unit 7: muscle mechanics

impingement

shoulder pain caused by connective tissue (a tendon) rubbing on a shoulder blade commonly seen in: - baseball pitching - tennis players - swimmers

chondromalacia

the degeneration of cartilage

two joint muscles

muscles that cross two joints rather than just one, such as the hamstrings, which cross both the hip and the knee

relationship between the abdominal muscles and the hip flexors

- The abdominal muscles (rectus abdominis, external and internal obliques) and the hip flexors (iliopsoas, pectineus, and rectus femoris) work together in order to create maximum ROM in your ability to raise the legs as high as possible. - When you are in good alignment in a standing position and raise one leg (keeping it straight), the hip flexor muscles contract concentrically to raise the leg approximately 30 to 45 degrees (more if you have great hip joint flexibility) the erector spinae muscles remain under isometric contraction in order to stabilize the pelvis - When the leg goes higher than the 30 to 45 degree angle, the pelvic girdle thenrotates posteriorly (upper hips move backwards) to allow the leg to rise higher - At this time, the rectus abdominis and oblique muscles undergo concentric contraction in order to rotate the hips, and the hip flexor muscles switch to an isometric contraction in order to maintain the hip and leg position as a unit and the erector spinae muscles switch to an eccentric contraction in order to control the rotation of the pelvis. - when the leg is behind the body, then the abdominal muscles will have to first undergo a concentric contraction in order to rotate the pelvis posteriorly and bring the leg in alignment with the body - hip flexor muscles at this time remain under an isometric contraction to stabilize the hip-leg unit - if the leg is vertical, the muscular contraction switches and the hip flexors undergo a concentric contraction in order to raise the leg while the pelvis remains stable with an isometric contraction of the erectors.

relationship between the shoulder and the elbow

- The actions of the triceps and biceps muscles at the shoulder joint are secondary to those at the elbow joint - their attachment to the scapula, when doing elbow flexion or extension exercises, the muscles of the shoulder joint must contract in order to stabilize the shoulder and arm - the muscles will have a tendency to perform their actions at both the elbow and shoulder joints - The two heads of the biceps cross the shoulder joint to attach on the scapula their action at the shoulder joint is relatively weak and they come into play only when the resistance is sufficiently great they act mainly as secondary movers and help stabilize the shoulder joint only the long head of the triceps crosses the shoulder joint, it plays a role as a stabilizer and, even more importantly, as a prime mover for shoulder joint extension plays a key role not only at the shoulder but also at the elbow - The rotator cuff muscles handle most of the stabilization work on the posterior shoulder.

shoulder

- The bony arrangement of the shoulder joint consists of a shallow socket (glenoid fossa) into which the spherical head of the humerus fits - Less than half of the humerus is in the socket at any one time, and the bony arrangement is therefore weak - a multi-axial joint (the same as in the hip joint) - allows for the following movements: flexion, extension/hyperextension, transverse (horizontal) adduction and abduction, abduction and adduction, medial (inward) and lateral (outward) rotation, and circumduction - designed for mobility and therefore sacrifices bony and ligamentous stability

relationship between the wrist muscles and the elbow

- The elbow and wrist are connected through the wrist flexor and extensor muscles - muscles cross the wrist and elbow joints (from their attachment on the hand to their attachment on the humerus) they have a role at the elbow as well as the wrist, although they are primarily wrist muscles - At the elbow joint muscles are relatively weak and their angle of pull is more into the joint rather than in moving the forearm their function is to act more as stabilizers when you execute elbow joint exercises - The elbow joint is used in most all upper-body exercises and movements

muscles of the wrist joint

- The major flexors of the wrist are the flexor carpi radialis, flexor carpi ulnaris, and the palmaris longus located on the front of the forearm (i.e., on the palm side of the hand) - The major extensor muscles of the wrist include the extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris located on the back of the forearm (i.e., on the back-of-the-hand side of the forearm) - muscles involved in wrist abduction (radial flexion) include the flexor carpi radialis and extensor carpi radialis longus and brevis - In ulnar flexion (wrist adduction), the flexor carpi ulnaris and the extensor carpi ulnaris are the major muscles involved - both the flexor and extensor muscles participate in the lateral movements of the hand. - wrist flexors and some of the finger flexors have dual functions their muscle mass is located within the forearm and their tendons cross the wrist joint to attach on the bones of the hand the muscles contract and shorten, the tendons also shorten, producing an action in the wrist

