ACSM Personal Trainer Certification Practice Exam

The biceps brachii is the primary muscle responsible for elbow flexion during a bicep curl. As the arm is bent at the elbow, the biceps shorten and contract to pull the forearm upward, effectively flexing the elbow joint. This action is essential for performing exercises aimed at strengthening the biceps, such as the bicep curl.

In this movement, the biceps activate to lift the weight against gravity, making them the central muscle group involved in this specific motion. Other muscles, such as the brachialis and brachioradialis, assist in the process, but the biceps are the most prominent muscle at work, particularly when the movement emphasizes the bicep region.

The other muscles listed do not primarily facilitate this movement: the triceps, for instance, are responsible for elbow extension, while the deltoids are mainly involved in shoulder movements. The pectoralis major also does not directly influence elbow flexion, as it primarily affects movements at the shoulder joint. By focusing on the biceps in this context, you target the specific muscle responsible for achieving the desired effect during a bicep curl.