Muscles worked
The biceps do most of the work. They bend the elbow and also turn the forearm so the palm faces up, which is why they work hardest when your palms face up all the way. Underneath sits the brachialis, which bends the elbow whatever your grip, and the brachioradialis on top of the forearm helps too. Your shoulders and trunk keep your body and upper arms still. Turning your palms to face each other, as in the hammer curl, shifts more of the work to the brachialis and forearm. On an incline bench, with your arms hanging behind you, the biceps work from a more stretched position.
Common mistakes
- Bent wrists. If your wrists bend back or curl in, your forearms take over part of the lift. Keep your wrists straight, in line with your forearms.
- Shoulders creeping up. Under load it is easy to shrug or roll your shoulders forward. Keep your shoulders down and chest up, and let the rep finish when the dumbbell reaches your shoulder.
- Half reps. Stopping halfway down trains only part of the movement and makes sessions hard to compare. Only count reps where your arm straightens at the bottom, and go lighter if you cannot.
Variations and alternatives
- Hammer curl: palms facing each other. Choose it for more forearm work, or if palms up feels awkward on your wrists.
- Incline dumbbell curl: a harder variation where the biceps work from a stretched position. Expect lighter dumbbells.
- Barbell curl: both arms lift one bar, and it is easier to add weight in small steps.
- Band curl: the same movement with a resistance band when you train at home.
Sets and reps
The dumbbell curl is an isolation exercise, and heavy sets of 3 to 5 reps usually just turn into swinging. To build muscle, 8 to 12 reps over 2 to 4 sets works well for most people. For endurance, or if you only have light dumbbells at home, go up towards 12 to 20 reps. The guide to sets and reps explains how to choose.
The jump to the next pair of dumbbells is often big in percentage terms, especially for a muscle as small as the biceps. So add reps first, and move up a pair once you reach the top of your range on every set. That is progressive overload at its simplest. Log the weight and reps for every set.