chapter 3

muscular balance involves

1) equal strength and flexibility on the right and left sides of the body 2) proportional strength ratios in opposing muscle groups, although they may not be exactly equal 3) a balance in flexibility, in that normal ranges of motion are achieved but not exceeded

most mobile joint in the body

G/H joint movement in all three planes flexion an dextension in the sagittal plane abduction and adduction in the frontal plane circumduction in a combination of the safittal and frontal planes linternal and external roattion and horizatal flexion and extension in the transverse plane refer page 137

law of intertia (newtons first law)

a body at rest will stay at rest and that a body in motion will stay in motion unless acted upon by an external force

supine hip abduction/adduction with the hips extended (121)

abduction (concentrically) of the hip joints occurs as the legs move further apart (hip adductors contract eccentrically), while the adductors control the movement of the legs together (concentrically) (and the hip abductors contract eccentrically)

Medial hip primary adductors and internal rotators

adductor magnus adductor longus adductor brevis as the hip joint is increasingly flexed toward 90 degrees, the most imporatnt internal rotators of the hip are the adductor longus and brevis muscles, gluteus medius, and minimus, pectineus, and tensor fasciae latae there are no true primary internal rotators of the hip for movements starting from the anatomical postiion , beccause no single msucle has a superior mechanical advantage over another to produce internal rotation torque

lower trapezius

angled obliquely downward concentric activity of the lower trapezius fibers will both depress and adduct the scapula

upper trapezius

angled upward and obliquely if the upper fibes are activated concentrically, they will produce elevation an adduction of the scapula

medial leg muscles invertors

anterior tibialis (located ont he front of the tibia and is a key muscle for dorsiflexion in the sagittal plane) posterior tibialis (antagonist of AT, found on the posterior aspect of the tibia and acting as a plantarflexor. act as synergists in the frontal plane

stability limits

are boundaries of an area of space in which the body can maintain its position without changing the base of support (without taking a step)

synergist muscles

assist the agonist in causing a desired action the may act as joint stabilizers or may neutralize rotation or be activated when the external resistance increases or the agonist becomess fatigued

What are the hamstrings referred to as

biarticular group of muscles, producing knee flexion as well as hip extension when acting concentrically

outer layer of core anatomy

big powerful muscles that spann many vertebrae and are involved in gross movement of the trunk rectus abdominis erector spinae group external and internal oblique iliopsoas

serratus anterior

broad knife edged mucle that inserts along the underside of the entire length of the medial border of the scapula and originates on the front parts of the first through ninth ribs abducts the scapula synergist with the upper trapezius to produce upward rotation of the scapula key function is to hold the medial border of the scapula firmly against the rub cage, preventing winging the scapula away from the thorax concentric action - enables powerful forward motion of the arm, as in an overhead throwing motion strengthening - supineposition with the shoulder flexed to 90 degrees and th eelbow extended, by pushing a dumbbell or medicine ball held in the hand toward the ceiling in a punching motion without bending the elbow, the shoulder blanes should loift off the floor slightly when perfroming this exercise also have clients perfrom push ups with a plus - the addition of scapular abduction at the end of the upward phase of a regular push up

motive force

causes an increase in speed or a change in direction

the three normal curves of posture

cervical region - convex (anteriorly) lumbar region - convex (anteriorly) thoracic region - concave (anteriorly)

actions that are multiplanar

circumduction - motion that describes a cone; combines flexion, abduction, extension, and adduction in sequential order opposition - thumb movement unique to primates and humans tha tfollows a semicircle toward the little finger

curvilinear motion

combines translatory and rotary movements to accomplish certain tasks, such as reaching for an object. in this case, the forearm and heand move straight forward because of rotary motion at the shoulder and elbow similar to the path of a ball thrown through the air. a small gliding motion within the joint combines with the more obvious rotary motion of the segment. the gliding within the joint slightly changes the axis of rotation throughout the movement, particularly at the knee and shoulder, and is an important part of normal movement patterns

