage complex) Meniscus of the knee Intervertebral discs - Shock absorber to various joints- meniscus - Labrum is more like your suction cup! Sucks the humeral head into it- help to keep shoulder in the joint
***Majority of splints= what type of lever?
***Majority of splints= first-class lever systems Goal when designing a lever system or splint= generate the most efficient work! Both effort and resistance arms should conform to the structures they touch and should incorporate enough surface area for adequate pressure distribution - When forces act on a joint, there must be a balance-counter-balance effect - A short, narrow, and shallow effort arm is likely to cause discomfort and pressure - a well-molded arm dissipates pressure
Center of Gravity • IN NON-UNIFORM OBJECTS, (SHAPE AND/OR MASS DISTRIBUTION) THE COG IS THE MEAN LOCATION OF ALL THE MASS IN A SYSTEM • IF OBJECT IS ACTED UPON BY AN UNBALANCED FORCE AT A POINT OTHER THAN COG, IT WILL ROTATE how??
, IT WILL ROTATE ABOUT THE COG. • ACCELERATION OF THE COG IS G AT ALL POINTS OF THE TRAJECTORY (9.81m/s2) COG generally follows a very predictable trajectory when looking just at COG - So for bat, COG is closer to where the most mass is, COG follows this certain perfect arc - Same with a wrench - lighter weight on end sort of spins around COG - When you drop something, it also has a consistent downward trend of COG despite how the other parts of object move differently
How many synovial joints in the body?
- 6 types with varying shapes - Synovial joints MOVE - Joints determine position of body
• = COM = COG COG= Center of mass (COM) in UNIFORM gravitational fields
- A lot easier to determine COM in uniform objects - Divide into 3 planes (of AP planes of motion) - Point where these three planes intersect - COG= COM - It's not necessarily clear where COG is - Will ID a couple ways to find it when its unknown
Difference Between Scalars and Vectors Example: Force required to move an object
- A scalar quantity would define a load (magnitude) as requiring 75 pounds to move it - A vector quantity would clarify whether the force was to lift (vertical), or slide the load (horizontal)
Total length tension curve for a typical muscle: - At shortened lengths all force if generated passively or actively??
- ACTIVELY
Varus and Valgus stress
- Also there is stress from external forces you can get on a certain side of the joint - (ex. Lateral epicondylitis) - When testing ligaments- can apply pressure in direction you think that ligament may be damage to check if joint is too loose - If damaged its going to be way easier to move than the non-affected side varus= rupture of LCL, valgus= rupture of MCL
- Articular cartilage is vascular or avascular?
- Articular cartilage= AVASCULAR!! Avascular: relies on the subchondral bone for viability(1) Paired with synovial fluid, coefficient of friction is 0.05-0.02 To put that in context, ice on ice is 0.1 - So very slippery in the joint!! Almost half the friction of ice in a healthy joint of course
Base of Support Look at whole system with transfers
- As long as not touching wheelchair, no longer part of system - Want both people COG over their base of support - Camber being wide increases base of support - When use cane, increase base of support and increase system increasing stability too - Patient likely needs larger base of support with quad cane vs. single point - Calculate this area of contact under wheel to determine how much base of support is
Chart where you have length tension relationship - As tension increases, get to a yield point where it breaks
- As tension increases in ligaments or soft tissues, it reaches a point where it can't take it anymore (Yield point) - Important for joints b/c muscles bring extra stability otherwise ligaments would not be able to take all of the force on their own
- A pivot joint is like?
- BOTH - door knob and revolving door b/c revolves a singular access point - A door knob (b/c neck joint there is one central point that head revolves around) - A revolving door
If something is too heavy and can't eccentrically contract a force that is equal to or greater than the object- what happens?
- Bones slam into one another or your muscle breaks b/c can't overcome that force b/c yield point
Concentric and eccentric often working at same time!!!
- But at times some one is contracting while other is relaxing but usually one eccentrically contracts to protect your joint (antagonist kicks in enough so arm doesn't slap you in face) usually working together in some way even if small - Slowly contract in order to slow motion when lowering wrist down
- Where is the saddle joint?
- CMC joint of the thumb
Lean up against wall and stand with feet against wall and try to reach to touch toes - Fall forward- why?
- Can't shift COG so that it stays over base of support b/c wall impeding that - What happens when not against wall, can correct this by shifting butt back and allowing COG over base of support
Center of Gravity Height • WHAT HAPPENS WHEN YOU REACH FOR YOUR TOES?
- Center of gravity is lower but also outside of the system - If shift COG outside of body, system divided around that COG - just like Using a reacher makes it part of system, shifts COG can throw people off balance
Balance in Upper Motor Syndromes - Stability, a major concern in neurorehabilitation
- Challenges to stability occur on an even basic level as the individual attempts to sit upright and unsupported on a mat table
Squeeze a can of soup, first lightly, then harder - What is happening to the finger flexors?
- Commonly thought beneficial to people with finger osteoarthritis (OA) since joints are not grinding together, but strength is being maintained Isometric= No change in length - So force trying to overcome muscle is SAME as generated by muscle - So if push into wall- will create isometric contraction
- Which myosin bounces up when releases energy (hydrolysis) to bind to actin- now actin is binding with it so releases ADP and phosphate and lets go and keep grabbing new parts of fiber actin
- Constant exchange of ATP - Every time a protein binds it changes and releases and needs to rebind
- How Z discs are pulled closer together and whole muscle contracts and gets shorter - Myosin grabs onto actin and pulls it
- Constant sort of chemical energy causing mechanical change TITIN - protein associated with elastic tension in a muscle
Purpose: ID effects of Ergonomic hand drive mechanism on CTS
- Ergonomic hand drive mechanism helps reduce wrist extension and ulnar deviation when using wheelchairs- reducing risk of CTS decreasing risk of CTS
Cross-Sectional Area of Pennate muscle:
- Fibers run at different angles - For PCS area, cross-section must be perpendicular to the fibers - PCS>ACS Multi-pennate- muscle belly - Fibers come out obliquely like feathers - Physiologic crosses perpendicularly—has more AREA in multipennate b/c more force generated - Anatomic cross section- perpendicular to the tendon at the muscle's largest point - Fibers create the contraction - Matters how many muscle fibers are contributing to that force- so physiologic shows you more about number of muscle fibers and amount of force it produces - More area (cross-section) in the muscle, the more force you can produce - If muscle is bipennate- can cut through it at a diagonal for PCS, more muscle fibers go through this cross-section which tells us there is more fibers to produce force for that muscle - This is more than largest point of muscle (ACS)
So what is an optimal length for the biceps?
- Forearm neutral ***So in b/w 180 (90) of flexion and other joints in neutral This is the optimal range Cross bridges= every time actin and myosin bind it creates these
- Fusiform muscles are built to provide
- Fusiform muscles are built to provide large ranges of motion in pennate muscles, b/c the muscle fibers are oriented obliquely, the actual range of motion, or excursion of the muscle is limited BUT - The force produced by pennate muscles is greater than the force produced by parallel muscles.
So, what would you call the force of the ground on your foot?
- Ground reaction force
Findings: found biomechanic approach alone did not create progress, occupational adaptation approach was more client-centered- ID need for her to master her environment and adapted to use credit card instead of loose change improved occupational performance and provided more motivation
- Have to know when to use different approaches- know what patient needs in addition to their mechanics - not that you are not using biomechanical frame- this is the background, but recognizing needs and addressing those
• IF YOU SHIFT YOUR WEIGHT TO TRY TO RELOCATE YOUR CENTER OF GRAVITY PROJECTION OUTSIDE OF YOUR BASE OF SUPPORT --what happens?
- If gravity projection falls outside of base of support- more likely to fall Center of Gravity Projection • THIS IS THE SPOT ON THE GROUND DIRECTLY UNDER THE FORCE VECTOR OF THE BODY CENTER OF GRAVITY
- If reach up high COG is higher or lower and more or less stable?
- If reach up high COG is higher- less stable - Lower COG, easier for you to remain stable
Active-length tension in another scenario have a little bit of overlap
- In another scenario have a little bit of overlap - a little bit more length though - Not too much crowding, have some space to grab on - Titin is also able to open a little - More tension created here if all myosin is still connecting to actin- same amount of tension happening so same tension but greater length
- The articular cartilage in a joint allows friction that is: less or more than that of ice?
- Less than that of ice on ice
More area (cross-section) in the muscle, the more what is produced?
- More area (cross-section) in the muscle, the more force you can produce - If muscle is bipennate- can cut through it at a diagonal for PCS, more muscle fibers go through this cross-section which tells us there is more fibers to produce force for that muscle - This is more than largest point of muscle (ACS)
Weight and stability?- The force required to accelerate a heavier object?
- More force required to accelerate a heavier object (F=MXA) - (sumo wrestlers demonstrate mastery of stability and weight) - If you are heavier you are more stable
Muscles interact directly with joints to do what?
- Muscles interact directly with joints to perform movements which allow us to participate in functional tasks. Muscles are what keeps us moving and standing - Muscles resist the forces of gravity, allow us to change our posture and positioning to adapt to dynamic environments
Base of Support Look at use of different adaptive devices to look at base of support --like crutches
- Not in our scope of practice with gait but good to know with safety and mobility and decreasing fall risk - With crutches, when both on the ground, just 2 points of contact= base of support and area b/w there- so very small with just crutch tips - Double support with body and crutch tips more base of support here
Wheelbarrow technique - Importance of this technique
- One reason is to lift chair and move it into smaller area if don't have good turn radius, better if tip chair - But BETTER reason is for when chair is empty so don't have to unlock brakes - REDUCE BENDING!!!- reduces effort into it- makes it faster and use wheelbarrow technique
Convex on concave rule
- Osteokinematics and arthrokinematics Go in the OPPOSITE direction - (ex. Shoulder (concave= glenoid, humeral head= convex) humerus downwardly rotates and inferiorly slides whereas the arm moves superiorly)
- As the muscle fiber is stretched beyond its resting length, WHAT begins to contribute to the total force?
- Passive tension begins to contribute to the total force
Ergonomic Intervention O OT recommendations:
- Posture - Tools and personal protective equipment (PPE) - Safety and Team-Oriented approach/ Improve Culture
Golgi Tendon Orgon (GTO)
- Proprioception sensor - Senses change in muscle tension (A>P) Golgi tendon organ - At musculotendinous junction - senses change in muscle tension - Golgi tendon organ= activated by stretch or active contraction of a muscle and that transmit information about muscle tension.
Height changes based on amount of mass in parts of body or system Not just COG height but if think of ourselves like stick figures what happens when we carry a lot of bags on one side - COG changes - Need to compensate for that - Doesn't matter that much if on shoulder or elbow b/c still shifts COG- even though consider moment arm, in general COG shifts - Extra weight Shifts you to that side - Need to compensate that - Ways of avoiding this???
- Put weight on both sides to reduce compensation need - If reach up high COG is higher- less stable - Lower COG, easier for you to remain stable
Do Muscle Activations Ever Occur Alone?
- Rarely. - When you lift or lower a weight you use muscles on one side of your body to perform the task - BUT you also use muscles on the other side of the body for stability Think of the tea pot- tip me over and poor me out When add weight to one side, need to use muscles on other side to stabilize body
- At resting length, the optimal number of cross bridges can form, resulting in what type of force production?
- Results in the greatest force production
Shear
- Shear- Results from force being applied parallel to the surface and produces a tendency for an object either to deform or slide along the surface Can occur when: - 2 parallel opposing forces are applied in the same plane (coplanar) but not along the same line (noncollinear) - And when two oblique opposing forces share the same point of application but are neither parallel nor perpendicular Shear is often accompanied by other stresses (ex. Compression, tension, and torsion)
Wheelchairs • WHEN TIPPING A WHEELCHAIR UP (AS IN A WHEELIE OR TO PULL A PATIENT UP OR DOWN A CURB) THE HANDLES ARE PUSHED DOWN, CAUSING THE FRONT TO LIFT UP. • 5. DOES THE CENTER OF GRAVITY PROJECTION MOVE ANTERIOR OR POSTERIOR?
- Shifts COG back when tipping wheelchair in wheelie position • THIS SHIFT IN THE CENTER OF GRAVITY AND THE PROJECTION HAS TO DO WITH THE SEGMENTAL MASS OF THE HEAD. LOOK IN APPENDIX B TO SEE WHAT PERCENT OF THE BODY MASS IS ASSIGNED TO THE HEAD VS. THE LOWER LEG AND FOOT. HOW ABOUT THE HEAD, NECK AND TRUNK VS. THE THIGH, LOWER LEG AND FOOT? - 60.4% of weight= head and neck and shoulders
What happens is that as speed increase, muscle activation increases - Force increases - So if really trying to lower a heavy item, can't think about it- muscle is gathering up every possible energy to try and protect you so don't hurt self - So as going really fast to lower it, trying to increase force to protect self - So as load increases, WHAT increases in ECCENTRIC contraction??
