The reverse curl is a variation of the standard bicep curl, performed using a pronated, or overhand, grip on the barbell or dumbbell. This simple change in wrist position fundamentally alters the distribution of the load among the muscles responsible for bending the elbow. Unlike the traditional curl, which primarily targets the bicep, the reverse curl is strategically used to focus on two lesser-known muscles of the upper arm and forearm.
The Primary Target Muscles
The reverse curl shifts the emphasis of the lift away from the biceps brachii. Instead, the two main muscles recruited are the brachialis and the brachioradialis. The brachialis is located deep beneath the biceps brachii on the upper arm, and its primary function is pure elbow flexion, regardless of the forearm’s rotational position. Because the brachialis is unaffected by the pronated grip, it acts as a powerful and consistent elbow flexor during this movement. Developing this muscle contributes to overall arm thickness by pushing the biceps muscle outward.
The brachioradialis is the second major muscle involved, running along the thumb-side of the forearm from the upper arm bone to the wrist. This forearm muscle is a strong elbow flexor, and its activation is enhanced when the forearm is in a pronated position, as in the reverse curl. The exercise develops the size and strength of the brachioradialis, which contributes to the thickness of the forearm near the elbow joint. While the biceps brachii still assists, its mechanical disadvantage means it takes a less dominant role compared to a standard curl.
How Grip Changes Muscle Activation
The overhand, or pronated, grip is the biomechanical factor that causes the shift in muscle recruitment. The biceps brachii performs two actions: elbow flexion and forearm supination (turning the palm upward). When the palm is turned downward, the muscle’s ability to exert force for flexion is reduced.
The pronated grip shortens the line of pull for the biceps, compromising its leverage and forcing it into a mechanically disadvantaged state. This reduction in efficiency compels the body to rely more heavily on the secondary elbow flexors—the brachialis and the brachioradialis—to lift the weight. The line of pull for the brachialis is not affected by the grip, meaning it must compensate for the de-emphasized biceps. The brachioradialis is recruited in this forearm position to assist in moving the load. This intentional mechanical handicap makes the reverse curl an effective tool for targeting muscles often neglected by traditional curls.
Proper Form and Technique
Performing the reverse curl with correct form is necessary to isolate the intended muscles and avoid wrist strain. Begin by standing with the feet shoulder-width apart, holding the bar or dumbbells with a shoulder-width, overhand grip. The elbows should be kept pinned close to the torso, and the core engaged to prevent swinging.
The weight should be curled upward by bending only at the elbow joint, focusing on squeezing the forearms and the upper arm. Maintain a straight wrist throughout the movement, avoiding extension or “breaking.” The bar is then lowered slowly and with control, emphasizing the eccentric, or negative, phase of the lift.
Controlled lowering benefits the activation of the brachialis muscle. Using a weight that is too heavy often results in excessive momentum or “cheating,” which minimizes targeted muscle work and increases the risk of injury. The goal is to keep the movement strict and deliberate to ensure the brachialis and brachioradialis perform the majority of the work.