If your arms look decent from the front but thin from the side, and your forearms have never grown, the reverse curl is probably the exercise you've been skipping. Flip your grip overhand and you train the muscles ordinary curls neglect. Here's the honest guide. A reverse curl is a curl performed with an overhand (palms-down) grip, which shifts the work from the biceps to the brachialis and the forearm extensors — building arm thickness and forearm size that standard curls don't. Here's how to do it.
What the reverse curl trains (the honest mechanics)
The reverse curl uses a pronated (overhand, palms-down) grip, and that hand position dramatically changes which muscles do the work. It de-emphasizes the biceps and heavily targets the brachialis (the muscle beneath the biceps) and especially the brachioradialis and forearm extensors — the top of your forearm. Two payoffs follow. Building the brachialis pushes the biceps upward, adding visible thickness and width to your upper arm. And the forearm extensors are chronically undertrained by curls, rows, and pulls, which all work the flexor side — making the reverse curl a genuine gap-filler for balanced forearm development and bigger arms.
Proper form (the movement)
Stand holding a barbell, EZ-bar, or dumbbells with an overhand grip, hands about shoulder-width, arms hanging at your sides. Then: curl the weight up by flexing your elbows, keeping your elbows pinned at your sides and your wrists straight and firm (don't let them flop back under load). Squeeze at the top, then lower under control to a full stretch. Keep your torso still — no swinging. The cues: overhand grip, elbows tucked, wrists straight, curl with control, squeeze at the top, no body English. An EZ-bar is often kinder to the wrists than a straight bar here.
You'll use much less weight (and that's correct)
An honest expectation-setter: you will be significantly weaker on reverse curls than regular curls, and that's completely normal. The overhand grip puts your arm in a mechanically weaker position and shifts the load onto the brachialis and forearm muscles, which are smaller and less trained than your biceps. Many people can reverse curl roughly half to two-thirds of what they curl normally. The mistake to avoid: using your regular curl weight, then compensating by swinging your body and flicking your wrists. The fix: drop the weight substantially, keep your wrists locked straight, and control every rep. Ego on this exercise just means sore wrists and no forearm growth.
Reverse curl vs hammer curl (the honest difference)
These two are often confused, and the distinction is the grip. A hammer curl uses a neutral grip (palms facing each other) and trains the biceps, brachialis, and brachioradialis — it's a strong overall arm-thickness builder and you can use decent weight. A reverse curl uses a pronated grip (palms down), which hits the brachialis and — uniquely — the forearm extensors on top of the forearm, at the cost of much lighter loading. Honest takeaway: hammer curls for thickness with heavier loading, reverse curls for the extensors and grip-side balance. They overlap but aren't redundant — including both covers your arms more completely than either alone.
Where it fits (pair accordingly)
Use the reverse curl as an arm and forearm accessory on an arm or pull day, typically after your heavier bicep work when lighter weight is appropriate anyway. Pair it with palms-up curls like the preacher curl or spider curl for the biceps, a hammer curl for thickness, and triceps work for balanced arms. Grip and forearm strength built here also carries over to heavy pulling like rows and deadlifts. Use light weight for moderate-to-high reps with strict form. Progress with progressive overload. It builds the muscle; a calorie deficit reveals it.
Quick answers
What does the reverse curl work?
The brachialis and the forearm extensors (top of the forearm), with less biceps involvement than a standard curl.
Why am I so weak at reverse curls?
The overhand grip is a mechanically weaker position and loads smaller, less-trained muscles — using much less weight is normal.
Reverse curl vs hammer curl?
Hammer curls (neutral grip) allow heavier loading for thickness; reverse curls (palms down) uniquely target the forearm extensors.
Do reverse curls build forearms?
Yes — they're one of the few exercises that train the extensor side, which curls and pulls neglect.
Should my wrists bend?
No — keep them straight and firm; letting them flop back under load strains the joint.
Barbell, EZ-bar, or dumbbells?
All work — an EZ-bar is usually the most wrist-friendly.
How many reps?
Moderate-to-high reps (10–15) with light weight and strict form.
Every curl, row, and pull you do trains the underside of your forearm. The reverse curl is one of the few things that trains the top — which is exactly why it's the gap in most people's arms.
The reverse curl builds the brachialis and forearm extensors that standard curling completely misses, adding arm thickness and balanced forearm development. Use an overhand grip, keep your wrists straight and elbows pinned, and check your ego — light weight is correct here. Pair it with hammer curls and palms-up curls, and your arms will finally look as good from the side as the front.