spine

- The most important functional unit of the body is the vertebral (spinal) column - the deep and superficial muscles of the back, which produce forward, backward, and lateral bending, and small amounts of rotation of one vertebra on another. - The intervertebral discs allow slight movement and function in shock absorption. - the joint between any two adjacent vertebrae does not allow a great deal of motion, multiple vertebral joints produce a great range of motion in flexion, extension, hyperextension, lateral flexion to both sides, and rotation - The vertebral column lacks great bony stability and relies to a great extent on the ligaments and muscles for support - If they become stretched or weakened, the integrity of the column is weakened and the vertebrae must absorb the forces - The ligaments can hold the vertebral column together, but continued reliance on them as a result of weak muscles or a strength imbalance between antagonist groups of muscles can result in excessive stretching of the ligaments, which becomes permanent. -

shoulder girdle

- made up of the clavicle and the scapula - all movements of the scapula are usually considered movements of the shoulder girdle - these moments include elevation, depression, upward rotation, downward rotation, protraction (abduction), and retraction (adduction) - the shoulder is designed for mobility, its stability is reduced - muscular arrangements of the shoulder girdle and the shoulder joint are such that they provide the stability that is lacking as a result of the weak arrangements of the bones and ligaments - muscles must be strong enough to provide the necessary stability - During forceful overarm motions, the strength of the agonist and antagonist muscles surrounding the shoulder girdle prevents overuse strains on the surrounding tissues. - elevation of the scapula initiates lifting the arm; depression precedes pulling the arm downward; protraction occurs before reaching, throwing, or pushing forward; retraction initiates pulling backward; upward rotation takes place for increasing the range of overhead reaching; and downward rotation allows for forceful arm adduction at the shoulder joint

forearm / radial ulnar joint

- The radioulnar joint is a combination of three joints located at the wrist, elbow, and in between the ulna and radius bones - These joints are not very stable and the surrounding ligaments provide the needed support. - nterosseous membrane, which is located between the shafts of the radius and ulna along their entire length, makes up the middle joint membrane helps to prevent the ulna and radius from sliding past each other. Because the muscles are also attached to the interosseous membrane, it acts to transfer stress from the radius and ulna. - movements consist of pronation and supination - At the elbow, the radius rotates around the annular ligament and does not change positions relative to the ulna - At the wrists, when the forearm is in pronation, the radius crosses over the ulna so that it is then on the inner side of the ulna - When the forearm is in supination, the radius is on the lateral side of the ulna. - The muscles of the radioulnar joint act as stabilizers and produce either pronation or supination: biceps, supinator, pronator teres, and pronator quadratus pronator quadratus and the supinator are situated so that they pull from the ulna on the radius to produce pronation and supination respectively pronator teres has a stabilizing component but also pulls across the elbow and is thus involved in elbow flexion when the resistance is great lso counteracts the pull of the biceps for supination when performing elbow flexion - The attachment of the biceps on the medial side of the radius allows the biceps to produce supination when the forearm is in pronation forearm is pronated, the tendon of the biceps is wrapped around the radius - his positioning causes the biceps to be weak in elbow flexion. This is why a pull-up is easier to perform when the forearm is supinated.

muscles of the spine (mid section)

- abdominal musculature (rectus abdominis, internal and external obliques, transverse abdominis) acts to prevent the vertebral column from continually hyperextending - rectus abdominis acts to pull the anterior pelvis toward the sternum or to pull the rib cage down toward the pelvis - Both of these actions result in spinal flexion in which the rectus abdominis has a large stabilizing component because its line of action is parallel to the spinal column - internal and external obliques are unique in their functions - example, when the right side of the external oblique muscle contracts, it pulls the shoulders down and to the left When the left side of the external oblique muscle contracts, it pulls the shoulders down and to the right - if the pelvis is stabilized, contraction of the upper right external oblique and the lower left internal oblique creates a long pull down and to the left. Contraction of the upper left external oblique and the lower portion of the right internal oblique produces strong downward rotation to the right - If the shoulders are stabilized and the hips are in motion, then movement occurs in the opposite direction the left external and the right internal oblique muscles rotate the right hip up and to the left while the right external and left internal oblique muscles rotate the left hip up and to the right - When the pelvis is in motion the lower latissimus dorsi—which attaches to the upper, outer surface of the pelvis—is also involved - there is some interplay between the muscles of the midsection together with the muscles of the back

ankle and foot

- ankle joint is made up of the tibia and the talus bones. - the end of the tibia is somewhat concave and the talus below it is convex, the bony stability is fairly strong. - Since the ankle must withstand great stress, strong ligaments surround the joint to provide even greater stability. - Movements possible: flexion (dorsiflexion) and extension (plantar flexion). - The axis of rotation for the ankle is not in a true frontal plane. - The tilt creates a slight disorientation of the foot from true anterior-posterior plane motion during plantar flexion and dorsiflexion; in other words, the foot does not remain in the same position during its up-and-down movement - subtalar joint is located between the talus and calcaneus. - This joint is typically involved in ankle sprains or strains. - It is an intertarsal joint (involves several bones of the foot), while the ankle joint has only two bony parts: one in the shin and one in the foot.

