The reverse barbell curl primarily works the brachialis, brachioradialis, and biceps brachii, with significant secondary activation in the wrist extensors along the top of the forearm. Flipping to an overhand (pronated) grip changes which muscles do the heavy lifting compared to a standard curl, making this exercise one of the best choices for building thicker forearms and stronger grip.
Primary Muscles Worked
Three muscles share the load during a reverse barbell curl, but they don’t contribute equally. The brachialis, a thick muscle hidden underneath the biceps, is the true powerhouse of this movement. It’s the most powerful elbow flexor in the body, and unlike the biceps, it connects only to the ulna (the non-rotating forearm bone). That means it pulls with the same force regardless of how your wrist is positioned. When you flip to an overhand grip, you’re essentially handicapping the biceps and forcing the brachialis to pick up more of the work.
The brachioradialis, the prominent muscle running along the thumb side of your forearm, gets far more activation in a reverse curl than in a standard curl. This muscle naturally holds the forearm in a neutral position (halfway between palm-up and palm-down), so a pronated grip forces it to work harder to assist with elbow flexion. This is the muscle most responsible for the “forearm thickness” that reverse curls are known for building.
The biceps brachii still contributes, but at a mechanical disadvantage. The biceps is both an elbow flexor and a forearm supinator (it wants to rotate your palm upward). When you lock your grip palm-down, the biceps loses leverage because it can’t perform that supination role. It still fires, but the brachialis and brachioradialis take over as the dominant movers.
Why the Overhand Grip Changes Everything
The shift in muscle recruitment comes down to anatomy. The biceps brachii attaches to the radius, the forearm bone that rotates when you turn your palm up or down. In a standard supinated curl (palms up), the biceps is in its strongest mechanical position because it can both flex the elbow and stabilize the forearm in supination simultaneously. Flip your grip over, and you take away that advantage entirely.
The brachialis, by contrast, attaches to the ulna, which doesn’t rotate at all. Its job is pure elbow flexion regardless of grip orientation, so it works just as hard in a reverse curl as in any other curl variation. The difference is that it’s no longer sharing the workload with a fully engaged biceps. Research published in Sports confirms that the brachialis has no influence on wrist position and doesn’t participate in forearm rotation, making it the one elbow flexor that never loses leverage.
Forearm and Grip Benefits
Beyond the upper arm, reverse curls activate the wrist extensors on the top of your forearm. These muscles work isometrically (holding without moving) to keep your wrist stable under load throughout the curl. Most people overtrain their wrist flexors through pulling movements, rows, and standard curls while neglecting the extensors. Reverse curls help correct that imbalance.
Stronger wrist extensors improve grip strength and wrist stability in ways that carry over to deadlifts, pull-ups, rows, and everyday tasks like carrying groceries or opening jars. If you’ve ever felt your grip fail before your back or biceps during heavy pulls, weak forearm extensors are often part of the problem. Regular reverse curling builds the kind of balanced forearm strength that keeps your grip from becoming a limiting factor.
Straight Bar vs. EZ Bar
A straight barbell places your wrists in full pronation, which maximizes the mechanical disadvantage on the biceps and theoretically gives the brachialis and brachioradialis the greatest possible role. However, full pronation under load can stress the wrist joint, especially as weight increases. Many lifters report discomfort on the outside of the wrist or elbow with a straight bar.
An EZ curl bar angles your grip slightly inward, reducing wrist torque while still keeping the grip close enough to pronated that the brachialis and brachioradialis remain the primary movers. For most people, the EZ bar is the more practical choice for long-term training because it lets you load the movement progressively without wrist pain cutting sessions short. If your wrists feel fine with a straight bar, it’s a valid option. But the muscle recruitment difference between the two is small enough that comfort should be the deciding factor.
How to Program Reverse Curls
Your set and rep scheme depends on what you’re training for. For muscle growth (the most common goal with this exercise), 3 to 4 sets of 8 to 12 reps works well. For grip endurance and forearm conditioning, 3 to 4 sets of 15 or more reps at a lighter weight is effective. Strength-focused training calls for heavier loads in the range of 5 sets of 5 reps, though this is less common for an isolation exercise.
One important practical note: you will use significantly less weight on reverse curls than on standard curls. Dropping to 50 to 60 percent of your normal curl weight is typical and expected. The brachioradialis and wrist extensors are smaller muscles, and the biceps is working at reduced capacity. Ego-loading this exercise is a fast track to wrist strain. Start light, focus on a controlled tempo (especially on the way down), and keep your elbows pinned to your sides. If your elbows drift forward or your body starts swinging, the weight is too heavy.
Where It Fits in Your Training
Reverse curls work best toward the end of an arm or pull day, after your heavier compound movements and standard curls. Placing them last ensures your forearms don’t fatigue early and limit your performance on bigger lifts like rows or chin-ups. They pair naturally with standard curls or hammer curls to cover all three major elbow flexors: the biceps (standard curl), the brachialis (reverse curl), and the brachioradialis (both reverse and hammer curls).
If your primary goal is forearm size and grip strength, reverse curls are one of the most efficient exercises available. If your goal is overall arm development, they fill a gap that standard curls leave open by targeting the brachialis, the muscle that pushes the biceps up from underneath and adds visible width to the upper arm even though the brachialis itself sits out of direct view.