WJEC General Certificate of Secondary Education (GCSE) PE Practice Test

In a bicep curl, the elbow flexion is produced mainly by the biceps brachii, which contracts and shortens to lift the forearm. This makes it the agonist, the primary muscle driving the movement. The triceps sits on the opposite side of the elbow and lengthens as the curl happens, acting as the antagonist to control the motion and prevent the elbow from extending too quickly. The deltoid can help stabilize the shoulder and may assist a bit with the overall positioning, but it is not the main elbow flexor. The abdominals aren’t involved in this elbow action.