rotator cuff

comprised of four small muscles, act synergistically to pull the head of the humerus down and into the glenoiid fossa thus helping to stabilize the GH joint against the constant downward pull of gravity acting to dislocate the joint remember SITS Supraspinatus (superior to the spine of the scapula, initiates abduction and is a prime mover through the early abduction range of motion Infraspinatus (found inferior (below) the spine of the scapula, and the Teres minor are synergists for external rotation of the GH joint subscapularis (located on the anterior undersurface of the scapula, is not easily palpated and attaches to the anterior aspect of the joint -- since it is located anterior and medial, the subscapularis functions as an internal rotator of the humerus

hip extensors working concentrically and eccentrically

concentrically - muscles extend the hip joint against gravity, such as during a prone leg lift eccentrically - controlling hip flexion (motion during downward phase of squat or lunge)

iliopsoas

contains 3 muscles iliacus ( origin on th einner surface of the ilium bone of the hip and inserts into the lesser trochanter of the femur) psoas major psoas minor (both originate on the transverse processes of the five lumbar vertebrae and attach to the femur at the lesser trochanter)

glenohumeral joint and scapulothoracic articualtion work together to produce ______________________

coordinated flexion and extension inthe sagittal polane and abduction and adduction in the frontal plane called scapulohumeral rhythm 2 degrees of humeral motion for every 1 degree of scapular motion

flat back

decreased anterior lumbar curve decrease in the normal inward curve of the lower back, with the pelvis in posterior tilt

sway back

decreased anterior lumbar curve and increased posterior thoracic curve from neutral a loing outward curve of the thoracic spine with a decreased anterior lumbar curve and a backward shift of the upper trunk (rounded shoulders, sunken chest, forward tilted head)

shoulder joint complex

describes the coordinated functioning of four separate upper extremily segments the junction of the sternum and the proximal clavicle the acromioclavicular (A/C) joint the junction of the acromion process of the scapula with the distal clavicle the G/H joint, the ball and socket joint composed of the scapula and the humeral head the S/T articulation, the muscles and fascia connecting the scapulae to the thorax scapulothoracic articulation = shoulder girdle

anterior deltoid

easily palpated in the front of the shoulder, attaching to the lateral one third of the clavicle it crosses the shoudler joint anteriorly -- it flexes, internally rotates, an dhorizontally flexes the arm at the shoulder to strengthen - sitting or standing, using free weights or elastic tubing, individuals can perform fron tshoulder raises in sets of eight to 12 repetitions

elastic resistance of hip abductors (121)

elastic tubing is utilized so that concentric muscle actions of the hip abductors occur when the exerciser moves the legs away from the midline, increasing the resistence in the elastic tubing. eccentric muscle actions occur in the hip abductors during the return to the starting position against the force suppled by th eelastic band at the lower leg

anatomical movements of the scapulae on the thorax

elevation and depression addutction (retraction) and abduction (protraction) upward and downward rotation

law of reaction (newtons third law)

every applied force is accompanied by an equal and opposite reaction force. For every action there is an equal and opposite reaction.

lordosis (more common)

excessive anterior curvature of the spine that typically occurs at the low back, but may also occur at the neck. low back pain mostly in pregnant women and people with abdominal fat if maintained, the back extensor and hip flexor muscles will adapt by losing their extensibility and adaptively shorten, the hamstring and abdominal muscles will lengthen under these constant loads, becoming more lax and further decreasing their control of the pelvis

kyphosis (more common)

excessive posterior curvature of the spine, typically seen in the thoracic region gives the humpback characteristic, with rounded shoulders, sunken chest, and head forward posture with neck hyperextension. common among older adults

middle deltoid

fibers are aligned perfectly with the frontal plane, and thus this muscles is the prime mover in concentric abduction of the shoulder joint (upward phase of seated shoulder press) during the downward phase MD acts eccentrically to control the lowering of the weight via adduction when performing overhead resistance training, such as a shoulder press, it is important to maintain the glenohumeral joint in neutral or external rotation

deltoid

fibers running in three different directions an dthree names, according to location. as a whole lies superior toth eglenohumeral joint and collectvely functions as the primary abductor of the shoulder joint.

