Curls, which is the shortened term for bicep curls, are a common weight training exercise used to develop muscles in the upper limbs. Curling can be completed with dumbbells, a barbell, on a pulley unit or on a machine. To perform the curl, hold the weights down by your side with your palms facing forward. Keep your elbows close to your torso as you bend the elbows and bring the weights up to your shoulders. Control the weight back down to the start position.
Biceps and Forearms
Your biceps brachii muscle is located at the front of your upper arm. It originates up at your scapula at the shoulder and then runs down your upper arm and inserts on your radius bone in your lower arm. When it contracts it causes elbow flexion, or makes your elbows bend. Your forearms, or wrist flexors, consist of the flexor digitorium superficialis, flexor digitorum profundus, flexor carpi radialis, flexor carpi ulnaris, palmaris longus and flexor pollicis longus. Together, they perform wrist flexion.
Muscles for Bicep Curls
Bicep curls primarily recruit your biceps brachii muscle in each of your arms. Your brachialis and brachioradialis assist in the movement, while your deltoids, trapezius, levator scapulae and wrist flexors stabilize surrounding joints.
Increasing Bicep Size
Bicep curls are effective at recruiting your biceps and thus can be used to build size, as long as they are completed at an appropriate frequency and volume. At least eight sets are needed to stimulate muscle growth. Therefore, you would need to complete eight sets of bicep curls to adequately overload your biceps and cause them to increase in size. Each set should consist of five to 12 repetitions. Because of the high volume of your workouts, according to Keith E. Cinea of the National Strength and Conditioning Association, your biceps are likely to need about 72 hours of rest in between sessions, so a Monday and Thursday or a Tuesday and Friday schedule would be appropriate.
Increasing Forearm Size
Because your forearms, or wrist flexors, only work as stabilizers and are not the primary muscles used in the bicep curl, bicep curls are not effective at building forearm muscle size. To more effectively target your forearms, complete wrist curls. Sit on the edge of a bench while holding a dumbbell in one hand. Position your forearm on your thigh with your wrist extended just beyond your knee joint and your palm facing up. Extend your wrist to allow the dumbbell to lower below your knee joint and then raise the dumbbell back up as high as possible. Complete at least eight sets to stimulate muscle growth.