Big forearms are a statement. Most guys hit the gym, crush some bicep curls, maybe do a few sets of standard wrist curls over a bench, and then wonder why their sleeves still feel loose. Honestly, the standard approach is often lacking. If you want that thick, "Popeye" look, you've gotta hit the flexors from a different angle. That’s where the behind the back wrist curl comes in. It’s a bit awkward at first. You’re standing there, barbell dangling behind your glutes, looking like you’re trying to hide a piece of equipment. But for pure hypertrophy of the forearm flexors? It’s hard to beat.
Most people overlook this move because it feels restrictive. You can’t see the muscle working. You can’t admire the pump in the mirror as easily. Yet, the biomechanics are sound. By positioning the load behind your body, you change the tension curve. It's a different beast entirely.
What Is the Behind the Back Wrist Curl Anyway?
Basically, you’re standing upright. You hold a barbell or a pair of dumbbells behind your thighs with an overhand grip—though, since your hands are behind you, your palms are facing away from your body. The movement is tiny. You let the bar roll down into your fingertips, then curl it back up into your palms, squeezing the life out of your forearms at the top.
It’s a classic old-school bodybuilding staple. Guys like Lee Priest and Bill Pearl swore by various wrist movements, and this specific variation was a favorite for building that dense, meaty look on the underside of the arm. The primary target is the flexor carpi ulnaris and the flexor carpi radialis. These are the muscles responsible for pulling your hand toward your inner forearm.
The range of motion is short. Don't expect to move the bar six inches. If you’re doing it right, we’re talking maybe two or three inches of actual travel. But that’s all you need. The tension is constant because gravity is pulling the bar straight down, and your arms are already in an extended position behind your midline.
Why This Move Destroys Standard Bench Curls
When you do wrist curls over a bench, it’s easy to cheat. You start using your shoulders or leaning your body weight into it. With the behind the back wrist curl, your body acts as a natural stopper. Your glutes and hamstrings are right there, preventing you from swinging the weight excessively. You’re forced to rely on the forearms.
It’s also way better for your wrists in the long run. Many lifters find that resting their forearms on a flat bench creates uncomfortable pressure on the carpal tunnel area or the ulnar nerve. Standing up removes that direct compression. It feels more "athletic."
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Think about it. In real life—like carrying heavy groceries or a suitcase—you aren't sitting down with your arms on a bench. You’re standing. Your grip needs to be strong in an upright posture. This exercise mimics that postural demand while isolating the flexors.
The Finger Roll Secret
If you aren't rolling the bar, you're missing half the gains. Seriously. The forearm flexors also control your fingers. To get the full benefit of the behind the back wrist curl, you have to open your hands at the bottom. Let the bar slide down until it’s caught by the first knuckles of your fingers.
Then, initiate the move by curling your fingers back in. This "roll" engages the flexor digitorum profundus. It’s a deep muscle, but it adds significant girth to the forearm. Once the bar is back in your palm, then you perform the actual wrist curl. It’s a two-part movement disguised as one. Smoothness is key here. If you're jerky, you'll drop the bar or tweak a tendon.
Setting Up for Success (Without Looking Silly)
Use a squat rack. Set the J-hooks at about mid-thigh height. It’s much easier to walk backward into the bar than it is to deadlift it and try to shimmy it behind your butt.
Grip width matters. Most people go too wide. Your hands should be just outside your hips. If they’re too wide, you’ll feel a weird "tweak" in your elbows. Too narrow, and the bar will keep hitting your hamstrings.
Stand tall. Don't slouch. Keep your chest up. If you lean forward, you turn it into a weird shrug-curl hybrid. Stay vertical.
The Thumb Debate. Some lifters prefer a thumbless grip (suicide grip) for this. It allows the bar to roll further down the fingers. Try both. Honestly, the thumbless version feels more "pure" for the flexors, but if you're using heavy weight, keep those thumbs wrapped for safety.
Weight Selection: Don't Be a Hero
This isn't a deadlift. Nobody cares how much you behind-the-back curl. If you go too heavy, your range of motion will disappear. You'll start doing these weird mini-shrugs with your traps to move the weight.
