What primary action does the triceps brachii perform?

The triceps brachii primarily performs elbow extension. This muscle, located at the back of the upper arm, is responsible for extending the forearm at the elbow joint. During activities such as pushing, throwing, or even certain gym exercises, the triceps is engaged to push the forearm away from the body, effectively increasing the angle at the elbow.

Understanding its role is crucial for both strength training and rehabilitation contexts, where promoting elbow extension can help in improving overall arm functionality and strength. The other actions listed, such as shoulder flexion and abduction, do not involve the triceps brachii at all, as they pertain to movements facilitated primarily by other muscle groups, such as the deltoids or pectorals. Elbow flexion, on the other hand, is performed primarily by the biceps brachii and other flexor muscles, firmly distinguishing the triceps' function from that action.