What is the primary movement caused by the triceps brachii at the elbow?

The primary movement caused by the triceps brachii at the elbow is elbow extension. The triceps brachii is a muscle located on the back of the upper arm and is composed of three heads: the long head, lateral head, and medial head. When the triceps contract, they pull on the olecranon process of the ulna, resulting in the straightening of the elbow joint.

Elbow extension is particularly important for various functional activities, such as pushing movements, throwing, or any action where the arm is straightened from a bent position. This action is the opposite of elbow flexion, which is primarily facilitated by the biceps brachii and involves bending the elbow.

In the context of the choices provided, options related to elbow abduction and adduction do not pertain to the triceps brachii, as those movements involve lateral movement of the arm away from or towards the body, typically associated with shoulder joint actions rather than elbow flexor or extensor actions.