- So as load increases, velocity increases in ECCENTRIC contraction - Greater force produced when cross bridge is pulling apart like Velcro here - Cross bridges are able to generate more force (maybe more passive force when releasing) - there is a rapid reattachment of cross bridges - Easy to picture actin and myosin like Velcro- if pull it apart quickly or rip of bandaid - creates more force
COG generally follows a very predictable trajectory when looking just at COG
- So for bat, COG is closer to where the most mass is, COG follows this certain perfect arc - Same with a wrench - lighter weight on end sort of spins around COG - When you drop something, it also has a consistent downward trend of COG despite how the other parts of object move differently
Active-length tension In the case where there is too much crowding
- So muscle here is too shortened, length is too low, tension CANNOT be produced, so length is 0 - voltage difference- polarity of actin doesn't allow anything to connect to it- if trying to pull a cart with too many people close together, can't do any work b/c too close - So myosin can't connect with any acting b/c of overlap here and no space for titin to stretch here
- When sitting or standing in a closed chain movement, the moving member is convex femur --so what happens with the osteo and arthrokinematics?
- So the convex femoral member is moving ON the concave tibial member- osteo and arthrokinematics are in the OPPOSITE direction
Leverage=
- So the farther from the joint (a greater distance) requires less force to cause damage - The closer you are to a joint (a lesser distance) requires MORE force to cause damage
Base of Support DURING STANDING, HOW IS THE BASE OF SUPPORT DIFFERENT WHEN THE CRUTCHES ARE LINED UP WITH THE FEET VS. WHEN THE CRUTCHES ARE POSITIONED IN FRONT OF THE FEET?
- THE BASE OF SUPPORT IS REDUCED WHEN THE FEET ARE IN LINE WITH THE CRUTCH TIPS.
******Need to address joint FIRST before starting strengthening
- THE JOINT ALWAYS comes first!!- doesn't matter how strong you are or the tendons - If joint comes stiff, muscles probably won't overcome this
Remember in most cases: treat the joint first!
- THE JOINT ALWAYS comes first!!- doesn't matter how strong you are or the tendons - If joint comes stiff, muscles probably won't overcome this
Third Class Levers The following are always true of third class levels:
- The axis of rotation (fulcrum) is on one end - • Both the resistive force and the applied/effort force are on the same side of the axis of rotation (fulcrum) § The forces act in different directions • Moment arm of the applied force (IMA) is shorter than the moment arm of the resistive force (EMA) - § Therefore mechanical advantage is always < 1 (mechanical disadvantage) • Examples § Musculoskeletal: bicep curl § Non-musculoskeletal: broom • Most of our muscles are third class levers
Purpose- Compare two interventions to improve posture and reduce pain in people with computer based jobs---real-time intervention vs. one time postural training
- The more feedback helped correct themselves than just education in postural training people received real-time intervention had significantly reduced pain biofeedback showed sig. spine angle improvements at T1 and T2 and at cervical spine angles
torque
- The product of a force (F) and its moment arm - can be considered as a rotatory equivalent to a Force - A torque is described as occurring AROUND a joint in a plane perpendicular to a given axis of rotation - A torque ROTATES an object around an axis of rotation Internal torque - The product of the internal force (muscle) and the internal moment arm (D) - IF X D - Has the potential to rotate the forearm around the elbow joint in a counterclockwise or flexion direction Internal moment arm- perpendicular distance b/w the axis of rotation and the internal force External torque= the product of the external force (such as gravity) (EF) and the external moment arm (D1) - EF X D1 - Has the potential to rotate the forearm around the elbow joint in a clockwise or extension direction
What is the difference in the tilt point (casters on and off) and why?
- The tilt point is located FARTHER back with footrests on b/c the footrests shift the COG of the system forward - This is because the tilt point needs to move the COG over the base of support
Diagrams show how force changes b/c of gravity or mass changes On Earth gravity is the SAME everywhere so stays constant Variations in weight= due to mass Increase mass, increase weight and vice versa Difference b/c gravitational force on the moon?
- These equations show difference b/w gravitational force of the moon and Earth THE GRAVITATIONAL FORCE IS DIFFERENT ON THE MOON! - So why we weigh less on the moon b/c gravitational force is less!!
Actin and myosin proteins like to do 2 things- what are they?
- These proteins: 1) they like to bind to certain stuff 2) they change shape when binding or unbinding
b/c of their elastic nature, muscles ALSO produce force PASSIVELY
- Titin is your passive extensibility- keeps myosin structurally sound (in place where its supposed to be) so muscles in this way, are similar to a rubber band - Like a rubber band a muscle generates greater internal elastic force when stretched - This elastic behavior= demonstrated by a muscle's passive length-tension curve
Rotary motion vs. linear motion How are they different?
- Translatory motion: All parts of the object move the same distance in the same time. Movement in a straight line. - Example: scapular elevation/depression. Protraction/retraction on the rib cage. - Rotatory motion: All parts of the object move through the same angle in the same time. Angular motion. Muscle contraction may cause a joint to exhibit rotational motion.
Weight: A vector or a scalar?
- W= MG - G= 9.8m/s2 - Gravity is a force that acts toward the center of the Earth and results in constant acceleration on any object (including our body) Weight= a vector b/c it possesses both magnitude AND direction
Active-length tension What matters in active-length tension???
- What matters in active-length tension= SARCOMERES!!! - Now talking about your muscle power to create this curve - Where force of contraction matters
Pennation angle - When 0 deg: vs. - When >0 deg:
- When 0 deg: all fibers parallel to the tendon ~100% of force generated by muscle is transmitted to the tendon and across the joint - When >0 deg: fibers are oblique to the tendon Only a portion of the force is transmitted through the tendon ****Note how the tendon goes through the entire muscle!
- Mitochondria live on sarcolemma of muscle cell - ATP = energy source of the cell
- When AP opens up Ca+ channels via T tubules - ATP and Ca2+ flood in - Myosin wants to touch actin so when Ca+ comes in , myosin can now get closer to the actin b/c Ca+ binds to troponin and it changes shape
Is the elbow a perfect hinge?
- When looking at an elbow too (hinge joint) - What other directions go with this b/c not a perfect hinge- have a CARRYING angle- there is a bit of a change there - Women have a bigger carrying angle than men - So when flex up, its angled a little bit more toward your face when you flex
During closed chain movement at the radio-carpal joint, which rule applies?
- When my hand is planted and my arm is moving, which joint surface is moving? - Radius is moving - Concave is moving ON the convex segment (same) direction So when you move your hand its different b/c radius is relatively fixed and carpals are moving on concave radius - So that would be convex on concave (opposite) motion
Base of Support
- Wider/larger= more stability - Wider base of support, more stable, - - Consider COG over base of support here
Muscles resist the forces of gravity, allowing us to do what?
- allow us to change our posture and positioning to adapt to dynamic environments
Tennis ball and bouncy ball fall at the same acceleration--why is this??
- b/c even though masses are different, and weight are different, but acceleration of gravity is constant so they hit the floor at the same acceleration
Skeletal Muscle Structure § Muscle-tendon unit== why is this?
- b/c tendon goers through entire muscle from origin to insertion - Muscle fibers come off of tendon
Collagen and elastin= fibrous proteins - collagen=
- collagen= tighter part, resists stretch and supports joint Type 1 collagen: thick, rugged fibers with little stretch Type 2 collagen: thinner, providing a framework for shape and consistency of structures Collagen type 2= easier to damage from outside forces - (ex. Tendons have more elastin than collagen but always a combo of both in CTs and tendons)
Active insufficiency - Talking about tendon or muscle that crosses more than one joint - So if tie band to finger and stimulate FDP - crosses 4 joints - Crosses wrist, MP joint and everywhere in hand - - First joint it crosses Flex wrist - already crowds a lot Sarcomeres are too short, everything is too crowded so what results??
- crowded so not enough force available to bend fingers - If create passive tension (wrist extension), contributes to total tension available to - Think of lengthen - tension curve - Creates passive tension when wrist extends back - When a muscle contracts- can only shorten so far - So need to make sure pt is in an optimal way to do that
Any time a muscle is being lengthened while fighting an outside force, it is doing what?
- eccentrically contracting (gravity is usually the outside force) - Concentric and eccentric often working at same time - But at times some one is contracting while other is relaxing but usually one eccentrically contracts to protect your joint (antagonist kicks in enough so arm doesn't slap you in face) usually working together in some way even if small - Slowly contract in order to slow motion when lowering wrist down
Can activate different parts of a muscle based on O & I and different heads
- ex. Pec is big fan muscle - If open chest with ER, get more sternal pecs b/c coming from that direction, if go up higher get more costal fiber activation - So line of pull matters
In Z discs we have thin filaments (actin) and thick filaments (myosin
- have heart shaped heads - Myosin always wants to get with actin - Duo of proteins so in love- myosin always wants to touch the actin - Barrier- tropomyosin lives on the troponin binding site on actin- like the body guard - Troponin and tropomyosin
- When the muscle is further stretched, farther beyond its resting length, what accounts for most of the total force?
- passive tension accounts for most of the total force
Collagen and Elastin (Foreign people (CE) Elastin: what do you think this is like?
- wants to increase flexibility of tissues - (ex. Tendons have more elastin than collagen but always a combo of both in CTs and tendons)
Second Class Levers The following are always true of second class levels:
- • The axis of rotation (fulcrum) is on one end - • Both the resistive force and the applied/effort force are on the same side of the axis of rotation (fulcrum) - The forces act in different directions • Moment arm of the applied force (IMA) is longer than the moment arm of the resistive force (EMA) - - Therefore, the mechanical advantage is always > 1 • Examples - Musculoskeletal example: tiptoe - Non-musculoskeletal: wheelbarrow
- What are general recommendations for a "good position" during any activity?
--TENODESIS --Elbows at 90- good for when working in front of body If working on fine motor vs. gross- fine motor should be closer to eyes- gross is about control and having good alignment and maintaining good length of muscles Bending at the knees is good- some cases you would not want to bend knees pretty activity -dependent-- squatting uses more energy but saves your back- the more susceptible part of injury ---Maintain natural curves of back - thoracic, cervical, lumbar, and sacral curves- more important than keeping back straight Shoulder away from ears ---Tight core to protect back Tenodesis??- wrist extension and grip? Flexing of the fingers through tendon action of the extrinsic finger flexor muscles when they are stretched across the wrist joint during wrist extension. This mechanism is used for functional grip
Active vs. passive insufficiency recap
-Active insufficiency both joints are doing action that the muscle does- agonist at elbow and agonist at shoulder- makes it more challenging b/c shortening too much -Passive insufficiency if cross more than one joint, can't stretch it over these joints as easily - -Shoulder extended, elbow extended, forearm pronated= example of passive insufficiency
Scalar= magnitude and no direction Different types of data points we work with
-Just a magnitude (#) NOT a direction - -Things that define a data point but more of a quantity -Mass -Speed -Time - -Mass= a quantity (scalar) vs. Weight= a vector(quantity and direction- to quantify it)
-Another example of a first class lever= scissors -(EFL) - -What could you do to make scissors easier for yourself?
-Make the effort moment arm LONGER!!! -If you bring the effort out longer (increase the IMA you are using) and a shorter EMA (load) increases your MA -Easier to cut with material placed in scissors closer to axis -Placing your effort farther away in handles, you are increasing your IMA think of it like a teeter totter - -This is why MA can be equal, less than or greater than ONE- equilibrium is like a teeter totter where both sides= balanced
1st class levers= Like the neck Have to know where the COG is in a human to understand where this works - COG (weight of head)= This is the LOAD - where the weight of the head is having the effect What is the effort in this example?
-The effort in this example= muscle contraction -Neck extensors contracted to hold head up - -If someone has a forward head- the load wins the battle_ brings COG forward- IMA= shorter so MA is given to EMA (load) has the leverage here and wins
Mechanical advantage (AKA leverage) -Talking about the moment arm- distance from axis of rotation When farther away from an axis of rotation have more or less leverage?
-When farther away from an axis of rotation- have MORE leverage -Know that already -This is going into the "WHY" this is the way it is - -MA= same thing as LEVERAGE - -Think of a door hinge or a revolving door - -If put door knob at center of door, requires more force to push/pull it open -So increased distance (Moment arm) increases leverage - -To calculate the Moment (TORQUE) = force X distance (moment arm)****** really important to remember - -Moment= force X distance (moment arm) - -If the force is the same (ex. Both weight ten pounds) then increased distance determines the winner -If the force is not the same, have to shift this around
Active and Passive Insufficiency
-active - if a muscle is shortened, it can't generate max force -passive - if a muscle is fully lengthened, it can't lengthen anymore and produce max force in between (slight extension) = greatest amount of strength
total length tension curve
-passive and active together -as muscle fiber is further stretched, passive tension dominates curve (lengthened and weak) - The longer your muscle is, the more the tension is passive - Like when you stretch a rubber band, just wants to snap back - So looking at total force muscle is capable of producing in addition to the passive force built up - Stiffness and contracture affects the curve- may not be able to get to optimal length to produce force - ***Passive is always part of active in some way- so should think about length-tension curve - Not always using active when using passive
Using THE BIOMECHANICAL FRAME OF REFERENCE • With respect to physical performance, OTs work with their clients to improve physical performance by??
