Dumbell curls are one of the best biceps exercises for building big arms. They mainly target the biceps brachii muscle, but also work the brachialis (another muscle under your bicep) and brachioradialis (in your forearm).
Start by holding a dumbbell in each hand down at your sides with your palms facing inwards.
Flexing only at the elbow, curl one dumbbell upwards until it is near your shoulder. As you raise the dumbbell, rotate your forearm outwards so that your palm is facing your shoulder at the top of the movement.
Lower the dumbbell back to the starting position, rotating your forearm inwards again. As you lower the weight, curl up the other dumbbell in the same way and repeat.
Make sure you keep your elbows in close to your body throughout the movement and take care not to lean backwards. Alternate dumbbell curls seem to be one of the exercises that many people perform badly even though it’s a simple exercise. The only joint that should move is the elbow and the weights should be raised and lowered in a slow, controlled manner. Many people can be seen almost throwing the weights up – sloppy form won’t build muscle; it’ll lead to injury.
You can also perform the exercise sat on a bench with the back rest either straight up or at a slight angle. Another variation is the hammer curl where you keep the palms facing inwards during the movement instead of rotating the forearm.