Applied Biomechanics
69. Provide several sporting examples of the SSC in use.
Bench press touch and go rep
Why is there a need to develop qualitative analysis procedures and standards?
Help guide the coaches eye towards key features of performance.
The movement analysis phase consists of what four stages? List these and explain them.
Determine the goal - deadlift Division of the goal - straight arms Determine mechanical factors - decrease moment arm from hips to bar (decreases torque) Determine critical features - full extension of elbow and shoulders over hands during set up
List several methods of observation giving an example for each.
Direct - eye, video, viewfinder, cortex recall Indirect - chipped grass (golf), foot prints, noise from bat, athlete feedback
Cinematography has largely been superseded by video. However, there still remain some advantages of using this method for motion analysis. List the advantages and disadvantages of cinematography over video.
Early Advantages over video: Clarity of image - (more co-ordinate points when digitizing) Higher shutter speeds: - 1/48000 sec Freeze bullet Freeze golf ball More frames/sec: easily up to 500 per sec Disadvantage over video: Lack of immediacy in result Manual digitising Expensive Poor time scale
109. List the advantages and disadvantages of digital video over analogue video.
Early Disadvantage over cinematography: Decreased clarity of image (resolution) Inflexible adaptations Interchangeable lenses (distortion) Gen-locking for 3D analysis Often have non-manual settings
Why is the science of anthropometry an important component of ergonomics?
Individuals have unique body proportions and segment ratios > specific comfort and injury free zones
There are six main contributory factors that injury occurrence and type in sport / exercise / work depend upon. List, explain and provide examples for each of these six factors.
Load characteristics Type (tension, compression, shearing, etc) Magnitude Load rate Frequency of load repetition Characteristics of loaded tissues Material properties of bones & soft tissues Structural properties of bones, joints & soft tissue Genetic factors Innate musculoskeletal deformities E.g. Flat feet, leg length differences Age, sex Fitness or training status Lack of flexibility or joint laxity Muscle strength imbalances Incorrect body weight Excessive training load for fitness state Over-training, fatigue Technique Poor technique causing excessive loads Illegal technique Equipment and surfaces Human surface interface Human and equipment interface
85. List and explain several factors that influence flexibility.
Joint structure Soft tissue Ligaments Actual physical length of the antagonistic mms & the level of neurological innervations as mm is stretch
70. Define Muscular strength.
'the peak force or torque developed during a maximal voluntary contraction'
59. What is a motor unit and what do they control?
1 efferent nerve and all the muscle fibres it controls (includes synaptic junction, endplate etc.)
100. List examples of kinematic measurement methods other than visual measurement techniques.
Goniometers Accelerometers
61. Explain how muscle force production is controlled or graded.
Graded force production comes by either increasing the rate of stimulation or by the recruitment of additional motor units.
Several guideline rules are suggested when developing a mechanical model. List and explain these rules.
1. Mechanical quantities - force, torque (non-colloquial) 2. Each factor must be determined by that below it - bar close to body > scapula retracted (effect and cause) 3. Only direct effects should be included 4. Stop dividing when mechanical factors can't be broken up 5. Relationship between boxes on same line is not shown.
Explain the process for identifying errors.
1. identify and compare (performed vs desired outcome) 2. classify as primary or secondary errors (primary causes secondary) 3. prioritize - aim for largest improvement with time available, one or two improvements at a time, start with the most primary errors
119. List and explain several sources of error when digitising and how these errors might be minimised.
Grain / pixels Marker shift Segmental data assumptions Motion outside plane perpendicular to camera axis (2D) Motion outside calibration volume Data filtering/smoothing technique Calculation of derived quantities Timing calibration
42. What does "lifting limits in manual handling" mean?
25kg (NIOSH suggestion?) limits for what should be lifted alone, with help or with tool
53. Which muscle fiber type reaches peak tension the fastest and why?
2b (FG) greater myosin ATPase
Briefly explain the difference between Optoelectric, Automatic and Real-time automatic motion analysis systems.
