ACSM Personal Trainer Certification Practice Exam

What is the primary action of the triceps brachii at the elbow joint?

1. Flexion

2. Extension

3. Adduction

4. Abduction

The correct answer is: Extension

The primary action of the triceps brachii at the elbow joint is extension. This muscle comprises three heads – the long head, lateral head, and medial head – and is situated at the back of the upper arm. When the triceps brachii contracts, it pulls the forearm away from the upper arm, straightening the elbow joint, which is the movement known as extension. In the context of this muscle's function, it's important to recognize that the triceps brachii is the antagonist to the biceps brachii. When the biceps brachii contracts to produce flexion (bending the arm at the elbow), the triceps brachii serves to counterbalance that movement. Since the question focuses specifically on the action at the elbow joint, extension is the clear choice as it is the primary movement performed by the triceps brachii in this region.