Posterior knee muscles flexors and rotators

flexors semitendinosus (internal rotators of knee also) semimembranosus (internal rotators of knee also) biceps femoris (external rotators of knee also)

push ups

for advanced exercisers utilize a step bench as the starting position for the hands to increase the level sof difficulty of the push up, or have th eindividual place two bences close together, positioning on ehand on each and performing the push up between the benches. increased height off the ground will permit a larger range of motion during the eccentric and concentric phases of the push up, creating a greater overload of these muscles. ballistic (plyometric) push ups elicited significantly higher levels of muscles activation in upper extremity and core musculature than did push ups performed with the hands on unstable surfaces

erector spinae group of muscles

formed by the iliocostalis, longissimus, and spinalis produce trunk extension and hyperextension also act eccentrically to control flexion of the spine from a standing position (i.e, bending over to pick up something) when stimulated unilaterally, they cause lateral flexion to theat same side exercises to strengthen prone trunk hyperextension lift pg 135 3-28a simultaneous lifting of the opposite arm and leg 3-28b advanced trunk extension with half ball 3-29

middle layer of core anatomy

forms a box spanning several vertebrae, from the giaphragm to the pelvic floor, with muscles and fascia enclosing the back, front, and sides transverse abdominis multifidi quadratus lumborum posterior fivers of th einternal oblique diaphragm pelvic floor musculature and adjoining fascia box allow the spine and sacroiliac joint oto stiffen in anticipation of loading and movement, an dproves a working foundation from which the body can operate

internal oblique muscles

found deep to the external obliques, fibers run diagonally downward and posteriorly, as if into the back pockets of a pair of pants functions include flexion, lateral flexion, and rotation of the trunk to the same side exercises include supine pelvic tilts reverse abdominal curls oblique reverse abdominal curls side lying torso raises

hip abductors

found posterior and lateral to the hip joint (buttocks) Gluteus Medius Gluteus Minimus Superior fibers of Gluteus Maximus Origins: superior to the joint Concentric action of 3 muscles - the hip is pulled away from the midline of the body into abduction

actions of the frontal plane

frontal plane divides the body into front and back abduction - motion away from the midline of the body (or body part adduction - motion toward themidline of the body (or body part) elevation - moving the scapula to a superior position depression - moving th escapula to an inferior position inversion - lifting th emedial border of the foot (subtalar joint only) eversion - lifting the lateral border of the foot (subtalar joint only)

posterior leg muscles plantarflexors

gastrocnemius and soleus combine distally to form th eAchilles tendon, the largest tendon in the body, which attaches posteriorly to the calcaneus gastrocnemius acts at both the knee and the ankle, the soleus only works at the ankle joint pg 48 fig 1-39 pg 124 fig 3-19

primary hip extensors

hamstrings (biceps femoris, semitendinosus, semimembranosus) gluteus maximus

stretching the hamstrings

have the individual assume a position that places the targeted limb in hip flexion and knee extension individual will put the foot of the leg to be stretched on a step and slowly bend forward at teh waist, keeping a flat back (neutral spine position) (123) to increase intensity of this stretch, have the individual flex the knee and hip of the limb not being stretched

to stretch the erector spinae

have the individual assume an all fours position with the hands directly beneth the shoulders and the knees directly beneath the hips, and arch the back like a cat and then transition to the camel position. 3-30

to stretch the external rotator muscles

have the individual lie flat on his or her back and pull the flexed knee and hip diagonally across the body. this position inviles adduction and internal rotation, which effectively stretches these muscles.

to stretch the iliopsoas

have the individual stand in a forward lunge position with the fron tknee flexed and the back leg straight with the foot flat on the floor. instruct him or her in how to activate the abdominal muscles to slightly flex the lumbar spine and hold this position for at least 15 secs.

segments of the upper extremity

head neck shoulder girdle (scapulothoracic (S/T) articulation shoulders elbows wrists hands

gluteus maximus as prime mover

higher intensity activities (stationary cycling, stair climbing, sprinting) need gluteus maximus for greater hip ranges of motion

gluteus medius primary function

hip abduction (0-40 degrees) after 40 degrees the six external rotators are the prime movers anterior fibers attach medially to the hip joint axis for rotation, and produce internal rotation when acting concentrically the posterior fibers of the medius insert lateral to the hips axis for rotation, and thus will create external rotation when activated concentrically