Optoelectric systems: Active markers (infrared lights) Passive markers (reflective markers): Infra -red video-based systems Automatic systems: Automatic marker tracking Automatic prediction and marker search Real-time Automatic systems: Use either Video or IR-sensitive cameras Can generate capture and reconstructed output in real-time (very slight delay) Systems of the future No marker Modeling + image recognition
94. List several biomechanical measures that can be determined using force platforms.
Passive/active loading Different patterns - rear-foot, mid-foot or fore-foot strikers Different surfaces, different running shoes. 8.3 x BW in long jump take-off 9.1 BW for back foot strike in javelin Forces during landings Up to 12.3 BW for front foot strike in fast bowlers Swimming starts and turns Rowing
Several problems and sources of error in 2D recording were presented to you in class. List and explain each of these issues
Perspective error Parallax error Lens distortions Location of landmarks Identification of anatomical features Measurement estimates based on skin markers (move) Joint obstruction from view Accuracy of sampling rate (time consistency) Image quality Sampling rate, shutter speed, aperture Lighting Background Calibration
Explain the difference between Piezoelectric and Piezoresistive transducers and outline the advantages and disadvantages of each.
Piezoelectric force systems work on the principle of development of an electrical charge on deformation of quartz crystals when force is applied. Drift can occur with repeated use Well suited for sport movements (rapidly changing forces) Less affected by temperature than piezoresistive systems Generally more difficult to install Possess a widely adjustable range Piezoresistive (Strain gauge) force measurement systems are made from materials whose resistance changes when deformed. Easier to install and less expensive than piezoelectric force platforms Prone to shift with temperature.
118. What is digitising?
Process of converting film/video images into computer images with known co-ordinate geometry
Pre-observation involves what two phases?
Movement Analysis Model/ Observation Planning
62. Explain the Motor Unit Size Principle.
This principle states that the size of newly recruited motor units increases with the tension level at the time of recruitment. Smallest unit is recruited first and largest last. Allows tension to be achieved in graded steps.
What critical features must be considered when designing an observation plan?
Those which DIRECTLY influence the goal
134. List and explain the 2 main classes of processing raw EMG signals.
Time domain - mean value, variation over time Frequency domain - measure frequencies and peak power
What is the purpose of the diagnosis phase?
To identify source of fault and determine solution which is tailored to athlete's individual need.
The prevention and reduction of risk stage involves the application of knowledge obtained from the earlier stages and can result in what? Provide at least one example for each.
Rule changes - AFL ball up jumpers within ring Equipment modification - cricket helmet Technique modification - landing retraining Physiological adaptation - strengthen rotator cuff
Describe the correct placement of surface electrodes (including site preparation) for recording a clean EMG signal.
Shaving area, removing dead skin cells and skin oils with alcohol and increasing local skin blood flow Use conducting gel away from tendons away from nerve connection 2-5cm apart parallel to muscle fibre ground electrode on bony landmark
31. List and provide an example for each of the 5 types of stress that can be applied to the body.
Shear, compression, tension, bending, torsional
82. List and explain 4 principles of resistance training.
Specificity - only train relevant muscles/movements, tailor to athlete experience, consider range of motion Overload / Intensity - progressive overload, measure at % of 1RM, work above "normal" levels Variation - train variably to avoid imbalances and develop whole limb stability, Recovery / Rest - removal of metabolic products, time for adaptions to develop
24. Why is it incorrect to instruct a worker to maintain a "straight back"?
Spines natural S shape provides strength to posture
26. Explain the "pros" and "cons" of standing and sitting posture in the workplace.
Standing: Exert greater force, Lower lumbar pressure, Greater reach, Vibration dampening Sitting: Relaxing, Convenient
77. What does the slope of force-time curve indicate and what is the significance of this measure?
a steeper slope indicates a quicker time to peak measured contraction and therefore more power is produced.