1) conditioning/retraining, 2) or adapting the environment.
Differences between rotary and linear motion:
1. Rotary motion occurs in a circular path around a central point, the center of rotation (or the axis of rotation). Linear motion occurs along a linear path, starting in one place and ending in a different place. 2. Objects that rotate change orientation during movement. Objects in linear motion remain in their original orientation throughout. 3. Two points in a segment moving around an axis move at different speeds, the point farther from the center of rotation moves faster than the other. Two points in a segment moving in a line from one place to another move at the same speed. Ex. Baseball, Tennis, walking - Distal parts (the extremities; hands and feet) travel greater distances at faster speeds (favors locomotion and manipulation)
The Wheelchair Independent Measure (WIM) uses a _____ point scale to determine level of independence in wheelchair users. 3 5 7 10
7
Yield point
A tissue that is elongated BEYOND its physiologic range eventually reaches its YIELD POINT- stress at which a material begins to deform plastically
What is an example of a second class lever? A wheel barrow A scissors Swinging a baseball bat A seesaw
A wheel barrow
Which of the following best describes an antagonist? A) A muscle or group that opposes the action of the prime mover (agonist) B) A muscle that always shortens when active C) A muscle that fixes or holds the body segment stationary so that another muscle can more effectively perform an action D) A muscle or group that is most directly responsible for performing a particular action
A) A muscle or group that opposes the action of the prime mover (agonist)
The term active insufficiency describes A) Decreased ability of a two-joint (multi-articular) muscle to produce a significant force to complete an action because it has become too short B) A muscles inability to perform an action because of tightness of it's antagonist C) The inability of an action to be completed because the antagonist is stretched over multiple joints D) When two or more muscles combine forces but fail to complete an action
A) Decreased ability of a two-joint (multi-articular) muscle to produce a significant force to complete an action because it has become too short
A muscle with a line of pull anterior to the medial-lateral axis of rotation of the shoulder will perform: A) flexion B) extension C) abduction D) adduction
A) flexion
Try This Exercise... • TRY TO SHIFT YOUR CENTER OF GRAVITY PROJECTION BEYOND YOUR BASE OF SUPPORT. • LEAN TO THE RIGHT AS FAR AS YOU CAN (WHILE STANDING). DO YOU NOTICE ANY MASS SHIFTING?
AS I LEAN TO THE RIGHT, MY LEFT ARM MOVES FARTHER LEFT, MY HEAD SHIFTS A LITTLE TO THE LEFT. IN OTHER WORDS I AM SHIFTING MY SEGMENTAL MASS (ARM & HEAD) TO SHIFT MY BODY CENTER OF GRAVITY TO THE LEFT TO PREVENT THE CENTER OF GRAVITY PROJECTION (ON THE GROUND) FROM MOVING OUTSIDE OF THE BASE OF SUPPORT. - If try to stand and reach outside of base of support - Functional reach test= tests this - how far can reach Gravity projection beyond base of support - - Measure that distance
The force of gravity (Fg) is equal to mass times acceleration, Fg = ma
Acceleration due to gravity is a constant, g = 9.81 m/s2 --> Fg = mg This force is the weight of an object (force produced by gravity on mass) 9.81 m/s2 = acceleration due to gravity - gravitational constant (G)
Feedback Loop Afferent
Afferent: Arriving in the CNS - Sensory information - AND information from muscle spindles
Muscles follow that rule that if you put your face like that it will stay that way So muscles can shorten long term AND lengthen long term Changes whole mechanics of body
All contractions assume work is being done- - Concentric- Go from lengthened position to shorten position- sarcomeres and z discs coming together
Which of the following motions occurs around a vertical axis of motion? All of them Rotation of the radial head External rotation of the hip Internal rotation of the shoulder
All of them
Open and Closed PACKED Positions What is it called when a joint is able to move in directions outside of it's normal parameters? (like the humeral-ulnar joint rocking side to side)
Answer: Accessory joint movement or joint play (slight, passive, nonvolitional movements allowed in most joints (also called joint play).
Workspace analysis - cluttered desk with phone answering
Awkward neck posture Workspace is not ideal - not a lot of space to move Restrained to a small space to write notes Affects overall posture b/c unconsciously working around everything else Forward shoulder and hunch neck posture Table could be brought up a little higher Two hands on tool- makes it easier to exert force but less control Squatting vs. standing
Ergonomics as applied to different performance areas ---Basically everything you can take and analyze in day to day life and think of how to make it better If tool is uncomfortable- usually a prompt to explore it further
Bicycles= v. biomechanically design and should be adjusted to fit the person Just like any tool should be designed to fit you specifically Really supposed to think of skis fit for you specifically
Joint type-Condyloid Primary Angular motions Mechanical analogy Anatomic examples
Biplanar Mostly spherical convex enlarged in one dimension, and a shallow concave cup Metacarpal phalangeal Tibiofemoral (knee)
Joint type-Ellipsoid Primary Angular motions Mechanical analogy Anatomic examples
Biplanar motion (flex/ext and abd/adduction) Flattened convex ellipsoid and concave trough Radiocarpal
Joint type-Saddle Primary Angular motions Mechanical analogy Anatomic examples
Biplanar, spin between bones possible but limited Reciprocal concave/convex surfaces, like a horse rider and saddle Thumb Carpo- metacarpal (CMC)
• GENERAL RULE FOR COG LOCATION of non-uniform objects? COG lies closer to what?
COG OF NON-UNIFORM OBJECT LIES CLOSER TO THE END WITH THE GREATEST MASS COG in Non-uniform objects - COG = the MEAN location of all mass in a system - General rule for COG of non-uniform object - COG lies closer to the end with the greatest mass
Segmental Centers of Gravity
COG for each body segment as a percentage of distance from the distal and proximal ends of the segment
Ergonomic Intervention O Stretch and Exercise sessions O Rest-work balance O On-site therapy O Palliative cares/ first aid O Stress management/ wellness workshops O Workstation redesign
Can lead stretches before employees start the day Rest-work balance- making sure not pushed beyond physical capacities - ex. Google has nap pods- make employees more productive - On-site therapy - Palliative care- more like first aid response- like wound and aches and pains - Some things we are allowed to provide to employer without calling it a work injury - providing things if one complains of mild elbow strain at work -ex. Give ice break, ibuprofen, wrist splint, person does not have to claim anything yet- makes employer look better- caring for aches and pains early on avoids full-fledged injury - Stress management!! / wellness workshops
Center of Gravity • COG OF A SYSTEM OF MASSES (EX: MOBILE, HUMAN BODY) IS THE POINT WHERE THE SYSTEM CAN BE what??
Center of Gravity • COG OF A SYSTEM OF MASSES (EX: MOBILE, HUMAN BODY) IS THE POINT WHERE THE SYSTEM CAN BE BALANCED IN A UNIFORM GRAVITATIONAL FIELD • FIND COG FOR VARIOUS PARTS AND SUMMATE • WHEN STANDING UPRIGHT, COG LIES IN THE ABDOMINAL CAVITY ~6 INCHES ABOVE THE PUBIC SYMPHYSIS (anterior to sacrum)
Center of Gravity • IN SYMMETRIC, UNIFORM OBJECTS, (SHAPE AND MASS DISTRIBUTION) THE COG IS LOCATED WHERE??
Center of Gravity • IN SYMMETRIC, UNIFORM OBJECTS, (SHAPE AND MASS DISTRIBUTION) THE COG IS LOCATED AT THE EXACT CENTER OF THE OBJECT (EVEN IF THERE IS NO MASS THERE) COG= CENTER OF MASS (COM) IN UNIFORM GRAVITATIONAL FIELDS • HOW LOCATE? • DIVIDE THE OBJECT INTO EQUAL HALVES IN ALL 3 PLANES • FIND THE POINT WHERE THE 3 PLANES INTERSECT
Center of Gravity Projection--what is this?
Center of Gravity Projection • THIS IS THE SPOT ON THE GROUND DIRECTLY UNDER THE FORCE VECTOR OF THE BODY CENTER OF GRAVITY • IF YOU ARE STANDING UP STRAIGHT, IT IS LOCATED PRETTY CLOSE TO THE SPOT IN THE MIDDLE OF YOUR FOOT PRINTS ON THE GROUND (YOUR BASE OF SUPPORT) • IF YOU SHIFT YOUR WEIGHT TO TRY TO RELOCATE YOUR CENTER OF GRAVITY PROJECTION OUTSIDE OF YOUR BASE OF SUPPORT YOU ARE MORE LIKELY TO FALL! Gravity PROJECTION - If gravity projection falls outside of base of support- more likely to fall
Cell types in a joint-chondrocytes
Chondrocytes: cells of the cartilage (recall medical terminology) ---BOTH chondrocytes and fibroblasts are also responsible for maintenance and repair of tissue Both responsible for maintenance and repair- pull out inflammatory cells and bring good ones in generally
Muscle Activity § Concentric § Isometric § Eccentric
Concentric Contractions Energy expending process that results in shortening of muscle fibers Isometric Activation Energy expending process in which the length of muscle fibers does not change - Muscle fiber does not get longer or shorter to produce force Eccentric activation Energy expending process that results in lengthening of the muscle fibers Generates the greatest force
About the SPEED of contraction Concentric contraction - as velocity (speed) increases- if try to lift something quickly- force capable of generating is what?
Concentric contraction - as velocity (speed) increases- if try to lift something quickly- force capable of generating is LOWER As you are speeding up in shortening the muscle, cross bridges cannot connect fast enough so force decreases Muscles can't work as hard when trying to do it fast- doesn't create as much force
Purpose: improve student transfer training in acute setting assessed on proper body biomechanics
Conclusion- 66-88% of transfer items were done correctly so student noted benefits from training but needed to reinforcing of proper body biomechanics
Purpose- apply data to determine if splint affects UE compared to non-affected side- mostly shoulder here during Stacking with wooden blocks, and pouring task
Conclusions- In people with orthotics- Increased motor unit recruitment to compensate with lack of movement in the wrist - Compensation patterns cause lots of pain Stacking task had more shoulder abduction with orthosis- resulted in compensation patterns Abduction and flexion more than shoulder with orthosis in pouring task
Does acute muscle stretching help kids with CP
Conclusions- dorsiflexion angle was increased in self-stretch and physiotherapy stretch - Muscle lengthened and tendon lengthened and muscle fascial length also stretched --yes stretching was beneficial
Purpose: wanted to see if there was a connection with music work being done and neck/shoulder pain and difference b/w men and women
Conclusions- more women had neck and shoulder problems - more pain overall for women - all have some type of discomfort Concepts - COG is different of men and women, women is lower
Purposes- are there differences in muscle activation and control of using hand vs. reacher???
Conclusions- there are differences in what muscles are used when using a reacher vs. not *****Need to make sure there is adequate training time before giving Ae, need for more clinical reasoning in understanding which muscles are needed - Used EMG data to record which muscles were activated and by how much - No physical disabilities in subjects
Shoulder vs. Hip joint
Coxofemoral joint= deeper socket so farther from the surface, more able to pop to each side w/o dislocating GH joint= shallower socket so closer to the surface, less able to pop without dislocating - Oiling socket with Vaseline mimics synovial fluid reducing friction and producing smoother movement
Crumpled ball of paper falls faster than a flat sheet of paper b/c of what??
Crumpled ball of paper falls faster than a flat sheet of paper b/c of AIR RESISTANCE Have the same mass, but air hits the flat paper differently and causes it to change direction (flat paper has a larger SA, so has increased air resistance) - Air resistance (AKA drag) • A TYPE OF FRICTIONAL FORCE OPPOSING MOTION • ACTS IN OPPOSITE DIRECTION THAT THE OBJECT IS MOVING • ALL MOTIONS • FALLING FROM SKY: APPLE (PAPER DEMO) • MOVING ALONG GROUND: CAR (HAND OUT CAR WINDOW "DEMO") • Air resistance - INCREASES WITH INCREASED SURFACE AREA (DEMOS)
Leverage umulative strain example: Riding a bicycle with prolonged pressure on the distal aspect of the first metacarpal.
Cumulative strain example: Riding a bicycle with prolonged pressure on the distal aspect of the first metacarpal. Farther from the joint requires less force to cause damage
EXCURSION - AKA?
EXCURSION - AKA range of motion §Muscles can shorten only a limited distance - § they have limited excursion capability Excursion (means shortening for a muscle)
- Have to lengthen a muscle but in order to slow it down, constant twitching happening so generates more force than when picking an object up--this describes which activation?