Start with just the bar. Or even light dumbbells. Feel the burn. If you can’t get 15 clean reps with a massive pump, the weight is too heavy. High volume is usually the ticket for forearms. They’re used to being worked all day—holding phones, driving, typing—so you have to really stress them to force adaptation.
Common Mistakes That Kill Your Progress
The biggest sin? Using the traps. Since the bar is behind you, it’s tempting to shrug your shoulders to help the weight up. If your traps are sore the next day, you failed. Keep your shoulders depressed and "locked" down.
Another issue is the "bounce." People use momentum to kick the bar up. Stop. Hold the contraction at the top for a full second. Count it. "One Mississippi." Then lower it slowly. The eccentric (lowering) phase is where a lot of muscle damage—the good kind—happens.
Watch out for your ego. You’ll see guys loading up plates, but their wrists are barely moving. It’s better to do 40 pounds with a full finger roll and a hard squeeze than 135 pounds with a half-inch twitch.
Variations and Tools
You don't just have to use a straight barbell. In fact, a Smith Machine is actually great for the behind the back wrist curl. Because the bar is on a fixed track, you don't have to worry about it swinging away from your body or hitting your legs. You can focus 100% on the squeeze.
Dumbbells are another solid option. They allow for a more natural wrist path. Our wrists aren't designed to be locked into a perfectly straight line. Using dumbbells lets your hands tilt slightly, which can be a lifesaver if you have existing wrist pain or limited mobility.
- Smith Machine: Perfect for beginners. Stability is built-in.
- EZ-Curl Bar: Can be used, but the "waves" in the bar might make the finger roll feel uneven.
- Cables: Attach a straight bar to a low pulley. Stand facing away from the machine. This provides constant tension even at the very bottom of the movement where a barbell might lose its "heavy" feel.
Integrating it Into Your Split
Don't do these before your heavy back or pull-day. If your forearms are fried, your grip will fail on deadlifts or rows. That’s a recipe for a bad workout.
The best time for the behind the back wrist curl is at the very end of a session. Treat them like calves. They are an "accessory" muscle. Hit them 2-3 times a week.
A simple protocol:
3 sets of 15-20 reps.
Rest 60 seconds between sets.
On the final set, do a "drop set." Lower the weight and go to absolute failure. Your forearms should feel like they're about to explode. That's the goal.
The Science of Forearm Growth
Hypertrophy in the forearms is notoriously difficult for some. A lot of it is genetic—specifically, muscle belly length. If you have high muscle bellies and long tendons, your forearms might never look "huge," but they can certainly get thicker.
Research suggests that high-frequency training works well for these smaller muscle groups. Because they are primarily composed of slow-twitch fibers (designed for endurance), they recover quickly. However, you still need to apply mechanical tension. The behind the back wrist curl provides that tension in a way that’s hard to replicate with just "holding heavy things."
While "farmer's walks" are great for isometric strength, they don't take the wrist through a full range of motion. To actually grow the muscle tissue, you need that eccentric and concentric action. You need the curl.
Anatomy Check
The flexor group is actually quite complex. You have the Palmaris longus (which some people actually don't have—it's an evolutionary leftover), the Flexor carpi radialis, and the Flexor carpi ulnaris. These all converge near the elbow. This is why people with tendonitis (Golfer's Elbow) often feel pain during wrist curls.
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If you feel sharp pain near the bony bump on the inside of your elbow, stop. You might be overworking the tendons. Lighten the load, focus on the stretch, and maybe increase the reps while decreasing the weight.
Actionable Next Steps
To actually see results from the behind the back wrist curl, consistency is the only way forward. Start by adding this movement to the end of your next two "pull" or "arm" workouts. Focus specifically on the finger-roll portion of the lift, as this is the most neglected part of forearm training.
Record your weight and reps. Aim to add just 2.5 to 5 pounds every two weeks, or simply try to squeeze out two more reps with the same weight. If you find your grip failing during other lifts, move these to a separate "finisher" day. Within four to six weeks of dedicated effort, the increased thickness in your lower arms should be visible, especially when viewed from the side or back. Keep the movement slow, avoid the shrug, and let the forearms do the heavy lifting.