Reductions in workplace back injuries can be achieved by: a) risk identification; b) risk assessment & c) risk control. Explain each of these phases.
a) analyse hospital data, consult employees, direct observation b) analyse workplace arrangement, task and efficiency c) redesign, train, policy, equipment
127. An electromyography signal is the composite electrical sum of what?
all of the active motor units
147. Describe how uphill and downhill running can increase the risk of injury.
alter kinematics - work unpractised structures alter rate and magnitude of loading
In what form is the signal collected using force transducers and what must be done to it to allow a numerical value of force to be calculated?
analogue to digital, calibration is required
107. What is the difference between analogue video (VHS & SVHS) and digital video?
analogue video composes an image of coloured dots and lines, this can limit clarity especially during motion
140. Describe the process involved in stage 1 - Description of incidence and types of injury.
analyse statistics of injury as well as visual analysation of movements in question
Explain the difference between the anatomical and physiological cross-sectional area of muscle tissue
anatomical = perpendicular to line of force across muscle belly physiological = perpendicular to arrangement of muscle fibre direction
73. Define Muscle power.
The amount of work a muscle can produce per second of contraction.
43. Quantified lifting injury risk increases when?
bulky object, heavy, from floor, frequent, poor grips
132. Explain the use of amplifiers in EMG recording.
clean signal with filtering
45. Name the 2 major components of muscle tissue.
contractile element/ series elastic component
Explain the statement: Accurate co-ordinate reconstruction can only be guaranteed within the calibration volume.
data which would be measured outside calibrated range are not recorded or assumed
128. Why does an EMG signal have both positive and negative components?
depolarisation and repolarisation of muscles
102. Define "depth of field" and "aperture" and explain the relationship between them.
depth of field = distance between in focus near and far objects. aperture = amount of light a leans can transmit smaller aperture = greater DOF
Ergonomic improvement to work systems can be achieved by doing what?
design interface to be more compatible with task & user > safer environment, alter for individual, accomodate psychological/ social needs
135. Discuss the relationship between EMG and biomechanical variables.
detect timing of muscles and their influence on kinematics (sequencing) determine ROM that requires greater effort time to peak contraction differentiating fatigue (muscular/neural)
How can the point of attachment of a tendon to the bone affect the mechanical force of muscle contraction?
determines lever length and therefore torque output during contraction
66. Define the term "stretch shortening cycle (SSC)".
eccentric loading of the muscle which results in a storage of energy in the elastic components of the muscle (i.e. mm fibers and sheath) followed by a concentric contraction. Magnitude of force of the concentric phase is the summation of the stored elastic energy and the force produced by the concentric contraction of the muscle.
131. List several factors that may influence the quality of EMG signal.
electrode position skin/adiposity (100 micrometres from the muscle fibre - about 80% of the signal strength is lost) blood flow
What is ergonomics?
The study of the relationship between humans and machines and the efficiency of this
28. List several myths of ergonomic seating.
everything should be adjustable, comfortable at first sit/ glance
103. Explain the relationship between shutter speed, aperture and exposure.
exposure = amount of light that hits film, shutter speed will determine how long exposure lasts and aperture will limit light
29. Name at least 5 key features of ergonomic chair design.
feet on ground, neutral spine (S shape/ ears, shoulders, hips in line), not slouching over desk, lumbar support, comfort
Explain in detail the muscle "force-velocity relationship" and provide an example how this relationship can advantage or disadvantage a performer.
force is decreased throughout a concentric contraction but increased throughout an eccentric contraction. isometric contractions apply more force than eccentric, therefore to accomodate the load on arms during a handstand, elbows should be locked straight before inverting as opposed to performing a concentric contraction (handstand pushup) during set up.
From a muscle fiber type perspective, explain how one athlete could be more powerful than another.
greater muscle cross section. attributed to hypertrophy or possibly, a greater proportion of fast twitch (larger cross section and quicker time to peak contraction) Power = (force*distance)/time
40. Which style of lifting is best?
head up, knees bent, spine neutral, load close to body/ between legs
37. Explain how Homer Simpson's posture might predispose him to a lifting injury.
heavier = increased disc pressure large abdominal region = posterior truncal tilt tendency to not bend knees
Define the term "Frame rate" and explain its importance when capturing motion for biomechanical analysis
how many frames are developed/ second highest frame rate possible is req. as to not lose critical frames (toe off)
Explain the term "ecological validity" and provide examples in relation to measuring ground reaction forces.
how well does the measured trial reflective life movements is a recorded step, slightly different to a normal step due to subconscious alterations and awareness of study
74. How can muscle power be increased?
increase speed, strength and coordination
87. How might increased flexibility provide protection from muscle injury?
increasing flexibility increase ROM aswell as safe loading range for that muscle - a flexible musculotendinous unit can bare weight at a range of motion that a stiffer musculotendinous unit would be injured.
