AFAA Personal Trainer Certification Practice Exam 2025 - Free Personal Trainer Practice Questions and Study Guide

The triceps are the muscle group that opposes the biceps during arm movement. When the biceps contract to flex the elbow and bring the forearm closer to the shoulder, the triceps must relax to allow this movement to occur smoothly. Conversely, when the triceps contract, they extend the elbow and straighten the arm, which serves to counteract the flexion provided by the biceps.

This opposition is a crucial aspect of muscular balance and coordination, allowing for controlled and efficient movement. The coordination between these two muscle groups is essential for activities that involve arm movement, ensuring that actions are precise and powerful without leading to imbalances or injuries.

The other options listed, such as the deltoids, erector spinae, and abdominals, either assist with different types of movements or stabilize the body in general and are not directly involved in opposing the biceps in elbow flexion and extension.