Because the pectoralis major flexes the shoulder, adducts and rotates the humerus, and depresses the pectoral girdle, its absence would make such actions as climbing, pushing, throwing, and adducting the arm (as in reaching across to the other side of the chest) difficult. Some synergists that could partially take over these functions include the latissimus dorsi, teres major and minor, coracobrachialis, subscapularis, and anterior portion of the deltoid.
The flexor carpi radialis tendon passes deep to the flexor retinaculum, a tight fibrous band which prevents the tendon from bowing upward during wrist flexion.
(a) Rupture of the calcaneal tendon detaches the gastrocnemius and soleus muscles from the calcaneus (heel bone); contraction of the muscles causes the muscle bellies to draw up into the superior part of the leg and form a prominent bulge there. (b) The dorsal calf muscles normally resist dorsiflexion when they are stretched to their limit. Rupture of the tendon removes this resistance and permits greater dorsiflexion. (c) These dorsal calf muscles produce plantar flexion by lifting the calcaneus. When detached from the calcaneus, they cannot do this. Plantar flexion can then be achieved, to a limited degree, only by weaker muscles such as the plantaris, tibialis posterior, and fibularis brevis and longus.
Habitual wearing of high heels results in shortening of the calf muscles, since they are not stretched when the heel is elevated. Then when a woman goes barefoot or wears flat shoes, these muscles and the calcaneal tendon (and others) are painfully stretched.
In heavy lifting of this sort, the quadriceps femoris and gluteus maximus produce most of the force in extending the knee and hip, respectively.