Gluteus maximus primary function

hip extension concentric activation of the superior fibers of gluteus maximus will produce abduction while the inferior fibers will produce adduction

rotary motion

if an object is tied down at a fixred point, it turns around that fixed point in rotary (angular) motion, much like a tetherball. Body segments generally move in rotary motion as they totate around the joint at one end (the fixed point)

understanding concentric and eccentric muscle actions

if the movement direction is opposite the pull of gravity, the active muscle is working concentrically; if the direction of movement is the same as the pull of gravity, then the muscle is working eccentrically. when gravity is eliminated during during movements that are perpendicular to the floor, each muscle group act concentrically to produce the desired motion

prime movers for hip flexion

iliopsoas rectus femoris sartorius tensor fasciae latae act synergistically to cause hip flexion (straight leg raise or knee lift)

anterior tibialis

inersets on the medial aspect of the foot and combines with the posterior tibialis to serve as the prime movers for invresion of the foot warming these muscles: toe tapping, walking around on heels before exercise

deep layer of core anatomy

inner unit consists of small muscles (rotatores, interspinali, intertransversarii) offer stabilization of each vertebra, especially at end ranges of motion, and are rich in sensory nerve indings that proved feeback information to th ebrain relating to spinal position

kinematics

involves the study of the form, pattern, or sequence of movement without regard foir the forces that may produce that motion

joint stability

is the ability to maintain or control jolint movement or position

joint mobility

is the range of uninhibited movement around a joint or body segment

screw-home mechanism

knee joint rotation is only possible in flexed joint positions increases knee joint stability by locking the femur on the tibia (or vice-versa) when the knee is fully extended

scoliosis

lateral spinal curvature often accompanied by vertebral rotation more common

strengthening the pectoralis major

lie supine on a mat or step bench with hand held weights from this position a pectoral fly exercise involving horizontal flexion will overload the pectoralis major the push up is also an affective exercise for the pectoral muscles pectoralis major, serratus anterior, and triceps brachii act eccentrically to slowly lower the body int he downeward phase of the push up (same direction of movemnt as the force of gravity) same mucles act concentrically during the upward phase of the push up`

quadriceps femoris

little activity during relaxed standing as most of the body weight is borne statically onthe joint surfaces of the lower extremity stand --> sit (eccentrically) sit --> stand (concentrically as prime mover to extend the knee) quads needed for lifting heavy objects, walking, and climbing stairs. squats lunges, and stepping are important exercises limit knee flexion to no more than 90 degrees during weightbearing exercises

Six external rotators of the hip

located deep to the gluteus maximus From superior to inferior piriformis, superior gemellus, obturator internus, inferior gemellus, obturator externus, and quadratus femoris orientation of the muscle fibers in this group is horizontal and this makes them highly efficient external rotators of the hip. when the hip is extended, the gluteus maximus also functions as an external rotator

posterior deltoid

located on the backside of the GH joint and acts as an antagonist tot he anterior deltoid. the posterior deltoid has the exact opposite functions as the anterior deltoid, it extends, externally rotates, and horizontally extends the arm at the shoulder to strengthen - ahve the individual assume a staggered stance position with a neutral spine. using hand weights, begin with the shoulder flexed, adducted, and internally rotated, and move into extension abduction, and external rotation

sartorius

longest muscle in the body origin - anterior superior iliac spine (ASIS) insertion - medial tibia, just below the knee actions - flexes, abducts, externally rotates the hip, internally rotates the knee

anterior shoulder girdle muscles

major anterior shoulder girdle muscles pectoralis minor serratus anterior attach the scapula to the front of the thorax, have no attachment to the humerus concentric and eccentric activity in these muslces results in scapular movement on the thorax, these muscles do not attach to the humerus

core anatomy

more superficial muscles are primarily responsible for movement and force transfer between the pelvis and rib cage smaller deeper muscles are more responsible for intersegmental motion and stabilization of the spine

agonist (prime mover)