133. What is meant by "full-wave rectification"?
integrates positive and negative values to develop pure positive slope
126. What does EMG actually measure?
intramuscular electrical activity
List 3 strategies to prevent an overexertion injury.
keep load at waist height, decrease distance needed to carry
33. What factors are involved in back stress?
load, duration, frequency, body distribution, intra abdominal pressure, position
142. Complete this sentence: Injury occurs when ....
loads exceed tissue failure tolerance
Name the 2 umbrella types of muscle fiber arrangements
longitudinal/ pennate
71. Explain how morphology and neural factors can affect strength.
morphological = muscle cross section, fibre type ratio, lever positioning, non-contractile tissue quality neural = motor unit recruitment, signal freq. (rate coding), inter-muscular coordination, intra-muscular coordination
Describe 2 equipment and 2 technique examples of how the application of biomechanics can play a role in injury risk reduction.
no head high tackles volleyball landing drills headgear for at risk players cricket helmet
76. How are strength and Power related?
not strictly related, some sports may require quick contractions (high power), others may involve high strength over a short period of time javelin vs strongman
113. Explain the main differences between 2D and 3D data collection procedures.
number of cameras space/ area of setup
48. Describe the composition of tendons and explain how they achieve such strength.
organised bundles of collagen fibers running in parallel along the path of tensional stress
23. What is posture and how is it controlled?
orientation of torso and limbs. controlled by visual, vestibular and proprioceptive feedback and adjusted by reflexes and cortical output.
Explain in detail the muscle "length-tension relationship" and provide an example how this relationship can advantage or disadvantage a performer.
peak active tension is about resting length peak total tension increases as the muscle is stretch past resting due to the (almost) exponential increase of passive tension. An athlete can dip immediately before jumping to increase tension in quads and increase their high jump.
Explain the difference between these two types of muscle fiber arrangements and how one of these types can generate greater tension.
pennate increases number of muscle fibres and muscle cross section by aligning fibres obliquely to line of force
22. Explain the difference between postural stress and task-induced stress.
postural stress - position and loading on back task induced stress - heavy/ repetitive stress in a relatively safe position
146. How might a surface that is too hard affect injury rates?
put more stress on athletes body shin splints - long distance running tendinopathy or impulse injury - gymnast landing ariel manoeuvre and absorbing magnitudes of bodyweight with just legs
141. Describe the process involved in stage 2 - Identification of factors and mechanisms of injury.
quantifying factors such as magnitude/ rate of forces on body - properties of materials etc - what techniques contribute to injury etc.
Injury, or the susceptibility to injury is closely linked with which biomechanical variable that can be determined using a force measurement system? Can you explain why?
rate of force loading. a high impulse of tension on musculotendinous tissues beyond their capacity
136. What is meant by noise in an EMG signal?
recorded values not attained from muscle activity
21. Explain what a percentile score is and how they are used in ergonomics.
relates to proportion of people on a bell curve. fit the 5th - 95th percentiles (90%) population
47. Tendons comprise which component of the musculo-tendinous unit?
series elastic component
137. List three sources of noise in an EMG signal.
signal interference activity of deeper/nearby muscles motion artefacts
Describe (with some detail) how you might use a force measuring system to analyse 4 different sporting movements / techniques and list what information could be obtained and why? For example: A device designed to measure punching force might be used to assess whether technique changes exhibit improvements force and power of a punch.
