If you want bigger upper arms, do curls. But which curl is better: the (dumbbell) biceps curl or the hammer curl?

The short answer: one is not better than the other. With both exercises you train your upper arms in a specific way. So put them both in your program.

DIFFERENCES

The difference between the performance of the biceps curl and hammer curl is the grip: you perform hammer curls with a neutral grip (palms facing inwards) and biceps curls with a supinating grip (palms facing upwards). What is the effect of this difference?

Research suggests that the classic biceps curl lengthens the biceps (officially: biceps brachii) more than the hammer curl, which can benefit the growth of the biceps (both the long head and the short head). Another study shows that biceps curls produce more biceps activation than hammer curls.

At the same time, research shows that hammer curls mainly stimulate the brachialis and brachioradialis, two small muscles that make your upper arms and forearms bigger respectively. This article is about the upper arms and therefore the brachialis is important.

HAMMER CURLS IN BRACHIALIS

With hammer curls you mainly train the brachialis, a small muscle underneath your biceps. Small yet important: if you develop this muscle properly, it pushes your biceps upwards, as it were, which ensures a better biceps peak and therefore, especially optically, a larger size of your upper arms.

By making two adjustments to the exercise you shift the emphasis even more to the brachialis, at the expense of the brachioradialis and the biceps:

• perform the exercise slowly;
• move to the center of your chest.

BICEP CURLS VERSUS HAMMER CURLS

Hammer curls are not necessarily better than bicep curls; they serve a different purpose. While hammer curls target the brachialis a bit more, bicep curls specifically emphasize the biceps. Include both exercises in your schedule (for example, 6 sets of biceps curls and 6 sets of hammer curls every week), and your arms are guaranteed to grow.