Eccentric activation - If you have lifted an object or in a shortened position and a heavy object gets put into your hand, muscle with create enough force to overcome that and slow it down as you lower it down - To protect self, muscle will lower it slowly so force generation is in line with resistance of object- more than when you lift something up
Eccentric is always going to generate more or less force?
Eccentric is always going to generate the greater force than isometric and concentric
Feedback Loop Efferent:
Efferent: Exiting the CNS - Motor signals - But there's a sensory component we should explore further Muscles One nerve and one artery and vein dedicated to it - When brain comes to anterior horn cell to muscle fiber, sensory fiber and muscle fiber actually talk to each other so sensory fiber help determine what length is- you can feel this when you are stretching
First class levers Example: pushing wheelchair up a curb.
Effort = tipping wheelchair back Fulcrum= axis of rotation of wheelchair Load= man's weight (ex. Of a first class lever) - To raise the front wheels: push down on the handles, pivoting around the contact between wheels and the ground. The contact point of the wheels with the floor is the fulcrum (axis of rotation). Pushing force downward is the effort. The weight of the patient and the wheelchair is the resistance
3 classes of levers
Effort, load, fulcrum -Look for fulcrum first -Then look for load and effort - Class 1 - Like a teeter totter or seesaw EFL or LFE Class 2 - ELF= Effort, load, fulcrum Class 3 - FEL= Fulcrum, effort, load
Elbow flexion strength is greatest in what position?
Elbow flexion strength is greatest at MIDRANGE of elbow flexion, a joint angle associated with maximal overlap of cross-bridges w/n the muscles - Elbow flexion strength is LEAST at both extremes - b/c strength of elbow flexors is expressed clinically as torque, both muscle force and internal moment arm need to be considered
Client Centered Ergonomics
Emphasizes fitting the work to the worker according to the conditions of a particular workplace O Increased client participation has been associated with more effective results and increased client satisfaction O Therapists who do ergonomic analysis should have years of experience treating musculoskeletal disorders (outpatient, work hardening, industrial rehabilitation) **- Therapists do not NEED to have lots of experience treating - does help but not required - Should be considering the culture and environment, not just risk factors in a musculoskeletal way Even though trying to be very client centered- not going into a workplace looking at how one person does something - One person won't give you all the info - Lately research trying to aim for universal design make general-low risk for 75% of people - Then interventions for individual people - like use a different tool to make task better designed for them - If someone is taller, some techniques may not be beneficial for them
Isometric activation
Energy expending process in which the length of muscle fibers does not change - Muscle fiber does not get longer or shorter to produce force Squeeze a can of soup, first lightly, then harder - What is happening to the finger flexors? - Commonly thought beneficial to people with finger osteoarthritis (OA) since joints are not grinding together, but strength is being maintained Isometric= No change in length - So force trying to overcome muscle is SAME as generated by muscle - So if push into wall- will create isometric contraction - If push hand into a fist, once get to end of this range, no more activating happening- NO lengthening or shortening happening - ALL OF THESE REQUIRE ENERGY - Squeezing a can of soup - good for people with arthritis
Eccentric activation
Energy expending process that results in lengthening of the muscle fibers Generates the greatest force Most used functionally when lowering a load or slowing a motion Also helpful in protecting joints from damage by forced, rapid motion When force outside is MORE than what you are If trying to lower a heavy object to the ground
Concentric Contractions
Energy expending process that results in shortening of muscle fibers How people generally think about muscles working Doing a curl, showing off muscles The term "contraction" is used synonymously with activation, but technically it should only apply to "concentric" since it implies shortening What we think of when muscles are showing- when you flex Showing off your guns But contraction is only used for concentric b/c implies shortening (why we also use contracture In dysfunctionally shortened position) Contractures Muscles follow that rule that if you put your face like that it will stay that way So muscles can shorten long term AND lengthen long term Changes whole mechanics of body All contractions assume work is being done- - Concentric- Go from lengthened position to shorten position- sarcomeres and z discs coming together
Ergonomics Team Ergonomics services are best delivered by a team of collaborative professionals:
Engineers O Nurses O Rehabilitation Professionals O Job managers O Workers Add in safety people too - May be OSHA directly (safety accreditation people basically) - That's why factories have # of days injury free
Pre-employment Physicals
Ensures there is a good fit between the employee and the physical and psychological demands of the job O Reduces liability on the company for physical limitations present prior to starting employment O Stop-light approach (Blankenheim Services) Stop-light approach- like caution/hazard on WISHA checklist - Will check flexiblilty in hamstrings- if contracted at certain level will give them a red light, if perfect flexibility will give them a green - 3-4 hour session to evaluate what your risk factors are - Good for ID if you are fit for the job Good for employer too b/c tells you what injuries you came in with on the job
A field focused on prevention & wellness Basically making sure things doing at work are ergonomically correct--what is this??
Ergonomics (also called human factors)So things that you can control are fitting with the job to decrease load on the body O A field of study focusing on work performance with an emphasis on worker safety and productivity, fitting the worker to the job O A design philosophy that focuses on supplying a product (or setup/procedure) that ensures safety, ease of use, comfort, and efficiency **** A field focused on prevention & wellness Basically making sure things doing at work are ergonomically correct
Client Centered Ergonomics O Emphasizes fitting the work to the worker according to the conditions of a particular workplace O Increased client participation has been associated with more effective results and increased client satisfaction O Therapists who do ergonomic analysis should have years of experience treating musculoskeletal disorders (outpatient, work hardening, industrial rehabilitation)
Even though trying to be very client centered- not going into a workplace looking at how one person does something - One person won't give you all the info - Lately research trying to aim for universal design make general-low risk for 75% of people - Then interventions for individual people - like use a different tool to make task better designed for them - If someone is taller, some techniques may not be beneficial for them - Therapists do not NEED to have lots of experience treating - does help but not required - Should be considering the culture and environment, not just risk factors in a musculoskeletal way
Factors in Job Analysis O Muscular work O Control of movements O Efficiency O Body mechanics and force factors O Design of workstations O Heavy work & handling loads O Fatigue O Occupational stress & mental activity O Night work and shift work O Vision, noise & vibration, lighting O Psychosocial factors --ex. how to best carry 8 cartons of chemicals
Ex. Drag a cart full of 8 cartons of chemicals instead of carrying them each time- take away arm strength but bring in loud noises and causes lots of vibrations into the arm - Understand you can solve something but may have another problem to deal with
Third class levers- rules
FEL***One most common in our human muscles Load has advantage over us MA is always less than one This is how most of our muscles work (ex. Biceps= axis of rotation = very close to biceps insertion) Moment arm of load is way out by books So our biceps have to work harder than the load
Recall Newton's Laws Newton's 3rd law:
FOR EVERY ACTION THERE IS AN EQUAL AND OPPOSITE REACTION • EX: GROUND REACTION FORCES 3rd=every action has an equal and opposite reaction
A closed chain motion refers to the distal segment of a joint moving on a relatively fixed proximal segment True False
False
Flexion of the hip occurs in the frontal plane True False
False
A muscles excursion refers to the maximal force the muscle can produce - True or False
False! Muscles are constantly being lengthened or shortened- this change in the length of a muscle (AKA Range of motion)
Purpose- Does the fit of furniture relative to child's size have impact on child's object manipulation skills
Findings- YES! - Specifically complex manipulation were more affected by child seated position than well-established skills - Should seat kids in optimal positions when completing complicated hand tasks
*******Purpose: ID musculoskeletal symptoms in parents of children less than 4
Findings: 66% of parents had musculoskeletal pain in lower, upper back and neck b/c of immediate demands of child - Parents 0-2 children had most high risk of injury and pain *******Parent participating in a hobby at least once per week for an hour reduced musculoskeletal pain - Mothers who worked 10-20 hours a week had more pain b/c of role cross-over - The older the child gets, less risk b/c less motion required to care for child as they get more mobile
Purpose: want to see how much force is involved in lateral patient transfers - Compared using a bedsheet with a circular tubular sheet, and a smooth mover- like a backboard
Findings: bedsheet- 32 kg of force needed, backboard smooth mover only 22 kg, 18.7 kg needed for sally mover - Devices significantly reduced force needed to perform lateral transfers - These devices Reduce friction b/w surfaces causing for less force required for transfer
Purpose: evaluating effectiveness of AE in bathroom impacting balance in bathing transfers
Findings: during bathroom - vertical grab bar increased control and posture, horizontal grab bar increased time b/w points of contact decreased control, and parallel to movement bath mat didn't reduce variability but perpendicular bath mat did help with balance Direction of equipment needs to be perpendicular to movement to help balance
Purpose: ID difference b/w force supports systems for people with hemiplegia experiencing subluxation - Differences b/w Use lap tray, sling
Findings: first sling had loops under affected forearm w/straps over both shoulders- more than half of weight of effected arm loaded on affected arm, another sling attempted to offset force on affected arm by moving to unaffected shoulder, bobath increased overall stress on shoulder structures
Purpose: typical and robot training are beneficial but which ones are better for a specific patient
Findings: for mild to moderate stroke patient- - Biomechanics of each depend on what stage your patient is in b/c high satisfaction for both treatments - Robot= less intense and requires less strength- good for beginning of treatment - TST= better for further along in treatment found muscle activity to be higher in task specific b/c arm supported by robot, robot was also kept to be at shoulder level, TST had higher repetitions and higher pain level
Purpose: prevent low-back pain in young workers
Findings: group with training can be effective to have less lower back pain
Purpose: Determine effectiveness of robots in improving functional abilities of stroke patients
Findings: intensities of conventional therapy therapist and robot are the same- but if therapist is limited in time, robot makes up difference
Purpose: biomechanical demands of a virtual vs. physical keyboard
Findings: lower forces were required when using virtual keyboard in all aspects, but productivity was much lower with these individuals
Purpose: measure efficacy of lower body mechanics instruction on people with and without lower back pain- work hardening program
Findings: major increase in lifting strength in participants after work hardening program, work efficiency INCREASED and had differences in body in these participants too Intensive body mechanics instruction had impact on endurance, positioning, and work in general
Purpose: wanted to see if foot orthoses do support balance on child with CP , tested with and w/o orthosis
Findings: orthosis did not affect standing or gross motor, but it did help him go down from tip toe position to stand w/heel gave him more balance helping with fine motor movements
Purpose: importance of synovial fluid and friction with joints
Findings: patients with RA have decreased synovial fluid which causes less gliding and can lead to bone on bone contact -leading to pain and abnormal posture and poses in wrist Of looking at biomechanical forces, OT can use these principles so people can go back to their normal functioning
Purpose: determine individuals lifting capacities and proper body mechanics - want to ID a shift from safe to unsafe lifting style
Findings: pre-definition most people had good biomechanics but once reached defined lifting capacity majority had unsafe lifting styles
*****Purpose- compare heart rate for slumped vs. erect posture in different tasks
Findings: proper body mechanics actually increased heart rate in erect postures-thought b/c increased musculature contraction for posture - putting more demand on the heart- opposite of what they thought ****Sitting upright will actually increase heart rate if muscles are untrained - Increased Slightly for reading upright vs. in awkward posture
Purpose: find effects of cutaneous feedback (proprioceptive part) of hump position of mouse, raised in front or back
Findings: shorter time for rear hump mouse Both dorsal wrist splints and rear-hump mice are recommended. Length of index finger positively correlated with task performance.
Purpose: looked at 3rd graders writing in Hebrew wanted to see how ergonomics affected handwriting and if difference b/w proficient and non-proficient hand writers- posture, grip and pencil positioning
Findings: significant correlations b/w biomechanical factors non-sufficient handwriters had poor body mechanics, forward head, slumped shoulders, switched hand posture often We should be looking at whole body mechanics not just handwriting mechanics
Purpose: determine whether hippotherapy increased participation in kids with ASD
Findings: substantial improvement in postural stability of kids with ASD- receptive communication, coping and participation in ADLs
****Purpose: lower body mechanics and pencil design effect on kids with CP
Findings: use of pelvic belt and lower leg strap could control postural adaptations and improve handwriting grip and efficiency - Grip height would effect shoulder level in writing, affecting compensation patterns *****Z-shaped pattern of pencil ensures fingers do not obstruct field of vision eliminated head/neck inclination
Purpose: show two different parts- different learning style inventory and proactively screen patients to ID learning style of each patient and design protocol
Findings: very positive- if used 14 day protocol on their patient, overall outcomes were better if they didn't - they ID barriers to occupational performance and ID most effective learning styles that results in better functional outcomes
Purpose- investigate effects of using a splint for 8 weeks for daily activities full time and seek desire for surgical intervention
Findings: wrist splint wearers had less CTS syndromes and opted to NOT have surgery, control group still wanted surgery b/c symptoms increased from not doing any interventions
Ellipsoid joints don't allow which motion?
Flatness of the ellipsoid surface doesn't allow spin - Ellipsoid shape (oval and flat) does not allow rotation - Just flexion/extension and abd/adduction - Ex. Radiocarpal- radial /ulnar deviation
Forward leaning moves the center of gravity projection forward or backward?