squat - pressure mat to establish proper foot pressure baseball - accelerometer to determine force of bat swing muay thai - assess headgear to determine if it can prevent lethal/ dangerous blows gymnastics - measure ground reaction force required for certain aerial maneuvers
117. Explain the "Sampling Theorem" using video collection as an example.
the process signal must be sampled at a frequency at least TWICE as high as the highest frequency present in the signal itself
65. Explain the term "electromechanical delay" and explain how this may be reduced.
the time between muscle stimulation and when force is enacted upon a bone. this is also shown when attempting to produce peak force, the delay can now be attributed to the graded thresholds of different muscle fibres (1>2a>2b) pre tension - providing tension upon a tendon (and even type 1 fibres) before desired contraction
Running shoes have been shown to affect injury rates in runners. Comment on the aspects of friction, impact and rear foot motion control in relation to running shoes
to begin, an athlete must become accustomed to a new shoe the absorption factors of sole material can provide protectiveness (rate of force loading) the shape and rigidity of shoe can protect or enhance the risk of injury depending on shoe to user relationship (over-pronation) (rear foot control) friction can be too low or high depending on what is required (basketball ACL tear too high) Rear foot control is the ability to limit the amount and rate of pronation immediately after foot strike
30. How is biomechanics linked with ergonomics?
using ergonomics to achieve the most efficient (least strenuous) movement or posture
36. What is a lumbar motion monitor and how might it be used?
vest/belt like device that measures angle between trunk and pelvis during motion to assess safe lifting ROM
List and explain several important and/or limiting factors when observing a skill.
viewing position, lighting, speed, camera settings
91. Should the sampling theorem be considered when collecting force data? Explain your answer.
yes, need a high enough rate so data is not mistranslated. at least 2-4x oscillation rate
78. Discuss how Strength / Power changes can occur neurologically.
- disinhibition of golgi tendon organ - motor unit synchronicity - (learning) muscle timing coordination, inactivation of antagonists, stabilizer activity
80. List several ways that strength / power adaptation can improve the SSC.
- golgi disinhibition - improved stretch reflex - antagonist inhibition - concentric motor unit synchronisation - bone density and tendon stiffness = tolerance to higher load - hypertrophy and hyperplasia - enlarged muscular cross section
79. Discuss how Strength / Power changes can occur due to morphology changes.
- hypertrophy (cross section) - hyperplasia (data is sketchy but indicates this CAN occur in human skeletal muscle over long periods of time) - bone desnity -tendon stiffness
Effective application of ergonomic changes to the workplace should eliminate a number of aspects that are undesirable. List these 5 undesirable aspects.
- inefficiency - fatigue - injury - difficulty - low morale
Be able to explain the process of remediation and note several important considerations.
- one error at a time - balance + & - feedback - verbal, demonstrate, guide through, understanding, avoid overload
How might an ergonomist use anthropometry in designing or modifying a work task/environment?
- tallest dictate fit requirements - shortest dictate reach requirements - which features should be made adjustable and to what end.
32. In relation to back stress, explain the difference between type A, B and C injuries.
A = sudden (big load) B = sequence (mild repetition with bad form and moderate weight C = continuous (poor form over a long period of time)
Increased flexibility can generate a shift in the length-tension relationship for that muscle. Explain this shift and how it occurs
A greater ROM would mean the muscle has a greater distance to generate tension. Data would shift right on the graph. Peak contraction point for the muscle would be in a more extended position. More sarcomeres would be in series at a greater length
What minimum number of reference control points is required for the solution of Direct Linear Transformation?
A min number of six control points on a reference structure with known X, Y and Z co-ordinates is needed for the solution of the DLT.
Several operational characteristics of force transducers can influence the accuracy and reliability of the system. Outline and explain several points of consideration regarding these characteristics.
