What Are The Actions Of Muscle?

The voluntary or skeletal muscles, which are fastened by means of tendons or sinews to the bones, actually serve as bridges across the joints. It is the group of muscles between the elbow and the shoulder that move the forearm, even as the muscle group between the elbow and the wrist move the hand. A group? Yes a group is needed to make possible the different kinds of movement, and that by means of the tendons. Tendons, however, are not to be confused with the ligaments that link bone to bone and which cannot stretch. When ligaments are stretched, there is a painful sprain.
As for the muscular action itself, there are only two kinds that muscles can perform: They can (1) pull, contract or become tense and (2) relax. They can never push.

Mainly, our voluntary muscles come in pairs or pairs of groups. Groups of two or three are paired to act as antagonists to each other. For example, the three front flexor muscles are able to flex the forearm, and the two extensor muscles in the back of the upper arm can straighten out the forearm. These "antagonists" always cooperate. Thus when the one contracts, the other relaxes, making possible the other's contraction. This, of course, requires coordination of the nerves, the sending of signals to the one set of muscles to contract and at the same time to the opposing group of muscles to relax.