muscle that causes a desired motion

anterior leg muscles dorsiflexors

muscles of the anterior compartment of the lower leg anterior tibialis extensor digitorum longus extensor hallucis longus dorsiflexion of the ankle (concentrically) walking and running (to eccentrically lower the foot to the ground) these muscles work together as shock absorbers

antagonists

muscles that have the potential to oppose the action of the agonist ex. if shoulder flexion is the desired action (without gravity as a factor), the shoudler flexors are the agonists and the shoulder extensors are the antagonists

forces

muscular forces aare considered internal forces when the body as a whole is the reference point. when the joint or joint axis is the reference point, muscular forces are classified as external because they act outside the joint itself

static isometric action

no visible movement occurs and the resistance matches the muscular tension. the resistance may come from the opposing muscle group (co-contraction) asometric action is also used in proprioceptive neuromuscular facilitation (PNF) stretching techniques can be used in balance and stabilization training and may be included in strength training programs

hamstring as prime mover

normal walking and other low intensity movements. There is some gluteus maximus activity during these movements

oblique exercises

oblique abdominal curls side lying torso raises oblique reverse abdominal curls

general plane motion

occurs when motions at various joints are simultaneously linear and rotary

external oblique

origin: ribs attach: iliac crest and the aponeurosis o fthe rectus abdominis, fibers run diagonally down and forward when acting concentrically, they produce trunk flexion can be activated independently to produce lateral flexion when combined with concentric action of the opposite internal oblique, produce trunk rotation to the opposite side

pectoralis minor

originates on the third, fourth, and fifth ribs and inserts on the coracoid process of the scapula can have a positive or negative effect on posture concentric activity of the pectoralis minor results in abduction, depression, and downward rotation of the scapula. IF the scapular adductors are weak, fatigued, or injured, the muscular tension created by the pectorialis minor will tilt the scapulae forward and down, worsening a rounded shoulders posture (kyphosis)

clavicular portion of pectoralis major

originating on the anterior aspect of the clavicle, is located slightly superior to the GH joint and acts concentrically as a flexor the similar downward oblique angles of the fibvers of the sternal and costal portions ofthe pectoralis major allow them to be considered one functional unit

GH joint muscles

pectoralis major deltoid rotator cuff latissimus dorsi teres major

how to strengthen the iliopsoas

perform a rested knee lift

lateral leg muscles evertors

peroneus longus an dperoneus brevis are muscles found in the lateral tibial compartment that are responsible for eversion of the foot (pulling the foot laterally in the frontal plane) tendons of these muscles curve around behind the lateral malleolus and attach on the foot both play secondary roles as plantarflexors at the ankle due to their posterior location relative to the axis of motion of the talocrural (ankle) joint

flexibility of gastrocnemius and soleus

pg 124-125

exercises for rectus abdominis

posterior pelvic tilts supine abdoiminal curls reverse abdominal curls abdominal crunches concentric actions during flexion of the trunk, and eccentric during the extension/return phase of the crunch

remaining six muscles of the lower leg

posterior tibialis flexor hallucis longus flexor digitorum longus plantaris peroneus longus peroneus brevis play secondary functinal roles in producing the propulsion force required for human locomotion

sternal and costal portions of pectoralis major

powerful shoulder extensors

middle trapezius

purely horizontal in their direction and pull stimulation of these fibers will cause pure adduction of the scapula

anterior knee muscles knee extensors

quadriceps femoris (composed of four different muscles located on the femur that work together to extend the knee. vastus lateralis (proximal femur) vastus medialis (proximal femur) vastus intermedius (proximal femur) rectus femoris (crosses the hip joint and produces hip flexion when acting concentrically, a function made possible by its origin on the anterior inferior iliac spine quadriceps muscles combine distally to form the patellar tendon (second largest tendon in the body)

abdominal muscles

rectus abdominis external oblique internal oblique transverse abdominis

resistive force

resists the motion of another external force in weight training the contracting muscle may be the motive force (tending to cause motion), while gravity (acting on the body segment and the dumbbell) is the resistive force in that it resists the motion of the motive force) in the return phase of the same biceps curl, the opposite occurs; the motive force is gravity, which causes downward motion. the elbow flexor contraction in the return phase resists the downward motion and is the resistive force