Forward leaning moves the center of gravity projection forward. A, It remains inside the base of support when the casters point forward. B, It moves outside the base of support when the casters point to the rear. C, This causes the chair to fall forward.
"_______________________, where skin is pulled sideways over a bone when moving, is a particular risk for developing pressure ulcers" Folding Pinch Friction Compression
Friction
Cross-Sectional Area of fusiform muscle
Fusiform muscle: - Physiologic cross section (PCS) area is 'simple' because all fibers run parallel - PCS (red)= ACS (orange) Basically with fusiform muscles, have one line ID with cutting muscle at largest point (anatomic cross section) Physiologic cross section is perpendicular to muscle fibers Yellow- anatomic cross section --here, ACS = PCS
GH/Arm abducted 90, elbow flexed 90 Posterior deltoid--concentric action, plane, and axis
GH- horizontal abduction Transverse Longitudinal axis
My article findings
Gross mechanical efficiency was increased with high stimulation with the same energy expenditure for all test conditions
What do you call the force of the ground on your foot?
Ground reaction force OR the "normal force" = the force of the ground on your foot
Osteoarthritis Lets go back to our arthrokinematics. If an ellipsoid joint like the metacarpal phalangeal joints of the fingers develops increased bone mass/ bone spurs, what happens? Why is this important?
If an ellipsoid joint like the MP joint, if it has extra force around it, Person pounds ice with hammer every day Let's say impact of force goes to joints of hand - So body starts throwing more bone around the MP joint - So this restricts its movement - Don't know exactly where a bone spur shows up - But if find an extra bone around MP joint, may have arthritis- may have limited add/abduction of fingers and less ROM
***** AS WITH THE HUMAN BODY, COG CAN CHANGE WITH MOVEMENT • WE CAN DETERMINE THE CENTER OF ANY PART OF THE BODY (APPLY MECHANISTIC THEORY-LOOKING AT COMPONENTS)
If you find separate COG of segments of body and add them together, generally able to find entire body's COG COG of human body changes with movement
Force-Velocity Curve In isometric- get muscle at midlength and how many cross bridges?
In isometric- get muscle at midlength and maximum number of cross bridges exist **** No speed b/c no movement here so greater force than any speed of shortening
Areas of Practice --Ergonomics O Industrial settings O Office buildings (usually larger companies) O Consulting companies O Outpatient clinics O Setting in which therapists work sometimes determines how "client centered" their work can be ("client" could be the business itself or the worker)
Industrial settings- like going to the job site - Kohler and Birds Eye Foods - Kohler has lots of plants within the same company - Each setting comes with a different set of problems - Office buildings- big companies usually have an ergonomic consultant - Design of tools matters (Ex. Fiskars company engineers) - We do have valuable insight into the design of a shovel or how do we modify a wheelchair to improve one's seating stability
Skeletal § Voluntary § Between bones § Innervated by???
Innervated by somatic nervous system - Skeletal Voluntary AKA VOLITIONAL- - need to put thought into for movement - Ex. Tremor is non-volitional muscle contraction
Musculoskeletal levers characteristics
Insertions of muscle close to joint axis results in SHORT internal moment arms Distal parts travel greater distances at faster speeds --Distal parts (the extremities; hands and feet) travel greater distances at faster speeds (favors locomotion and manipulation) Muscles can shorten only a limited distance --limited excursion capability (means shortening for a muscle)
isometric contraction
Isometric contraction, in which a muscle develops tension but does not shorten. This occurs at the beginning of any muscle contraction but is prolonged in actions such as lifting heavy weights
Areas of Interest for Ergonomics Team FORWARD head is one of biggest problems in everyone - try to get closer to see it - get closer with head but not whole body
Lead with your heart not your head - Big for people with bad posture - Head moves back and shoulder comes back and back is in better alignment - **Don't worry about signal detection theory - Sometimes a simple change but often takes trial and error
Areas of Interest for Ergonomics Team Person-machine communication, workstation design, vibration, noise, temperature, illumination, training, inspection and maintenance, error and reliability, signal detection theory, visual displays, legal aspects of product liability, and advanced statistical research in these and other areas
Look at way person interacts with machine, workplace design (more physical design, how much reaching, awkward posture), stop person if putting self in danger Other risk factors like - Vibration (one of biggest risk factor for UE nerve, and joint injuries b/c body doesn't do well with vibrations) - want to limit amount of vibrations exposed to - (ex. With arthritic patients like grinding together joint surfaces really fast) - Using one hand or two - Tools they are using - Illumination - lighting in workplace for preventing slips, trips, and falls- decreasing risk of injury of walking into objects - eye strain- is a big one - FORWARD head is one of biggest problems in everyone - try to get closer to see it - get closer with head but not whole body - Lead with your heart not your head - Big for people with bad posture - Head moves back and shoulder comes back and back is in better alignment - Visual displays- could be signage or digital displays like computers - People squinting- may need vision checked - Try to find root of problem then work from there - **Don't worry about signal detection theory - Sometimes a simple change but often takes trial and error
mechanical advantage formula
MA = IMA / EMA
Occupational Safety and Health Act (OSHA) OSHA- sets standards in workplace to reduce injury
Major accidents at work OSHA goes there to try and reduce injuries (ex. More plexiglass barriers or gate around machines, lock out tag out- where you have to put a lock on a power button of a machine before leaving) Planning safety around what job is Most of the time it is simple stuff
for testing muscle strength in a SINGLE maximal voluntary contraction (MVC)--what is this called?
Manual muscle testing (MMT):a 6 point scale of 0-5 for testing muscle strength in a SINGLE maximal voluntary contraction (MVC) - MMT want to test in a SINGLE maximal voluntary contraction - But fatigue becomes an issue
Mary's transitional base of support is too far forward. When she moves to stand, she must travel forward more than is possible. Mary finds that with too little momentum what happens??
Mary finds that with too little momentum, her center of gravity projects behind the transitional base.
Cross-Sectional Area
Maximal force potential of muscle is proportional to the sum of the cross- sectional area of all it's fibers. (thicker muscle= greater force generation)
-To calculate the Moment--what is the equation?? ***Really important to remember!
Moment AKA Torque --To calculate the Moment (TORQUE) = force X distance (moment arm)****** really important to remember - -Moment= force X distance (moment arm) - -If the force is the same (ex. Both weight ten pounds) then increased distance determines the winner -If the force is not the same, have to shift this around
Moment arm of muscle force of biceps brachii increases or decreases from r1 to r2 during extension in elbow joint?
Moment arm of muscle force of biceps brachii decreases from r1 to r2 during extension in elbow joint - Elbow joint axis of rotation = white dot - Insertion of biceps brachii = black dot at 90°and blue dot at 120° - Arrows mark forces by which biceps brachii insertion acts on the forearm Moment arm= b/c white and black dot (IMA) - biceps pulling on the elbow So when the biceps goes into extension, insertion of the biceps is now moved and IMA shortens Longer moment arm at 90 degrees, shortens at 120 degrees Moment arms want to think of gravity -White = axis, insertion of biceps= black - -When extend elbow, white and blue horizontal line b/w the two -is SMALLER - -Only concerned with perpendicular length
Moment arms= perpendicular from what to what?
Moment arms= perpendicular from the axis to the line of force
Force-Velocity Curve Concentric:
Muscle contracts at maximum velocity with low/negligible load § As load increases, maximal contraction velocity of muscle decreases § Reduced force-generating capacity at higher velocities of contraction is due to inherent limitation in speed of attachment and reattachment of cross-bridges
Force-Velocity Curve Eccentric
Muscle force is directly proportional to velocity of muscle lengthening - as load increases, maximal contraction velocity of muscle increases Muscles produce greater force during eccentric activation than during isometric or any velocity of concentric activation
Myosin wants to touch actin so when Ca+ comes in , myosin can now get closer to the actin b/c Ca+ binds to what to change its shape?
Myosin wants to touch actin so when Ca+ comes in , myosin can now get closer to the actin b/c Ca+ binds to troponin and it changes shape - Basically body guard is distracted which allows myosin to grab onto ATP molecule, and changes its shape (b/c when binds to stuff, changes shape) - Myosin onto a little energy - hydrolysis of ATP _ sticks itself down with ATP which switches to ADP and Pi - creates energy
Recall Newton's Laws Newton's 2nd law:
NET FORCE EQUALS MASS TIMES ACCELERATION (F= MA) • NET FORCE = THE SUM OF ALL THE EXTERNAL FORCES ACTING ON THE OBJECT • MASS MUST REMAIN CONSTANT 2nd= F=ma- so net force= mass times acceleration
What is Ergonomics?
O Designing environments and products according to the physical, cognitive, and psychological characteristics of humans to prevent injury O Physical: visual, auditory, tactile, strength, anthropometric O Cognitive: learning, information processing, retention O Psychological: cultural influences, behavior, background ***ALSO PSYCHOSOCIAL- not what many ergonomic professionals look at - But v. important b/c includes people you are working with - More likely to go to job you hate if like people there
Ergonomics Research Example: Intra-discal pressure
O Pressure on spinal discs varies with position and activity, and because of this it is important to change positions frequently (no one position is best) O Standing position results in the highest intra-discal pressure O Position changes also support disc health Pressure on spine- will get more into this later on Valuable to point out that no one position is ever perfect no matter if you have perfect posture or strong core - Supposed to get up and walk around if sitting - Supposed to shift position when standing all day - Supposed to roll someone in bed every 2 hours - So should be moving positions - Sit-to-stand work place supports this - Movement improves lubrication of joints, blood flow, and flexibility - Contractures happen more often in fixed positions
Goals of Job Analysis
O Prevent musculoskeletal injuries O Promote safety and wellness O Decrease financial costs associated with lost work time, medical treatment and retraining O Ergonomics workplace analysis may include task analysis, videotaping, measurement and analysis of equipment and workstation, and workspace analysis
Ergonomics as applied to different performance areas ****Products and environments should match the people who use them
O Self-care: ergonomically designed toothbrushes and spigots O Sports: bicycles and snow skis are designed differently for men and women O Health care: patient lifts and education programs designed to minimize worker injury ---Basically everything you can take and analyze in day to day life and think of how to make it better If tool is uncomfortable- usually a prompt to explore it further Bicycles= v. biomechanically design and should be adjusted to fit the person Just like any tool should be designed to fit you specifically Really supposed to think of skis fit for you specifically
Areas of Practice --Ergonomics O Industrial settings O Office buildings (usually larger companies) O Consulting companies O Outpatient clinics
O Setting in which therapists work sometimes determines how "client centered" their work can be ("client" could be the business itself or the worker)
The Need for Ergonomics Research O Cost-benefit analysis is needed before third party payers are willing to implement ergonomic changes
O This research will help make workplaces and other settings safer and more efficient for the people who use them O Example: Dr. Garg & Dr. Kappellusch's research on Canvas - We need to be able to sell this to employers Doing an analysis of cost-benefit to prove that what you recommend will result in a gain for company after a certain amount of time Lifting and back pain in nurses- amount of money to get lifts for hospital rooms sounds insane but break down how many injuries you have and how much it costs on an annual basis ---Justifying how you are doing things and efficiency is really what it's all about - justifying solutions
Ergonomics Background for Occupational Therapists
O We are well educated in the procedures of problem identification, interviewing, observation, and record review O We have considerable knowledge in activity analysis, environmental adaptation techniques, and understanding human body function O Occupational therapists should seek additional training to work in this preventative field Generally take good notes and good at problem ID
Compression
Often mistakenly referred to as pressure is the special case of stress in which opposing loads push toward one another along the same line of application Compressive stress= distinguished by the perpendicular angle of application of the load - Usually results in a squeezing type of force Straps can be sources of compressive stress along with slings and loops
Mary's transitional base of support is too close to the wheelchair. Once she stands, she has difficulty preventing what from happening?
Once she stands, she has difficulty preventing her center of gravity from projecting in front of her transitional base of support.
Formal Analysis Tools in ergonomics
One example is: The Strain Index was proposed by Moore and Garg as a means to assess jobs for risk of work-related musculoskeletal disorders (WRMSDs) of the distal upper extremities (hand, wrist, elbow). O Other formal evaluation tools exist and should be considered on a case by case basis O A GLORIFIED activity analysis (and you remember how detail-oriented that was!) Strain index available online - Give each task a number based on how repetitive and forceful it is - Used to assess work-related musculoskeletal risk of UE - WISHA looks at more broad various parts of body - For wrist, hand, and elbow = more Strain index
Skeletal Muscle Structure Fusiform
Parallel fibers and fascicles (bundle of skeletal muscle fibers § High speed contraction and force production § ACS= PCS § Sartorius, Biceps Brachii, Brachialis Fusiform- From O to I - all fibers line up next to it - Parallel fibers - Anatomic cross section is SAME as physiologic cross section
Fusiform- what orientation of fibers are these? ACS vs. PCS?