Adequate system sensitivity Low force detection threshold Low hysteresis Low cross talk Elimination of cable interference Electrical inductance and temp and humidity variations. Large enough area for movement to be recorded No outside vibrations (Can be filtered out)
114. Outline the advantages and disadvantages of using a 3D data collection system versus a 2D system.
Advantages of a 3D data collection system over 2D: an accurate representation of the movement with all of directional movement components (i.e., x, y, z) to be captured is allowed rotational movements to be analysed can extrapolate data to obtain rotational kinematic and kinetic data allows more complete and accurate analysis and refinement of movement patterns Disadvantages of a 3D data collection system over 2D: the cameras required for motion capture are relatively expensive the computer hardware and software is also relatively expensive the complex nature of the set-up of data collection and use of associated software limits 3D data collection to technical specialists because of the type and amount of equipment involved 3D data collection usually only occurs in a laboratory setting, thus the range of skills that can be accurately captured is limited
108. List the advantages and disadvantages of video over cinematography.
Advantages over cinematography: Relatively inexpensive User friendly Immediate result Accurate time scaling Immediate Feedback Disadvantages: - Large File size (storage issues)??
81. What is plyometrics?
Body weight power movement (mostly but not exclusively, jump training).
In addition to those presented in 2D recording, list and explain further problems and sources of error when performing 3D recording.
Calibration - All points must be clearly viewed by majority of cameras Must have known 3D co-ordinates and good accuracy Minimum of 6 control points required for Direct Linear Transformation (DLT) Camera placement o Position must relate to the algorithm chosen for reconstruction of the movement space co-ordinates
Explain each of the following muscle contractions e. Concentric f. Eccentric g. Isometric h. Isokinetic i. Isotonic
Concentric - involves shortening of mm. Eccentric - involves lengthening of mm. Isometric - involves no change in length of mm. Isokinetic - same speed (both con & ecc). Isotonic - same force (both con & ecc).
116. Explain what an analogue to digital converter does.
Conversion of a physiological signal (Voltage) to a computer signal (binary digital code)
84. Define flexibility.
Defined as terminal ROM of a segment
99. Define kinematics.
Describes the motion of human bodies
139. List the three stages in the biomechanical reduction of injury process.
Description of incidence and types of injury Identification of factors and mechanisms of injuries Prevention and reduction of risk
54. Which muscle fiber type generates the greatest isometric force? Explain your answer.
Generally: FT & ST fibers generate approx. the same peak isometric force per cross-sectional area of mm. - However, FT are larger in diameter than ST. - Consequently, individuals or mm with a higher % FT fibers can generate higher magnitudes of torque and power than those with more ST fibers
124. Define Electromyography.
EMG = Electromyogram measures electrical activity within a muscle
There are several forms of data smoothing and filtering that can be applied to kinematic motion raw data. Be able to name and explain several of these processes.
Finite difference technique - Takes a weighted average of the point and the nearest to it - Not usually good enough if you want acceleration data Digital low pass filters - Widely used to filter/remove high frequency noise from digital data - Chops out sudden changes - Human motion approx 6 Hz therefore cut-off at 10 Hz Curve fitting - Essentially involves fitting a smooth curve (drawing a line of best fit) to a series of data points
88. What is a force transducer?
Force transducers give an electrical signal proportional to an applied force
25. What are the 4 main risk factors for musculoskeletal disorders in the workplace?
Force, Posture, Repetition, Duration
The type of surface and properties of these surfaces greatly influence injury risk and rates. List and explain how 5 different surface properties can influence injury rates.
Friction and traction Compliance - Amount of deformation under load Rebound (resilience) - Measure of energy absorbed by the surface that is returned to the striking object - Lack of resilience causes fatigue Hardness - The resistance of a materials surface layer to penetration Force reduction - Expresses the % reduction of max force experienced on a surface compared to concrete o Impact attenuation - IAAF specifies force reduction between 35 & 50%
138. Explain the purpose of using a reference electrode and where it should be placed.
bony landmark - reduce noise by calibrating for tissue without muscle
125. EMG allows us to measure what aspects of muscle function?
Identify which muscles are active Identify when they begin or cease their activity Quantify the magnitude of muscle involvement in motor activity
83. Can resistance training be disadvantageous for an athlete? Explain your answer.
If an athletes goal is swiftest possible power output (sprinter) then resistance training with too high loads can become detrimental - 1rm = slow rep, training muscles and motor units to be strong through slow contraction speeds
123. Explain the problems associated with over and under smoothing.
If the choice of cut off frequency is too low or the data is over smoothed then valuable data will be lost If the cut off frequency is too high or the data is not smoothed enough then unwanted noise will remain. The degree of smoothing from digitized data is often subjective - visual observation decision
60. Explain the process of motor unit activation.
In humans, motor units are generally activated by a volley of nerve impulses. - Rapid successive impulses cause a summation effect progressive elevation in tension until max. tension for that fiber is reached. Slow-twitch muscle fibers are generally innervated by motor units with the lowest functional threshold and are thus recruited first. Fast-twitch fibers are innervated by higher threshold motor units and are activated during rapid & powerful movements.
