Biceps curls may seem simple, but you could be making these super-common mistakes.

By Lauren Mazzo

Ah, the biceps curl. It may seem like the bro-iest of gym moves, but this classic arm exercise is one of the best for building a strong upper body. Strengthening these "pull" muscles will make holding and carrying heavy objects easier, get you closer to the pull-up of your dreams, and, obv, will look really good when you flex.

That being said, there are a lot of major mistakes you can make when doing biceps curls. At best, these form mistakes will keep you from working your biceps in the most effective way. At worst, they could result in injury. Follow these tips from fitness expert Jen Widerstrom (Shape's consulting fitness director and the creator of the 40-Day Crush-Your-Goals Challenge), and watch her demo the perfect biceps curl in the video above. (Also check it out on Instagram TV!) Pro tip: To ensure you're really hitting the right muscles, you can also try a concentration curl-which a recent study found is the most effective biceps exercise out there. Because it locks your elbow in place, it keeps you from swinging your elbow, one of the crucial mistakes listed below.

How to Perform the Perfect Biceps Curl


  • Stand tall with core engaged; think about keeping your chest tall without flaring your ribs forward.
  • Grip dumbbells tightly with wrists flexed, forming a straight line from knuckles to elbow.
  • Leave knees soft.
  • Keep biceps engaged throughout, maintaining tension even at the bottom of the movement.


  • Round upper back.
  • Let dumbbells swing or use momentum to lift them up.
  • Lock your knees.
  • Relax biceps at the bottom.
  • Let wrists flop out or curl in.