Parallel fibers- fusiform - PCS= ACS
Active vs. Passive Tension Importance of muscle origin and insertion in using this rationale Need to consider O & I of muscle b/c this is how we determine muscle length - *****Especially important when muscles cross multiple joints
Passive tension- Non-contractile proteins- titin - creates spring-like resistance § Actin and Myosin are active (contractile) proteins § Non-contractile (structural or passive) elements: - Structural proteins live among the muscle fibers with actin and myosin - Extracellular connective tissues like collagen and elastin - Generate passive tension when stretched: §Spring-like resistance (or stiffness) § Does not depend on active contraction (like Hoover's quad stretch) § Generative passive tension= Important at very long lengths where muscle fibers lose active force-generating capability - Therefore, when cross-bridges are ineffective, muscle relies on passive tension to perform the action
Factors in Job Analysis O Muscular work O Control of movements O Efficiency O Body mechanics and force factors O Design of workstations O Heavy work & handling loads O Fatigue O Occupational stress & mental activity O Night work and shift work O Vision, noise & vibration, lighting O Psychosocial factors
Politics are everywhere that you never expected - ex. Working in a factory need to be very careful what you say to a manager - Want them to hear how you can save them money - Most companies want to refute injury claims - (ex. Pre-employment physicals) - some are simple but others are hired to show people that they came in with all of these problems and cannot blame it on the job - List of things to consider - can fix one of these things and may cause problem in another part - So how do you make the best compromise- what can we do to make sure that If we adjust this for this employee, how do we know it won't cause an issue for another employee - Ex. Drag a cart full of 8 cartons of chemicals instead of carrying them each time- take away arm strength but bring in loud noises and causes lots of vibrations into the arm - Understand you can solve something but may have another problem to deal with
Ergonomics Valuable to point out that no one position is ever perfect no matter if you have perfect posture or strong core
Pressure on spinal discs varies with position and activity, and because of this it is important to change positions frequently (no one position is best) - Supposed to get up and walk around if sitting - Supposed to shift position when standing all day - Supposed to roll someone in bed every 2 hours - So should be moving positions - Sit-to-stand work place supports this - Movement improves lubrication of joints, blood flow, and flexibility - Contractures happen more often in fixed positions **O Standing position results in the highest intra-discal pressure
Documenting progress hand therapy treatment shift from biomechanical to occupational adaptation model
Purpose/findings: show conjunction of biomechanical approach w/occupational approach to improve progression in treatment
Age and height affect mechanics affect sit to stand transfers Findings of raised height seat??
Raised seat height reduced angular velocity and displacement - reducing biomechanical demands for the hip and the knee
Plane joint
Relatively flat surfaces - Rubbing hands together side by side Rotation and sliding (translation) (ex. Intercarpal joints)
Rotary motion vs. linear motion
Rotary motion moves through same angle in same time -Torque -How most of our body works Motion caused by muscle contraction Rotary motion doesn't have to travel as far= vs. linear motion, the distal segment that needs to travel farther (like runners around a track) Farther from center of rotation, the faster it is - Like when to runners run around the track - the outside guy can finish the same as inside one but has to travel farther and faster
Sarcomere: distance b/w? and comprises what?
Sarcomere: Distance between Z-lines Comprises myofilaments - Thick= myosin - Thin= actin - Crossbridge: When thick and thin attach Contraction - Actin and Myosin want to bind - Binding= Contraction - Sliding filament theory: Z lines move toward each other, sarcomere shortens
Scalar Quantities
Scalar quantity is defined by its magnitude and has no direction Examples: § Space: Length, area, volume § Time § Speed § Mass
Difference Between Scalars and Vectors
Scalars and vectors are different. Both have magnitude, but vectors have magnitude and direction. --Scalar quantity= magnitude of a load ---Vector = force to be lifted or slid across the surface § Example: shoulder abduction of 180 Degrees § A scalar quantity describes an arc of shoulder motion of 180 degrees (range of motion) § A vector quantity describes this as shoulder joint abduction - Magnitude: starting at neutral (0) and ending at 180 degrees - Direction: in the coronal plane away from midline
Second class levers- rules
Second class levers Axis of rotation is on one end Both load and effort are on SAME side of fulcrum (ELF) ****Force act in different directions IMA (effort you apply on handles of a wheelbarrow) = LONGER than EMA (weight of wheelbarrow) Fulcrum= wheel of wheelbarrow WE always have the mechanical advantage here b/c our IMA is ALWAYS longer then the load's EMA Can determine how much weight we can handle if you knew how much force you could exert on the lever -Use this same equation -Torque= distance X force
Muscle Physiology Intrafusal and Extrafusal muscle Fibers
Sensory and motor respectively - Intrafusal muscle fibers: Proprioception sensors- detect changes in length and rate of change in length of a muscle - serve as specialized sensory organs (proprioceptors) that detect the amount and rate of change in length of a muscle - Innervated by Gamma Motor Neurons (y-MN) - Extrafusal muscle fibers: generate tension by contracting, generating skeletal movement - Extrafusal- tell muscles to move- open voltage-gates - innervated by alpha motor neurons Golgi Tendon Orgon (GTO) - Proprioception sensor - Senses change in muscle tension (A>P) Golgi tendon organ - At musculotendinous junction - senses change in muscle tension
Example: if a workstation is well designed, the worker should not have to hold his/her neck in an awkward posture to use a visual display terminal, and therefore should not experience neck and shoulder discomfort (DUE TO BIOMECHANICAL FACTORS) ---why due to biomechanical factors??
Should not have NO PAIN AT ALL - Maybe have to work on psychosocial aspect of it like stress management b/c stress can lead directly to pain
When considering the length-tension relationship for sarcomere function, which position would be most effective for lifting a bucket with the Bicep Brachii muscle? Shoulder neutral to slight extension, elbow flexed to 90 degrees in neutral forearm rotation Shoulder extended, elbow maximally flexed in supination Shoulder flexed, elbow flexed, forearm supinated Shoulder flexed, elbow extended and pronated
Shoulder neutral to slight extension, elbow flexed to 90 degrees in neutral forearm rotation
Joint type-Plane Primary Angular motions Mechanical analogy Anatomic examples
Sliding (translation) or sliding + rotation Relatively flat surfaces Intercarpal
Muscle Types 3 different muscle types
Smooth § Involuntary § In lining of visceral organs § Innervated by autonomic nervous system - (in kidneys and other organs) Cardiac § Involuntary § In heart § Innervated by autonomic nervous system - (Striated) § Skeletal § Voluntary § Between bones § Innervated by somatic nervous system Skeletal Voluntary AKA VOLITIONAL
Transfers When talking about transfers, one of the best things to do to take pressure of OT is to have pt do as much work as possible --what do you want the pt to do?
So have PT scoot forward to edge of their chair - b/c need to shift their COG over their base of support Have to get them comfortable with the fact that there is a reduced risk of falling when leaning forward and getting weight of butt off wheelchair
Joint type-Pivot Primary Angular motions Mechanical analogy Anatomic examples
Spinning of one segment around a single axis of rotation Door knob radio-ulnar Atlanto-axial
Generate passive tension when stretched
Spring-like resistance (or stiffness) § Does not depend on active contraction (like Hoover's quad stretch) § Generative passive tension= Important at very long lengths where muscle fibers lose active force-generating capability - Therefore, when cross-bridges are ineffective, muscle relies on passive tension to perform the action Non-contractile (structural or passive) elements: titin - creates spring-like resistance - Structural proteins live among the muscle fibers with actin and myosin - Extracellular connective tissues like collagen and elastin
A, Leaning and reaching forward to assist the client moves the OT practitioner's center of gravity projection too far forward relative to the base of support Standing close and bending at the knees keeps the OT practitioner's projection how??
Standing close and bending at the knees keeps the OT practitioner's projection more centralized in the base of support and decreases the risk of falling into the client.
Transfers Leaning and reaching forward to assist the client moves the OT practitioner's center of gravity projection too far forward relative to the base of support. 4. What is the reason given for lifting the patient using your knees?
Standing close and bending at the knees keeps the OT practitioner's projection more centralized in the base of support and decreases the risk of falling into the client. Transfers • BY BENDING YOUR KNEES YOU CAN KEEP THE WEIGHT OF YOUR UPPER BODY OVER YOUR BASE OF SUPPORT AND PULL THE PATIENT CLOSER TO YOUR CENTER OF GRAVITY.
Pre-employment Physicals and stop light approach
Stop-light approach- like caution/hazard on WISHA checklist - Will check flexiblilty in hamstrings- if contracted at certain level will give them a red light, if perfect flexibility will give them a green - 3-4 hour session to evaluate what your risk factors are - Good for ID if you are fit for the job Good for employer too b/c tells you what injuries you came in with on the job
CANNOT STRESS ENOUGH- Stress at workplace often leads to aches and pains and problems****
Stressed out increases pain, unreasonable workload can very well increase pain
How does the concave-convex rule apply to open and closed chain movements? (write-pair-share)
Switching from open to closed chain movement would switch if the concave or convex member is moving Ex. Tibiofemoral joint- Closed chain- distal is fixed - Would switch the convex being on concave - So arthrokinematics and osteokinematics would be going OPPOSITE instead of in the same direction like - But when its open, the arthrokinematics and osteokinematics of concave tibia and convex femur would move in the SAME direction would be going OPPOSITE instead of in the same direction - When kicking, going from flexion to extension - Concave member is moving in kicking ON the convex- SAME direction as osteokinematics - When sitting or standing in a closed chain movement, the moving member is convex femur - So the convex member is moving ON the concave- the OPPOSITE direction as osteokinematics
What is the protein associated with elastic tension in a muscle?
TITIN - protein associated with elastic tension in a muscle
According to the sliding filament theory, contraction of a sarcomere is the result of actin filaments sliding past myosin filaments True False
TRUE!
Eccentric activations produce greater force per unit of muscle ---True or False?
TRUE!!
T/F- The force produced by pennate muscles is greater than the force produced by parallel muscles.
TRUE!! - Since pennate fibers insert at an angle, the anatomical cross-sectional area cannot be used as in parallel fibered muscles. Instead, the physiological cross-sectional area (PCSA) must be used for pennate muscles. - Diagonal orientation of the fibers maximizes the muscle's force potential - Many more muscle fibers fit into the muscle compared with a similar size fusiform muscle - But b/c the muscle fibers are oriented obliquely, the actual range of motion, or excursion of the muscle is limited
T/F - Muscles produce greater force during eccentric activation than during isometric or any velocity of concentric activation
TRUE!! Reason is not well understood, but in part: - Greater force produced during cross-bridge detachment (think Velcro) - Rapid reattachment of cross-bridges - Passive tension produced by stretched part of muscle The faster you try to pull apart muscle, the more it resists (due to connective tissues in the muscles and tendons
T/F- - A muscle produces greater force isometrically than at any speed of shortening
TRUE!! § When contraction velocity is 0 (isometric) maximum number of cross bridges exist
Passive-length tension curve
Tension- same thing as force of contraction, or just FORCE b/c in passive there is no actual contraction In passive, can get a lot of slack in muscle, so muscle is close together but not contracting So once length increases passively, muscle gets longer and can go just slightly more before it breaks - Titin is your passive extensibility- keeps myosin structurally sound (in place where its supposed to be) b/c of their elastic nature, muscles ALSO produce force PASSIVELY - so muscles in this way, are similar to a rubber band - Like a rubber band a muscle generates greater internal elastic force when stretched - This elastic behavior= demonstrated by a muscle's passive length-tension curve
The line of force is perpendicular what and parallel to what?
The line of force is perpendicular to the axis of rotation and parallel to the plane of motion
The reclined position moves the center of gravity projection where?
The reclined position moves the center of gravity projection toward the back of the base of support. B, The quick start moves the base of support from under the center of gravity projection, and the chair falls backward.
Total length-tension curve for a typical muscle- at shortened lengths, resting, and stretched beyond its resting length?
Total length-tension curve for a typical muscle- at shortened lengths, all force is generated actively, at resting length, the optimal number of cross-bridges can form, resulting in the greatest force production. As the muscle fiber is stretched beyond its resting length, passive tension begins to contribute to the total force. The more the muscle is stretched beyond its resting length, passive tension accounts for MOST of the total force.
Leverage Trauma example: Dog leash wrapped around thumb when she sees a squirrel before you do. how long is the distance arm and how large is the force?