four types of motion

rotary translatory curvilinear general plane motion

actions of the sagittal plane

sagittal plane divides the body into two halves flexion - decreasing the angle between two bones extension - increasing th eangle between two bones hyperextension - increasing the angle between ttwo bones beyond anatomical position (continuing extension past neutral) dorsiflexsion - moving the top of the foot toward the shin (ankle only) plantarflexion - moving the sole of the foot downward (ankle only)

secondary knee flexors

sartorius popliteus (responsible for initiating knee flexion and unlocking the knee from its extended position) gastrocnemius gracilis

tensor fasciae latae

short muscle, very long tendon that combines with tendon fibers from the lower fibers of the gluteus maximus to form the iliotibial band origin - ASIS (anterior superior iliac spine) insertion - lateral tibia just below the knee

strengthening the upper trapezius

shoulder shrugs with dumbbells or tubing with the arms extended behind

exercises that recruit adductors of the hip

side lying leg lifts (lower leg) supine hip abduction/adducting with the hips extended

hips abduction and adduction exercises

side-lying leg lifts (upper leg) side lying leg lifts (lower leg) supine hip abduction/adduction with the hips extended concentric action of the hip abductors with elastic resistance

latissimus dorsi and teres major

similar in function lat dorsi originates over a wide area in the lower thoracic and all of the lumbar regions of the spine teres major arises from the inferior poertion of the scapula functionally similar because of the close proximity of their insertion sites on th emedial aspect of th eproximal humerus. both muscles act concentrically to produce aduction, extension, and internla rotation of the GH joint strengthening - with elastic resistance or a cable pulley machine, starting with the arms overhead and adducting and extending the GH joint against the resistance provided by the tubing or machine. performing this same exercise with dumbbells will not involve the lat dorsi and teres major in adduction, but rather recruit the abductors (deltoids) eccentrically to lower the weights. fitness professionals must be sure theat the initial effort is in a direction opposite the pull of gravity

law of acceleration (newtons second law)

states that the force acting on a body in a given direction is equal to the bodys mass multiplied by the bodys acceleration in that direction F=ma

kinetics

the branch of mechanics that describes the efffects of forces on the body

open chain exercise

the end o fthe chain farthest form the body is free, suc as a seated leg extension.

closed-chain movement

the end of the chain farthest from the body is fixed, such as a squat where the feet are fixed on the ground and the rest of the leg chain moves.

axis of rotation

the imaginary line or point about which the lever rotates. it intersects the center of the joint and is perpendicular to the plane of movement the axis of rotation is in the frontal plane for movements occurring in the sagittal plane. the axis of rotation is in the sagittal plane for movements occurring in the frontal plane. the axis or rotation is called longitudinal for movemtn occurring in the transverse plane

trapezius

the largest and most superficial of the posterior shoulder girdle muscles, it originates at the base of the skull and has attachments to all 19 vertebrae in the cervical and thoracic regions of the spine attached laterally to the spine of the scapula and the lateral aspect of the clavicle divided into three distinct units - upper, middle, and lower

human body center of gravity

the location of the COG in the ever changing human body is the point at which its mass is considered to concentrate and where it is balanced on either side in all planes. in an average person, this point is generally located at the level of the second sacral vertebra, but it changes from person to person, depending on build

eccentric (lengthening) action

the muscle is producing force and is "lengthening" or returning to its resting length from a shortened position. the muscle gives in to, or is overwhlemed by, the external force and can be thought of as putting on the brakes or slowing the descent of a weight occurs when an external force exceeds the contractile force generated by a muscle ex. the biceps brachii act eccentrically in the return phase of a beceps curl performed with a dumbbell

concentric (shortening) action

the muscle shortens and overcomes the resistive force ex. the biceps brachii act concentrically in teh up phase of a biceps curl with a dumbbell

strengthening the middle trapezius

the muscles must be used to lift some resistance against gravity examples of antigravity positions inlclude a fully prone or a simulated prone position (forward lunge, half-kneeling with the torso supported on the front thigh). using dumbbells, the desired movement in the modified forward lunge position is to squeeze the shoulder blades together, causing the arms to lift in the direction opposite the pull of gravity use elastic bands or surgical tubing to provide resistance, abduct the GH joint to 90 degrees, maintain a neutral spine, and then pull scapulae together with no movement at the elbows or wrists