52. Describe the observable differences between these 3 muscle fiber types.
In order 1>2a>2b: slow to fast contraction slow to fast fatigue thickness
68. Discuss in detail the relationship between neural augmentation and the SSC.
Muscle spindles detect stress in the muscle and cause a muscle to contract as a reflexive response, thereby increasing net contraction. If tension through the tendon is too strong, the golgi tendon organ will detect this and cause a reflexive response to switch the muscle off, thereby reducing net contraction. golgi organ sensitivity can be gradually lowered through exposure to reduce limitations on the SSC (disinhibition)
34. Who is NIOSH and what do they do?
National Institute for Occupational Safety & Health
75. Describe the relationship between muscle contraction velocity and power.
Power increases with increases in velocity only up to a certain point. After peak power is achieved further increases in velocity result in a reduction in the power a muscle can generate
What are the 4 phases of the McPherson model (from lecture notes) of performing a qualitative skill analysis?
Pre-observation Observation Diagnosis Remediation
Name 2 important criteria for an effective approach to qualitative analysis.
Prior knowledge/ Correct viewing angle
27. Why is it important to have ergonomic seating in the workplace?
Prolong spinal health, increase productivity, accomodate all staff, increase morale
Be able to explain the difference between quantitative and qualitative analysis and present examples for each.
Quantitative: Numerical recording or measurement. - Time, EMG, Goniometer, Distance Qualitative: Without tool, based on observation and intrinsic 'feeling'. - Coach observation, Athlete feedback, video playback
129. Describe the differences in EMG electrodes and any limitations in their use?
Surface -only surface muscles -clean skin -susceptible to skin and adipose thickness -susceptible to movement -use during concentric and eccentric -exact field of measure is unknown Fine wire -measure deeper muscles -only isometric (fractured wire) -not reproducible -invasive
67. Discuss in detail the relationship between elastic energy and the SSC.
The shorter (time) the eccentric loading phase is, the more powerful the concentric muscle contraction. Optimal stretch shortening movement would load the muscle eccentrically (stretch phase) as fast as possible to maximise the amount of energy stored by the elastic components. Then transfer or 'unload' the eccentric phase as quickly as possible to recover and utilise as much of the stored energy as possible. If stretch is prolonged before shortening occurs the stored energy is lost thru conversion to heat. Long stretch phases will result in a loss of power through dissipation of stored energy to other structures However excessively fast and/or greater loading will result in injury to musculo-tendinous structures
101. Explain the function a shutter has on camera motion capture.
The shutter allows you to adjust how much light enters and hits the film / sensor
51. List all of the names given to the 3 categories of muscle fiber types.
Type 1 Slow-twitch Oxidative (SO) Type 2a Fast-twitch Oxidative Glycolytic (FOG) Type 2b Fast-twitch Glycolytic (FG)
Other than force platforms, what force measuring devices are often used in human movement analysis?
accelerometer pressure mat PEDAR (in shoe force measurement)
97. Describe 2 of the above force measurement systems.
accelerometer - calculates force with strain gauges by measuring acceleration of limb extremities. velocity is proportional to voltage pressure mat - force platfrom that determines COP at a given time
46. A three component mechanical model of muscle consists of 1 active and 2 passive elements. Name and describe each of these three components.
active - muscle passive - series elastic component(85%): tendons/ connective tissue passive - parellel elastic component (15%): muscular membranes
List several points of consideration when performing 2D data collection for each of the following: j. Cameras k. Calibration l. The background area m. The subjects
background contrast camera positioning (perpendicular) subject ecological validity (performing in 1 plane)