Trauma example: Dog leash wrapped around thumb when she sees a squirrel before you do. Close to the joint, but high force
If shift COG outside of body, system divided around that COG
Using a reacher makes it part of system, shifts COG can throw people off balance
Vector Quantities
Vector quantity can be described completely by its magnitude and direction Many of the quantities calculated in biomechanical analyses are vectors, so a thorough understanding of vectors is necessary (H & K, 1995). Examples: § Force § Displacement § Velocity: v = s/t § Acceleration: a = Δv/t = (v-u)/t = (final velocity-initial velocity)/t § Weight: W = mg, where g = gravity = 9.81 m/s2 - Units of Newtons [N] or pounds [lbs]
Vectors
Velocity, acceleration, and body weight are vector quantities - Body weight is a vector because it indicates a downward force on the ground due to the pull of gravity on body mass (F = W = mg). So, what would you call the force of the ground on your foot? - Ground reaction force
Condyloid joint
Very minimal rotation here - If look at MCP cannot actively produce rotation
High-Heeled Shoes and Stability
WEARING HIGH-HEELED SHOES VIOLATE ALL FACTORS OF STABILITY
When standing upright, COG lies where?
WHEN STANDING UPRIGHT, COG LIES IN THE ABDOMINAL CAVITY ~6 INCHES ABOVE THE PUBIC SYMPHYSIS (anterior to sacrum)
• Camber angle-advantages/disadvantages??
WIDENS THE BASE OF SUPPORT AND INCREASES THE CHAIR SIDE-TO-SIDE STABILITY • MAKES MANEUVERING THE CHAIR EASIER • LESS SHOULDER ABDUCTION AND SCAPULAR ELEVATION DURING PUSH PHASE • DISADVANTAGES? harder to navigate through tight spaces, harder to steer wheels at an angle - harder to push!!- but better for wheelchair sports
Principles of Ergonomics O When an appropriate ergonomic design is in use, the user should be unaware of???
When an appropriate ergonomic design is in use, the user should be unaware of environmental design deficiencies and be able to concentrate on the task at hand O Example: if a workstation is well designed, the worker should not have to hold his/her neck in an awkward posture to use a visual display terminal, and therefore should not experience neck and shoulder discomfort (DUE TO BIOMECHANICAL FACTORS) Important b/c if comfortable in task doing should be focused more on productivity (ex. If you're cold, that takes away from concentration- so cold environments are another risk factor in and of itself- decreases blood flow) Should have better field of vision to see what you are doing- should not experience neck discomfort Should not have NO PAIN AT ALL - Maybe have to work on psychosocial aspect of it like stress management b/c stress can lead directly to pain
§ When contraction velocity how many cross bridges exist?
When contraction velocity is 0 (isometric) maximum number of cross bridges exist - A muscle produces greater force isometrically than at any speed of shortening About the SPEED of contraction
Recommendations for healthy work stations
When standing to work a fully adjustable work table is best O For sitting to work, desktop height should be 740-780 mm; if too high, workers get pains in the neck and shoulders O Seat should be 270-330 mm below desktop; if too high or low back pain can occur O Varying position between standing and sitting is best What's more important is analyzing elbow and wrist position Wrist rest on keyboard and mouse CANNOT STRESS ENOUGH- Stress at workplace often leads to aches and pains and problems**** Stressed out increases pain, unreasonable workload can very well increase pain
- Crossbridge
When thick and thin attach
muscular force couple
When two or more muscles simultaneously produce forces in different linear directions, resulting in torques that act in the same rotary direction --****Another example of a muscle synergy - (ex. Occurs b/w two hands while turning a steering wheel- rotating the wheel to the R occurs by the action of the R hand pulling down and the left hand pulling up on the wheel) - Although they are producing forces in different linear directions, they cause a torque on the wheel in the SAME rotary direction
Workstation Analysis Will get practice with this in lab with worksheet
Will get practice with this in lab with worksheet 90 degrees at hip, knees, and elbow Want to be certain distance from screen 18-24 inches in front of you - should be looking at top 1/3 of screen Depending on adjustability of computer may need to stack books under monitors May need to put a stool under feet (ex. Desk one height may need to shorten chair) Tennis elbow and back problems - When reaching out too far or doing awkward wrist postures
Body position influences the entire body's COG.
With the arms raised and the trunk arched to the left, the COG moves upward and leftward.
Movement often changes the length of the muscle moment arm
With the elbow joint angle, what is the moment arm? As we bend our elbow (decrease the elbow joint angle), the moment arm decreases Motion caused by muscle contraction
"Bone is laid down in areas of high stress and reabsorbed in areas of low stress"--what law is this?
Wolff's Law Bone is a dynamic tissue that is constantly adapting to external forces So bone is not as stable as most people think - Has the potential to CHANGE - Not just here is your skeleton Explains bone spurs in osteoarthritic (OA) joints - This is why people with osteoarthritis get bone spurs- put down extra bone to protect skeleton Bone density decreases in people with paralysis or other non-use conditions, increasing the risk of fractures in people with spinal cord injury (SCI)
Psychosocial Factors O What does work mean to people? O Consider malingering and secondary gain
Work is often most important thing to people So if lose their job, often crushed and won't want to get out of bed So will be very sensitive to you telling them they are doing things wrong or concerned that their job will be taken away - create a whole dilemma and anxiety for person - But also think of malingering (people who don't want to work) - and will do anything to get hurt so get worker's comp - Will get a variety of perspectives on what work means to them - Malingering and secondary pain are a whole other side of this
Psychosocial Factors O What does work mean to people?
Work is often most important thing to people So if lose their job, often crushed and won't want to get out of bed So will be very sensitive to you telling them they are doing things wrong or concerned that their job will be taken away - create a whole dilemma and anxiety for person - But also think of malingering (people who don't want to work) - and will do anything to get hurt so get worker's comp - Will get a variety of perspectives on what work means to them - Malingering and secondary pain are a whole other side of this
Which is an important co-contraction when making a forceful grip? wrist extensors wrist flexors forearm pronators finger extensors
Wrist extensors
Are stress and pressure considered the same thing? Yes No
YES Pressure - weight with the added component of surface area (pressure and stress are considered the SAME THING) Stress - denotes the internal resistance generated as the ligament resists deformation, divided by its cross-sectional area
Transfers • BY BENDING YOUR KNEES YOU CAN DO WHAT?
YOU CAN KEEP THE WEIGHT OF YOUR UPPER BODY OVER YOUR BASE OF SUPPORT AND PULL THE PATIENT CLOSER TO YOUR CENTER OF GRAVITY. • LOWERING YOUR CENTER OF GRAVITY HEIGHT, INCREASES STABILITY.
What is a physical problem that results when armrests are positioned too high? elevating shoulders kyphosis hyperextension of neck all of the above
all of the above
What is a possible solution for posterior pelvic tilt in a wheelchair? check that the seat length is not too long pelvic belts anti-thrust seats all of the above
all of the above
What is the term used for the slight movement that is allowed within the joint that is passive and non-volitional? accessory movement arthrokinematics isometric activation close-packed
accessory movement
When a muscle is at rest- nothing is happening here b/c this system works to contract the muscle- so actin and myosin are NOT touching
actin and myosin are NOT touching when muscle is relaxed
What are the joint arthrokinematics of the proximal radial joint moving against the humerus with elbow flexion? anterior roll, anterior slide (same) posterior roll, posterior slide (same) medial roll, lateral slide (opposite) none of the answers
anterior roll, anterior slide (same)
What is one energy conservation strategy?
eliminating unnecessary tasks
Which of the following motions occurs around a medial-lateral axis of rotation? both knee flexion and shoulder extension shoulder extension knee flexion shoulder abduction
both knee flexion and shoulder extension
It's extremely important to consider ______________________ when deciding whether standup wheelchairs should be prescribed. the person's weight living on earth or moon center of gravity none of the above
center of gravity
2 types of cells in joint?
chondrocytes and fibroblast ---BOTH chondrocytes and fibroblasts are also responsible for maintenance and repair of tissue Both responsible for maintenance and repair- pull out inflammatory cells and bring good ones in generally Fibroblasts: stimulate collagen production, form a structural framework for tissues, important in wound healing - collagen is important to HEALING- help improve collagen formation - so fibroblasts will increase and collagen turns to articular cartilage and scar tissue - so good and bad Chondrocytes: cells of the cartilage (recall medical terminology)
Stable seating systems are created by balancing forces acting on a person. The forces to consider when choosing proper seating system include: only gravitational forces compression forces, shearing forces, and gravitational forces seating system forces and gravity only only seating system forces like a seat bel
compression forces, shearing forces, and gravitational forces
When considering active and passive tension relationships in muscle function, would it be easier or more challenging to flex the elbow with the shoulder extended? ---easier ---more challenging
easier -Principles of passive tension, the more a muscle is stretched the more passive tension is built up making it easier for the sarcomeres to shorten -Passive tension and active tension combine together - passive tension makes the larger tension more -GRAVITY also makes this easier!! -When shoulder is fully extended passive tension in biceps AND gravity push arm down- really making it easier
When considering only "the physical aspects of a person, the physical assessment should be conducted ___________" in the home, work, and transportation environment with the person, their caregiver, and their physical therapist only in the wheelchair they're interested in or have in a seated position, outside of a chair, and supine
in a seated position, outside of a chair, and supine
Areas of Interest for Ergonomics Team Areas of Interest Safety:
info regarding accident losses, Occupational Safety and Health Act (OSHA) standards, codes, and safety documents; designing, planning and production errors; hazards; pressure and electrical hazards, and other aspects of workplaces involving risk for injury (toxic materials, radiation, vibration and noise, etc) OSHA- sets standards in workplace to reduce injury Major accidents at work OSHA goes there to try and reduce injuries (ex. More plexiglass barriers or gate around machines, lock out tag out- where you have to put a lock on a power button of a machine before leaving) Planning safety around what job is Most of the time it is simple stuff
Sliding filament theory is what we apply to
is what we apply to length-tension relationship, connects to isometric, concentric, and eccentric Apply to synergies and co-contractions
"It is not always possible to increase strength. When strength (and/or endurance) cannot be increased because of pathology, _________________ may be implemented to prevent further dysfunction"
joint protection strategies
"stable posture results from a balance of competing forces, movement occurs when competing forces are what?
movement occurs when competing forces are UNBALANCED" - In order for knee to move, muscles must overcome competing forces (usually gravity)
If passive ROM is more than active range the problem is, If passive ROM is the SAME as active the problem is??
n If passive ROM is more than active range the problem is weakness: do strengthening of weak muscles (unless contraindicated) n If passive ROM is the same as active the problem is stiffness: do stretches and strengthening (unless contraindicated)
Penniform- what orientation of fibers are these? ACS vs. PCS?
oblique § Unipennate § Bipennate § Multipennate - PCS>ACS
Tensile
opposite in nature to compressive stress - The result of opposing loads pulling away from a surface along the same line of application - Referred to as tension and distraction results in stretching As is true with compression, tensile stress is greatest when the force is applied perpendicular to the surface
wheelbarrow technique of wheelchairs and points of contact??
performing the wheelchair technique reduces the base of support because there are 2 points of contact on the floor instead of 4 - so the base of support is very small with just the two front wheels on the ground, making it more likely a person would fall out of the chair
The shoulder adductor muscles are antagonists to: shoulder abductors shoulder flexors shoulder internal rotators shoulder extensors
shoulder abductors
"Manual wheelchairs have large wheels in the rear and small wheels in the front to enable the user to _______" none of the answers adjust the center of gravity stabilize the chair when resting on flat ground push the wheelchair in the most effective and efficient way
push the wheelchair in the most effective and efficient way
Which of the following is not considered normal arthrokinematics? rocking spinning sliding rolling
rocking
Basic unit of contraction of muscles
sarcomere- smallest unit in muscle 2 proteins really care about in sarcomere= actin and myosin Match made in heaven- think of it like a love story Different parts of muscle - Muscle fibers - Fascicles - w/n fascicles have muscle cells (myofibril) - This is where your sarcomeres live (w/n myofibrils) - Have sarcomere units living in this muscle cell area - Zig zags = Z discs - One small section= sarcomere
Which measurement is not required for seating assessment? seat to the elbow seat to the scapula seat to the top of shoulder seat to top of head
seat to the elbow
Active vs. Passive Tension (ex. Biceps cross shoulder and elbow and does supination) Full stretch of biceps=
shoulder extension, elbow extension and supination - Generate passive tension when stretched: §Spring-like resistance (or stiffness) § Does not depend on active contraction (like Hoover's quad stretch) § Generative passive tension= Important at very long lengths where muscle fibers lose active force-generating capability Therefore, when cross-bridges are ineffective, muscle rel
- When brain comes to anterior horn cell to muscle fiber, sensory fiber and muscle fiber actually talk to each!!!
so sensory fiber help determine what length is- you can feel this when you are stretching
As the muscle is progressively stretched, the tissue is slack during its initial shortened length until it reaches a critical length where it begins to generate what??
the tissue is slack during its initial shortened length until it reaches a critical length where it begins to generate tension. Beyond this critical length, the tension builds exponentially
6 synovial joints in the human body!!