the wrist

- consists of the ends of the radius and ulna bones of the forearm with the carpal bones of the hand. - movements of the wrist joint include flexion and extension/hyperextension, radial and ulna flexion (abduction), and adduction, respectively - the bony stability of the wrist is weak, it has fairly strong ligaments to supply stability - muscle tendons cross the wrist on all sides to provide additional stability

major movement possible in the knee joint

- flexion - extension - medial rotation - lateral rotation

muscles of the ankle joint

- gastrocnemius is the major ankle extensor muscle of the shin - located on the upper posterior side of the lower leg and gives the rounded form to the calf. - the upper end are two tendons that attach to the posterior side of the condyles of the femur, while at the lower end, the tendons from the two heads of the muscle run diagonally downward to attach to the Achilles tendon. - directly beneath the gastrocnemius is the soleus - has similar functions to the gastrocnemius - upper attachment is on the tibia and fibula and its lower attachment blends into the Achilles tendon on the calcaneus - soleus is slightly wider than the gastrocnemius - together they form a functional unit sometimes called the triceps surae. - these muscles are extremely strong - when combined with the Achilles tendon, they are even stronger; They can exert a force of over 900 pounds in ankle extension. - tibialis anterior is the main muscle on the anterior side of the shin Its muscle mass is located high on the shin, while its tendon at the lower end crosses the ankle joint and inserts on the inner and under surface of the foot arch.

relationship between the gastrocnemius and the hamstrings

- gastrocnemius, the major muscle of the posterior shin, functions to extend the foot (plantar flexion) - ties in with the hamstrings at the knee joint where they are both involved in knee joint flexion. - the insertion of the gastrocnemius on the femur helps to provide greater stability. - To be most effective, the gastrocnemius must be taut in order to have a strong contraction at the knee joint - The practice of putting one end of a two-jointed muscle on stretch in order to elicit a strong contraction at the other end is very important for maximal development of two-jointed muscles. - muscles include the hamstrings, the rectus femoris of the quadriceps group, the biceps, the long head of the triceps, and others.

the knee

- made up of the end of the femur and tibia bones - ends of these bones consist of two shallow convex surfaces into which semicircular-shaped femoral condyles fit - Because of the shape, the bony stability of the knee is extremely weak. - ligaments help improve stability - the posterior cruciate ligament prevents forward displacement of the femur on the tibia. - The anterior cruciate ligament prevents backward displacement of the femur on the tibia - The medial and lateral ligaments provide stability on the medial and lateral sides - knee joint is stabilized posteriorly by the popliteal ligament and anteriorly by the patellar ligament. - the knee must counteract the negative landing forces in running and jumping and in weightlifting exercises - when the knee is extended, it remains stable because it is surrounded by fairly taut ligaments from all sides and from within - when the knee is flexed, some of the ligaments loosen to allow for greater movement - the muscular arrangement around the knee is extremely important in maintaining the stability needed in order to prevent injury - stabilized on the anterior side by the quadriceps, on the medial side by the sartorius and gracilis, on the lateral side by the tensor fasciae latae (TFL), and on the posterior side by the hamstring muscle group from above and the gastrocnemius from below. - When the leg is bent 80 to 90 degrees or more and the sartorius, gracilis, and gastrocnemius muscles contract, they create a dislocating component at the knee joint. - From 180 degrees (straight leg) to 90 degrees of flexion (bent leg), most of the muscles crossing the knee provide a rotary and stabilizing effect. - When knee flexion is less than 90 degrees, a dislocating component occurs in some of the muscles - also has weak bony and ligamentous arrangements, increasing its vulnerability