what is happening muscularly when the arms are lifted in front GH flexion or out to the side GH abduction

the shoulder blades rotate uupward and away from the spine this upward rotation occurs as a result of the upper an dmiddle trapezius, rhomboids, and serratus anterior pulling on different aaspects of the scapula. concentric action of the lower trapezius, together with eccentric activity in the rhomboids and levator scapulae, will return the shoulder blades toi their original position

rectus femoris

to strengthen - standing straight leg raise to stretch - perform the iliopsoas lunge stretch, then lower the body so that the back knee bends Concentric action results in hip flexion, knee extension, or both at the same time

key muscle that works with the neural subsystem

transverse abdominis functions primarily to increase intra abdominal pressure , reucing compressive forces aalong the spine

how to activate transverse abdominis muslces

transverse abdominis and multifidi muscles aare thought to play a vital role in providing feedback about spinal joint position, and thus forewarn the central nervous system about imporeding dynamic forces to be created in th eextremities that may destabilize the spine have individual lie on their back with their knees flexed and feet flat on the floor have them visualize pulling their navel inward toward the spine hold this position fo rseveral second, relax, and the repeat several times refer to pages 134-135 for more exercises

actions of the transverse plane

transverse plane divides body into top and bottom rotation - medial (inward) or lateral (outward) turning abou tth evertical axis of bone in the transverse plane pronation - 1. of the forearm, rotating the hand an dwrist from the elbow to the palm down position (elblow flexed) or back (elblow extended) 2. of the foot, rotation so that the sole of the foot faces somewhat laterally and th eweight is borne on the inside edge of the foot supination - 1. of th efoearm, totating the hand and wirst form the elbow to the palm up position (elbow flexed) or forward (elbow extended) 2. of the foot, rotation so that the sole of the foot faces somewhat medially and the weight of borne on the outside edge of the foot horizontal flexion - from a 90-degree abducted arm position, the humerus moves toward th emidline of th ebody in the transverse plane horizontal extension - the return fo the humerus flromhorizontal flexion (adduction) to 90-degree abduction

posterior shoulder girdle muscles

trapezius rhomboids levator scapulae attach the scapula to the back of the thorax, no attachment to the humerus (no GH motion)

side lying leg lifts (121)

upper leg - abductors work concentrically in the upward phase and eccentrically in the downward phase lower leg - adductors work concentrically in the upward phase and eccentrically in the downward phase

pectoralis major

very large muscles that makes up the majority of the muscle mass on the anterior chest wall divided into three sections, with each portion named for its attachment point to the axial skeleton; clavicular, sternal, and costal prime mover in glenohumeral adduction, internal rotation, and horizontal flexion

torque

when a force acts on a lever at some distance from the axis of rotation, a turning effect occurs themagnitude of torque is found by multiplying the amoiunt of force by the length of the lever arm

translatory motion

when an object in motion is not tied down and moves in a straight line, it moves in translatory or linear motion; all parts move in the same direction and at the same speed

isometric action

when muscle tension is created, but no apparent change in length occurs

co-contraction

when the agonist and antagonists contract together and a joint must be stabilized. it is an important component of functional or usable strength because the torso muscles must be able to stabilize the spine to safely move external resistance. the muscles that co-contract toi protect a joint and maintain alignment are called stabilizers

concentric action

when the muscle acts as the motive force, it shortens as it creates muscle tension

eccentric action

when the muscle acts as the resistive force, it lengthens as it creates muscle tension

rhomboid major and minor

work together as one functional unit, the fibers of these muscles run upward and obliquely from the spine to the vertebral border of the scapulae act primarily to adduct and elevate the scapulae and assist with downward rotation of the scapulae when th erhomboids are weak or overstressed, the shoulder blades may tilt and pull away from the thorax dur to the unopposed tension exerted by the srratus anterior and pectoralis minor. bent over rows with a weighted bar or pulley machine weights or the use of a rowing ergometer are effective in strengthening the rhomboids