Which muscle controls the action at the elbow for a movement such as the downward stroke in hammering a nail?

The primary muscle responsible for controlling the action at the elbow during a downward movement, such as hammering a nail, is the triceps brachii. This muscle is located on the back of the upper arm and plays a crucial role in extending the elbow joint.

When performing a downward stroke, the triceps brachii contracts to straighten the arm, allowing for forceful and controlled movement. This extension is essential for any action where the arm moves from a flexed position to a straight position, particularly when applying force, as in hammering.

The biceps brachii, while involved in elbow flexion, is not the muscle predominantly engaged in this specific action. Similarly, the pectoralis major and latissimus dorsi muscles are more involved in movements related to shoulder actions rather than direct control of the elbow during the downward hammering stroke. This distinction highlights the specialized function of the triceps brachii in facilitating extension at the elbow during dynamic activities like hammering.