the elbow

- made up of the ends of the humerus and ulna bones - Because the radius also articulates with the humerus, it can also be considered part of the elbow. - annular ligament, which encircles the head of the radius and attaches to the ulna, allows the radius to rotate around the ulna on a longitudinal axis of the forearm to provide for pronation and supination - movements possible at the elbow joint are flexion and extension. - The anterior muscles are the main elbow joint flexors (biceps, brachialis, brachioradialis, and pronator teres), which are arranged mechanically around the elbow joint. - the wrist flexors and extensors pass over the elbow to insert on the humerus - the wrist flexor (and extensor) muscles pass so close to the elbow joint that their function at the elbow is mainly stabilizing - stability of the elbow is considered strong due to the number of muscles that act as stabilizers on the anterior side - Positions in which the muscles have dislocating components (when they are at greater than 90 degrees of flexion) occur when the muscles are so shortened that the tension is minimal - The main elbow flexors have stabilizing and rotary functions. - The biceps is most often considered a two-joint muscle. However, it acts on three joints (shoulder, elbow, radioulnar) and should be strengthened in all of these actions - includes shoulder joint flexion with the elbow extended, elbow flexion with the shoulder joint held in extension, and supination with the elbow bent at a 90-degree angle. - The main muscle on the backside of the elbow is the triceps - its attachment on the olecranon process of the ulna, it covers the length of the humerus - the triceps helps to stabilize the elbow when it pulls at an angle greater than 90 degrees to the long axis of the ulna - triceps is a first-class lever when it pulls at a 90-degree angle to the long axis of the ulna. In this position, 100 percent of its effort goes to the rotary function - the triceps is a two-jointed muscle, the long head of the triceps lengthens at the shoulder when shoulder flexion takes place and simultaneously shortens at the elbow end (elbow extension) to allow a full ROM at the shoulder - To fully strengthen all three heads of the triceps, you should do resistance exercises in which you extend the shoulder joint with the elbow extended and extend the elbow with the shoulder joint flexed. (triceps kickback & lying 45 degrees elbow extension)

muscles of the shoulder joint

- musculature surrounding the shoulder joint is arranged so that it produces large stabilizing components especially by the four rotator cuff muscles (supraspinatus, teres minor, infraspinatus, and subscapularis) - the anterior, posterior, and middle deltoids also have large stabilizing components because of their small angle of pull - Further stability is provided by the long heads of the biceps brachii on the anterior shoulder and the triceps on the posterior side - he upward pull of these muscles is counteracted by the downward pull of the rotator cuff muscles (except for the supraspinatus) - The muscles that serve as the primary movers of the arm at the shoulder joint are the deltoid, coracobrachialis, pectoralis major, latissimus dorsi, teres major, the long and short heads of the biceps, and the long head of the triceps on the posterior side - the infraspinatus and the teres minor, also located on the posterior side of the humerus, act in a wheel-and-axle like mechanism to laterally rotate the arm around the longitudinal axis of the humerus - subscapularis, located on the anterior side of the humeral head, also functions in a wheel-and-axle like mechanism to medially rotate the arm functions as a first class lever to pull the top of the humeral head inward - The ROM of the hand when the elbow is flexed during shoulder joint medial rotation varies depending on the amount of elbow flexion - It is greatest at 90 degrees of elbow flexion and smallest when the arm is straight - When the arms are all the way to the rear of the body and the scapulae are retracted (i.e., moved close together), the initial contraction of the muscles on the front of the body (pectoralis major and anterior deltoid) move the head of the humerus more to the front in order to produce horizontal flexion in the shoulder joint. - Problems arise in the shoulder joint if the stabilizing forces are not effective in counteracting the dislocating forces of the muscles involved in the movement. - The action of arm abduction is complex - upraspinatus initiates the first few degrees of shoulder abduction first-class lever arrangement which gives a better angle of pull than does the deltoid muscle - The deltoid does not come into play until the arm is approximately 45 degrees out to the side and up - the scapula rotates about 2 degrees for every 3 degrees of arm movement

muscles of the knee joint

- predominantly two-joint muscles - which cross and act at the hip joint - include the hamstrings, rectus femoris of the quadriceps group, gracilis, sartorius, and TFL muscles - gastrocnemius is another two-joint muscle of the knee, which also crosses the ankle joint - two-joint muscle arrangement provides efficiency of movement in walking and running. - two-joint muscle cannot stretch enough to allow full range of motion at both joints at the same time nor can it contract enough to produce complete movement at both joints at the same time

muscles that perform supination and pronation

- pronator teres - humeral head - ulnar head - pronator quadratus

muscles of the mid section

- rectus abdominis - internal obliques - external obliques - transverse abdominis (underlying) - pectineus - rectus femoris - iliopsoas

relationship between the shoulder joint and the shoulder girdle

- shoulder joint muscles are responsible for moving the arm while the shoulder girdle muscles (which work in synchronization with the shoulder joint muscles) are responsible for moving the scapula (and clavicle) - The muscles work closely with one another to ensure smooth, full ROM in the shoulder joint - The deltoid is strongest from the level position to 180° (when the arms are overhead) and the trapezius works through the full ROM of the arm (0 to 180 degrees) - shoulder girdle muscles can only move the scapulae, and shoulder joint muscles can only move the arm; they work together in all arm movements - 4 sections of the traps -