these types of joints MOVE - don't really care about other ones like skull joints or pubic symphysis that don't move - Condyloid - Ball and socket- allows movement in all axes - flexion/extension, adduction/abduction, rotation and circumduction - at the hip and shoulder- hip has stability but limited ROM b/c of deeper socket, shallower socket in shoulder = more likely to dislocate - Saddle- similar to ellipsoid but rotation is limited b/c of structure - each bone has both a concave and convex surface- flex/extend, adduct/abduct, and circumduction and very slightly rotate - ex. CMC joint of the thumb - Hinge - allows movement in 1 axis - 1 df- allows a very stable movement - Plane- glide or rotate on one another - (ex. AC joint) - (when we elevate the shoulder, adjusts to keep scapula vertical) - Pivot -radial-ulnar joint- only rotates - pronation and supination - rotation of radius over ulna - distal ulna and radius= also a pivot joint allowing pronation and supination Added in video: Ellipsoid- 2 df - flexion/extension, adduction/abduction and circumduction combo of all others in a circular motion (radiocarpal joint= ellipsoid joint)
Accessory joint movement or joint play
what joint is able to do by some OUTSIDE force based on amount of space available in a joint depending on its position - slight, passive, nonvolitional movements allowed in most joints (also called joint play). Open and closed packed - (ex. When in flexed position with fingers, the joints are more congruent (CLOSED) this blocks you from abducting fingers)
passive insufficiency
when a 2 joint muscle is lengthened over both joints simultaneously When a muscle-tendon unit crosses more than one joint, it does not have the elastic capability to stretch across all of the joints
Gravity and the Development of Movement • LABYRINTHINE REFLEXES
your response to gravity and changes in movement - basically what you need to know for now - A VARIETY OF EYE, TRUNK, AND LIMB MOVEMENTS DUE TO STIMULATED HAIR CELLS IN THE LABYRINTH • LABYRINTH = VESTIBULAR SYSTEM OF THE INNER EAR • GRAVITY CAUSES MOVEMENT OF SMALL CRYSTALS (= OTOLITHS) DURING HEAD MOVEMENTS STIMULATES HAIR CELLS TO TRANSMIT INFO TO BRAIN ABOUT HEAD POSITION BARRIER - STRENGTHENING MUSCLES Will go more into depth with this in the sensory lecture into detail about vestibular system
§ Anatomic Cross-section (ACS) vs. Physiologic Cross-section (PCS):
§ Anatomic Cross-section (ACS): ACS = anatomical cross section)(standard cross section of a muscle) § Physiologic Cross-section (PCS):PCS (physiological cross section (perpendicular to muscle
MA- Example: revolving door
§ If you push a revolving door near the outer end it revolves fairly easily. § If move your point of force closer to the hinge, it requires more force to turn ****The increased distance (moment arm) creates a mechanical advantage
Mechanical Advantage aka leverage
§ Less force needed to cause motion when the force is exerted farther from the axis of rotation - This is also called leverage - Moment = Force x distance §Example: door §If you push a revolving door near the outer end it revolves fairly easily. §If move your point of force closer to the hinge, it requires more force to turn §The increased distance (moment arm) creates a mechanical advantage
Moment Arms § Moment arms are perpendicular to what ?
§ Moment arms are perpendicular to the line of force § The shortest distance from the line of force to the axis of rotation
Musculoskeletal Levers § Most musculoskeletal lever systems act as what kind?
§ Most musculoskeletal lever systems act as third class levers Therefore most muscles act at a mechanical disadvantage - § Most muscle insertions lie close to the joint axis § Results in short internal moment arms § Generally, muscles must generate greater forces (internal forces) than the resistance loads they encounter (external forces) §Distal parts (the extremities; hands and feet) travel greater distances at faster speeds (favors locomotion and manipulation) §Muscles can shorten only a limited distance - § they have limited excursion capability EXCURSION - AKA range of motion
Center of Gravity Projection • IN VECTOR TERMS, WE WOULD DRAW THIS CENTER OF GRAVITY PROJECTION HOW??
• IN VECTOR TERMS, WE WOULD DRAW THIS CENTER OF GRAVITY PROJECTION AS A DOWNWARD ARROW STARTING AT THE CENTER OF MASS. IT INDICATES THE GRAVITATIONAL PULL ON OUR BODY.
Cross-Sectional Area § Pennate muscles produce more force than fusiform muscles of similar volume
§ Pennate muscles produce more force than fusiform muscles of similar volume - By orienting fibers obliquely to central tendon, a pennate muscle can fit more fibers into a given area of muscle - This space-saving strategy provides pennate muscles with relatively large physiologic cross-sectional area = relatively large capability to generate high force So bipennate can fit more fibers in the same amount of space as fusiform!!
Wheelchair Wheels • CHANGING THE POSITION OF THE FRONT CASTORS AND REAR WHEELS CHANGES A WHEELCHAIR'S STABILITY
• A CHAIR MOVING FORWARD HAS A SHORTER BASE OF SUPPORT THAN A CHAIR MOVING BACKWARD - When castors are pointed backward, reduces base of support - If positioned forward, actually helps with stability - Person who might reach outside of base of support without warning, important to turn castors forward while waiting so they have more stability when waiting or doing activities
• AIR RESISTANCE (AKA: DRAG)
• A TYPE OF FRICTIONAL FORCE OPPOSING MOTION • ACTS IN OPPOSITE DIRECTION THAT THE OBJECT IS MOVING • ALL MOTIONS • Air resistance - INCREASES WITH INCREASED SURFACE AREA (DEMOS) • FALLING FROM SKY: APPLE (PAPER DEMO) • MOVING ALONG GROUND: CAR (HAND OUT CAR WINDOW "DEMO")
Rear-wheel camber and its effect on the width of the base of support??
• CAMBER IS THE ANGLE OF THE REAR WHEELS OF A WHEELCHAIR • THE HIGHER THE DEGREE OF CAMBER, THE MORE OF AN INCREASE IN WIDTH ACROSS THE BOTTOM
Wheelchair Wheels, Camber --what is camber?
• CAMBER IS THE ANGLE OF THE REAR WHEELS OF A WHEELCHAIR • THE HIGHER THE DEGREE OF CAMBER, THE MORE OF AN INCREASE IN WIDTH ACROSS THE BOTTOM
Factors in Stability KEY FACTORS THAT ALLOW US TO BE STABLE IN THE PRESENCE OF GRAVITY
• CENTER OF GRAVITY HEIGHT • BASE OF SUPPORT • CENTER OF GRAVITY PROJECTION • WEIGHT
The front casters swivel to point to the front when the chair stops backing up (A) and to the rear when it stops moving forward --what does the caster position influence??
• CHANGING THE POSITION OF THE FRONT CASTORS AND REAR WHEELS CHANGES A WHEELCHAIR'S STABILITY • A CHAIR MOVING FORWARD HAS A SHORTER BASE OF SUPPORT THAN A CHAIR MOVING BACKWARD
Center of Gravity • IN NON-UNIFORM OBJECTS, (SHAPE AND/OR MASS DISTRIBUTION) THE COG IS THE MEAN LOCATION OF ALL THE MASS IN A SYSTEM • IF OBJECT IS ACTED UPON BY AN UNBALANCED FORCE AT A POINT OTHER THAN COG, what happens??
• IF OBJECT IS ACTED UPON BY AN UNBALANCED FORCE AT A POINT OTHER THAN COG, IT WILL ROTATE ABOUT THE COG. • ACCELERATION OF THE COG IS G AT ALL POINTS OF THE TRAJECTORY (9.81m/s2)
• IF YOU ARE STANDING UP STRAIGHT, where is the COG projection located?
• IF YOU ARE STANDING UP STRAIGHT, IT IS LOCATED PRETTY CLOSE TO THE SPOT IN THE MIDDLE OF YOUR FOOT PRINTS ON THE GROUND (YOUR BASE OF SUPPORT) • IF YOU SHIFT YOUR WEIGHT TO TRY TO RELOCATE YOUR CENTER OF GRAVITY PROJECTION OUTSIDE OF YOUR BASE OF SUPPORT YOU ARE MORE LIKELY TO FALL! Gravity PROJECTION - If gravity projection falls outside of base of support- more likely to fall
Center of Gravity • IN NON-UNIFORM OBJECTS, (SHAPE AND/OR MASS DISTRIBUTION) is located where?
• IN NON-UNIFORM OBJECTS, (SHAPE AND/OR MASS DISTRIBUTION) THE COG IS THE MEAN LOCATION OF ALL THE MASS IN A SYSTEM versus COG = CENTER OF MASS (COM) IN UNIFORM GRAVITATIONAL FIELDS
Segmental Centers of Gravity SEGMENTAL ANALYSES
• IT IS USEFUL TO BREAK THE BODY INTO SEGMENTS • THIS MEANS WE CAN LOOK AT THE FOREARM, ARM OR LEG ALL BY ITSELF • USING DATA ALREADY REPORTED, WE CAN FIGURE OUT THE WEIGHT OF ANY SEGMENT IF WE KNOW THE PERSON'S TOTAL WEIGHT Break body into smaller pieces (segments) Then using data we already have, can figure the weight of a segment if know someone's whole body weight
Wheelchairs • WHEELCHAIRS ARE DESIGNED FOR STABILITY
• LARGE BASE OF SUPPORT • RELATIVELY LOW COG • SUBSTANTIAL WEIGHT • PROJECTION OF COG WELL WITHIN THE BASE OF SUPPORT
Center of Gravity Height --want a higher or lower COG?
• LOWER COG HEIGHT GIVES BODIES MORE STABILITY • (TODDLERS BEGIN TO WALK WITH PARTIALLY FLEXED KNEES AND HIPS) • COG CAN BE RAISED OR LOWERED BY YOUR POSITION!
Gravity and the Development of Movement STRETCH REFLEXES • EX: BABIES!
• MOVEMENT CAUSED BY GRAVITY IN ONE DIRECTION TYPICALLY LEADS TO MOVEMENT BY MUSCLE CONTRACTION IN OPPOSITE DIRECTION Stretch reflexes with babies tummy time is important to have neck extensors get stronger b/c these hold the head up when standing - Need to learn how to use muscles to fight against gravity
Wheelchairs • WHEN TIPPING A WHEELCHAIR UP (AS IN A WHEELIE OR TO PULL A PATIENT UP OR DOWN A CURB) THE HANDLES ARE PUSHED DOWN, CAUSING THE FRONT TO LIFT UP. • THE BETTER WAY TO TIP IS TO USE THE TILT BAR ON THE FRAME • 5. DOES THE CENTER OF GRAVITY PROJECTION MOVE ANTERIOR OR POSTERIOR?
• POSTERIOR
Reclining Wheelchairs • REDISTRIBUTION OF WHEELCHAIR MASS • PROJECTION OF COG--moves where???
• PROJECTION OF COG CLOSER TO THE REARWARD BORDER OF BASE OF SUPPORT - COG shifts backwards when pt reclines - b/c of friction, this makes them more likely to slide out b/c weight is scooting forward now - And could tip back
Center of Gravity Projection THE CENTER OF GRAVITY PROJECTION IS ALSO INDICATED BY A DOT ON A DRAWING OF THE BASE OF SUPPORT The COG projection will or will not generally move outside base of support if you are stable?
• THE CENTER OF GRAVITY PROJECTION WILL GENERALLY NOT MOVE OUTSIDE OF THE BASE OF SUPPORT IF YOU ARE STABLE
Gravity: Earth and Moon F= MG - b/c gravitational constant= an acceleration (G) - Weight of anything = mass X gravity - So can look like W= mg (same equation as F=ma or F=mg) - b/c gravity is an acceleration and weight is a force • ON EARTH, GRAVITY IS THE SAME EVERYWHERE, SO DIFFERENCES ARE DUE TO VARIATIONS IN MASS • ON THE MOON, GRAVITY IS THE SAME EVERYWHERE, SO WHATS THE DIFFERENCE BETWEEN EARTH AND MOON?
• THE GRAVITATIONAL FORCE IS DIFFERENT ON THE MOON! - Gravitational force is a different number that's all - Mass does not change - These equations show difference b/w gravitational force of the moon and Earth - So why we weigh less on the moon b/c gravitational force is less
Gravity and the development of Movement • THE PULL EXERTED BY THE EARTH ON ALL OBJECTS IS THE SAME, I.E., IT CAN BE REPRESENTED BY A CONSTANT VALUE what is this constant called?
• THIS CONSTANT IS CALLED THE GRAVITATIONAL CONSTANT, G • G = 9.81 M/S2 • IT IS ALSO TERMED AS THE ACCELERATION DUE TO GRAVITY
First Class Levers The following are always true of first class levels:
• The axis of rotation (fulcrum) is between the resistive force and the applied/effort force • Mechanical advantage can be =, >, or < 1 • Both forces act in the same direction § Musculoskeletal example: • Head on neck § Non-musculoskeletal: • Teeter totter, scissors
The axes of the three CARDINAL planes of motion intersect WHERE??
• axes intersect at the center of gravity (COG) • The COG is a point anterior to the second sacral vertebrae (S2)
