College of Massage Therapists of British Columbia (CMTBC) Practice Exam

Which muscle primarily acts as the antagonist to the biceps brachii?

1. triceps brachii

2. brachialis

3. pectoralis major

4. latissimus dorsi

The correct answer is: triceps brachii

The triceps brachii is primarily recognized as the antagonist to the biceps brachii due to its functional role in the arm's movement. The biceps brachii is responsible for elbow flexion and supination of the forearm. When the biceps contracts to perform these actions, the triceps brachii must relax to allow the movement to occur. Conversely, when the triceps brachii contracts, it performs elbow extension, opposing the flexion performed by the biceps brachii. Antagonistic muscles work in pairs, where one muscle contracts while the other relaxes, allowing smooth and coordinated movement. The triceps brachii’s position and function specifically counter the actions of the biceps, making it the primary antagonist in this context. Other muscles mentioned, like the brachialis, assist the biceps in flexing the elbow rather than opposing it. The pectoralis major and latissimus dorsi are involved in different movements, primarily concerning the shoulder and upper limb motion, rather than acting as direct antagonists to elbow flexion.