The name of the exercise, supinated dumbbell curls, simply explains the anatomical position, the resistance type and the movement. A supinated position faces your palms up. Dumbbells are hand-held weights used during strength training. The curl movement suggests a decreasing joint angle as you lift the weight toward your body. This exercise is a single-joint exercise, although the muscle it strengthens is a two-joint muscle.
The biceps curl begins with your arms straight at your sides. Your palms face forward with a dumbbell in each hand. Exhale, bend your elbows and raise your hands toward your shoulders. The weight is lifted as high as you comfortably can and as long as you are able to keep your elbows close to your sides. Inhale as you straighten your arms and lower the dumbbells to the beginning position. Keep a slight bend in your elbows at the bottom of the exercise. The curl repeats for your desired number of repetitions. The supinated curl is performed from a standing, seated or lying on a bench position.
The biceps are the muscles that bend your elbows and lift the dumbbells. The biceps begin on the scapula and end on the lower arm bone. Since the biceps cross the elbows, the elbow joint is used during the supinated dumbbell curl. The biceps shorten as the muscle contracts and when the muscle shortens the elbow flexes.
The wrist does not flex or extend during the supinated arm curl, but it is involved in the exercise. To protect your wrist and to focus the muscle concentration on the biceps, the wrists must remain in a neutral position. Neutral is described by the American Council on Exercise as being in a straight line with your forearms. The wrists and the forearm muscles controlling the wrists, remain in a static position as you attempt not to move the wrist joint during the curl.
The biceps attach to the shoulders, but the shoulders should not move during the curl. If the shoulder flexes or extends, the exercise begins to focus on the deltoids instead of the biceps. The shoulders remain stationary and the biceps aid in stabilizing this joint.