When Being Antagonistic Is A Good Thing!

Bones, as we know from our study of anatomy, cannot generate movement by themselves; they are moved by muscles. Essentially, the tendons at either end of a muscle attach to adjacent bones at a joint. When the muscle contracts, it pulls the bones, causing the joint to move.

Since the tendons have fixed points of origin and insertion, a muscle can only move a joint in one direction. To return the joint to its original position, an opposing muscle is required.

This opposing muscle works to reverse the movement initiated by the first muscle. The muscle responsible for the movement is called the agonist, or prime mover, while the muscle that relaxes or lengthens to allow the movement is the antagonist. This working relationship between two muscles is known as an antagonistic muscle pair.

A classic example of such a pair is the biceps and triceps. During a bicep curl, the biceps (the agonist) contract to lift the forearm, while the triceps (the antagonist) relax. To lower the forearm, the roles switch: the triceps contract (becoming the agonist), and the biceps relax (becoming the antagonist).

Here are further examples of antagonistic muscle pairs:

The agonist is considered the prime mover because it performs the action, but the antagonist plays an equally important role. Antagonistic muscles help maintain stability, such as when holding the arms out to the side, or controlling rapid movements, like a boxer throwing fast punches in shadow boxing.

In conclusion, both agonists and antagonists are essential for smooth and efficient movement.

Interestingly, there are cases where a muscle can act as its own antagonist. The deltoid muscle is an example, as its posterior fibers rotate the shoulder laterally, while its anterior fibers rotate it medially, making the deltoid an antagonist to itself.

View all messages