ISSA Trainer Practice Exam 2025 – Complete Study Resource

During a bicep curl, the primary muscle responsible for the action is the biceps brachii, which contracts to lift the weight. The antagonist muscle is one that performs the opposite action. In this case, as the biceps contract to flex the elbow and lift the weight, the triceps muscle, located at the back of the upper arm, must relax to allow this movement to occur. This interplay between the agonist (biceps) and antagonist (triceps) muscles is crucial for joint stabilization and controlled movement. While the other muscles listed may play a role in shoulder stabilization or different movements, they do not directly oppose the biceps' action, thereby reinforcing the triceps' role as the antagonist during this specific exercise.