Bicep Curl: How to Do It, Muscles Worked and the Best Variations

The bicep curl is the exercise everyone knows, and the one almost everyone does slightly wrong. Curl a weight from your thigh to your shoulder and you work the muscle on the front of your upper arm that most people train for. It needs almost no kit, it is beginner friendly, and it genuinely builds bigger, stronger arms when you do it properly. The catch is that curls are easy to cheat, so a bit of technique goes a long way. Here is how to curl correctly, the muscles it works, and the variations worth adding.

How to do a bicep curl

The steps below describe a standing dumbbell curl, the most useful version to learn first. You only need a pair of dumbbells to start.

1. Set up. Stand tall with a dumbbell in each hand, arms hanging by your sides, palms facing in. Keep your feet shoulder-width apart and your knees soft.
2. Fix your elbows. Tuck your upper arms lightly against your sides and keep them there. Your elbows are the hinge, and they should barely move forward or back during the rep.
3. Curl and rotate. Bend at the elbow to raise the weight, rotating your palm to face up (supinating) as you lift. Squeeze your biceps hard at the top.
4. Control the lowering. Lower the weight slowly, taking around 2 to 3 seconds, until your arm is fully straight and your palm faces in again. The lowering phase builds as much muscle as the lift, so do not just drop it.
5. Keep your body still. No swinging, no leaning back, no shrugging your shoulders. If you need momentum to move the weight, it is too heavy.

Muscles worked

The curl looks like a one-muscle exercise, but three muscles share the job of bending your elbow.

• Biceps brachii. The star of the show, the two-headed muscle on the front of your upper arm. A palms-up grip and a strong squeeze at the top load it hardest.
• Brachialis. Sits underneath the biceps. Because it pushes the biceps upward, a well-developed brachialis makes your arm look thicker. Neutral-grip (hammer) curls hit it well.
• Brachioradialis. A forearm muscle that crosses the elbow. It works more when your palm faces in or down, which is why hammer and reverse curls build the forearms (EMG comparison of three curl variants).

How you hold the weight changes which of these does the most work, because forearm rotation shifts the load between the biceps and the forearm muscles (study on hand position and elbow flexion). That is the whole reason to rotate through different curl variations.

Benefits

• It builds bigger, stronger arms. Direct biceps work adds size that rows and pulldowns alone often leave on the table.
• It supports your bigger lifts. Strong biceps and forearms help your grip and your pulling strength on deadlifts, rows and pull-ups.
• It needs almost nothing. A single pair of dumbbells and a couple of square metres is enough, which makes curls perfect for home training. Adding resistance work like this a couple of times a week fits the NHS advice to strengthen your major muscle groups at least twice a week.
• It is easy to progress. Add a rep, add a little weight, or slow the lowering phase, and you have a clear path to keep improving.

Common mistakes

Swinging the weight. The classic error. Using your hips and back to fling the dumbbell up means your biceps barely work. Stand still and let your arms do the lifting, even if it means going lighter.

Moving your elbows forward. When your elbows drift forward and your shoulders join in, the lift turns into a front raise. Keep your upper arms pinned to your sides.

Half reps. Stopping short at the bottom keeps constant, easy tension but robs you of range. Straighten your arm fully at the bottom of every rep (without locking it hard) so the muscle works through its full length.

Rushing the lowering. Dropping the weight quickly wastes the most productive part of the rep. Take 2 to 3 seconds to lower under control.

Bending your wrists. Curling your wrists back towards your forearm to help lift the weight strains the joint and takes tension off the biceps. Keep your wrists firm and straight.

Variations

Rotate through a few of these to hit every part of the arm and keep progressing.

• Hammer curl. A palms-in grip that targets the brachialis and brachioradialis for thicker arms and stronger forearms. Full detail in our hammer curls guide.
• Incline dumbbell curl. Curl while lying back on an incline bench so your arms hang behind your body. This stretches the biceps and makes the exercise noticeably harder.
• Cable curl. A cable keeps tension on the biceps through the entire rep, top to bottom, which many lifters find gives the best pump and mind-muscle connection.
• Barbell or EZ bar curl. Loading both hands on one bar lets you use more weight, and the EZ bar is kinder to your wrists than a straight bar. See the best EZ bar guide.
• Preacher curl. Resting your arms on a pad removes all momentum and isolates the biceps hard, especially at the bottom. Our preacher curl guide covers the setup.
• Concentration curl. Sitting down with your elbow braced on your inner thigh, one arm at a time, is a classic finisher for peak biceps focus.

Sets and reps

A simple, effective approach for most people:

• Muscle and size: 3 to 4 sets of 8 to 15 reps, one or two times a week. Rest 60 to 90 seconds.
• Beginners: 2 to 3 sets of 10 to 12 reps with a light weight, focusing purely on still elbows and a controlled lower.
• Finisher: pick two variations (say a hammer curl and a cable curl) and do a couple of hard sets of each at the end of an upper-body session.

Add a rep or a small amount of weight once you can complete every set cleanly. Because the biceps also get worked during pulling exercises, you rarely need more than a couple of dedicated curl movements per week.

Recommended reads

1. The best adjustable dumbbells in the UK
2. Hammer curls: how to do them and muscles worked
3. Preacher curl: how to do it
4. The best EZ bar in the UK
5. Forearm exercises for a stronger grip