relationship between the quads and the hamstrings

- the quadriceps should always be stronger than the hamstrings in almost all instances - the quadriceps has four separate muscles, three of which are fairly large. - muscle mass of the quadriceps is much greater than that of the hamstrings, and its workload is also much greater - quadriceps muscles are antigravity muscles that must contract to not only keep you erect but to move you in walking, running, and jumping activities - The hamstrings (at the knee joint) are hardly involved in these activities. In regard to size, only one of the hamstrings (the biceps femoris) has two heads and a substantial amount of muscle mass. - The semitendinosus and semimembranosus have very small muscle bellies - at the hip joint, the hamstrings are stronger than the one muscle of the quadriceps (rectus femoris)

the four sections of the traps

- the very uppermost portion of the trapezius (Part I) is involved in scapular elevation, as seen in the shrug exercise. - (Part II) some of the trapezius muscle fibers are fairly vertical, some are horizontal, and some are in between. The more vertical fibers are involved in elevation of the scapula, while the more horizontal fibers are involved in upward rotation of the scapula - Part IV of the trapezius, the very lowermost portion of the muscle where the fibers are almost vertical, works together with Part II to pull down on the inner border of the scapula to rotate the scapula upward - Part III, the middle part of the trapezius, is involved in adduction of the scapula—movement in which the scapula moves inward toward the spine - Parts II and IV assist in this action, which is also indicative of the importance of this movement. In addition, the rhomboid muscle—which is located directly underneath the trapezius—is also involved in adduction of the scapula - Part IV of the trapezius is also a prime mover for depression in which the scapula moves directly downward. - This is the opposite of elevation, which is performed by Part I. - Depression of the scapula is very important for initiating all downward movements of the arm from an overhead position

exercise analysis questions

1. if the exercise is effective, why is is effective 2. what is the role of each joint action 3. which actions can be changed to make the technique more effective 4. how can joint body or limb movements be changed to bring in greater involvement of specific muscles 5. how can specific actions be made more powerful 6. should the exercise be modified if so how

hamstring group

The biceps femoris (attached on the lateral side) and the semimembranosus and semitendinosus (attached on the medial side of the knee) produce lateral and medial rotation, respectively, when the knee is flexed

the knee joint anterior view (p163)

left side: - femur - lateral collateral ligament - lateral meniscus - fibula right side - articular cartilage - anterior cruciate ligament - medial meniscus - medial collateral ligament - tibia

antigravity muscle

a hypothetical force by which a body of positive mass would repel a body fo negative mass

muscles of the forearm

anterior - biceps brachii - long head - short head - brachiais - bicipital aponeurosis - brachioradialis - pronator teres - flexor carpi radialis - palmaris longus - flexor carpi ulnaris - pronator quadratus - flexor retinaculum - palmar aponeurosis - tendons of flexor digtorum superficialis - tendons of flexor digtorum profundus posterior - triceps btachii - brachiotadialis - anconeus - extensor carpi radialis longus - extensor carpi radialis brevis - flexor carpi ulnaris - abductor pollicis longus - extensor digiti minimi - extensor pollicis brevis - extensor digitorum - extensor pollicis longus - extensor retinaculum

muscles of the shoulder girdle

back ( posterior) - trapezius - rhomboids (underlying) front (anterior) - serrates anterior - pectoralis minor (underlying)

muscles of the know joint

back (posterior view) - gracilis - hamstring group - semitendinosus - bicep femoris - semimemnranosus - gastrocnemius front (anterior view) - tensor - fasciae latae - rectus femoris - sartorius

muscles of the shoulders

back (posterior) - coracobrachialis - teres minor - teres major - triceps - triceps brachii (short head) - triceps brachii (long head) - latissimus dorsi front (anterior) - deltoid - posterior deltoid - medial deltoid - anterior deltoid - pectoralis major - clavicular pectoralis major - sternal pectoralis major - bicpeps brachii - biceps brachii ( long head) - biceps brachii (short head)

muscles of the elbow

back (posterior) - triceps - triceps brachii (lateral heal) - triceps brachii (long head) - acnoneus (underlying) front (anterior) - biceps brachii - biceps brachii (long head) - biceps brachii (short head) - brachioradialis - pronator teres (underlying)

muscles of the ankle and foot

back (posterior) - gastrocnemius - soleus front (anterior) - tibialis anterior

hamstring group and quadriceps group

back (posterior) - semitendinosus - bicep femoris - semimembranousus front (anterior) - vastus intermedus (underlying) - rectus femoris - vastus lateralis - vastus medialis

hyperextension

extension of a limb or part beyond the normal limit