Starting Position: Sit with your back against a backrest so that your head, shoulders and butt make contact with the bench and your feet firmly on the floor. Grasp a dumbbell in each hand with thumbs wrapped around the handles. Your arms are at your sides, close to your body and your palms are facing forward. Pull the shoulder blades down and back.
Upward Phase: Exhale and slowly bend your elbows bringing the dumbbells toward your shoulders. Do not allow your back to arch or your elbows to move forward. Keep the wrists in line with your forearms (neutral). Do not allow the wrists to bend throughout the exercise. Your head, shoulders and butt should stay in contact with the bench. Keep your feet firmly on the floor. Do not allow your shoulders to shrug.
Downward Phase: Inhale. Straighten your elbows and lower the dumbbells back to your start position in a slow and controlled manner.
Variation to this exercise: To emphasize more biceps activity, change your starting position. Turn your palms towards your sides and rotate them forward (or up) during the upward phase before your forearms reach horizontal. During the downward phase rotate your forearms back inward as your forearms reach horizontal. Curl the dumbbells higher by allowing the elbows to move forward as the dumbbell reaches your chest, moving the upper arm towards horizontal with the floor. This places a little more emphasis on the biceps and some anterior shoulder muscles.
As some of us show structural differences at the elbow, we may not be able to hold the dumbbells against our sides in the lowered position unless we force a bend at our wrists. The dumbbell position selected should be one that is most comfortable for you and keeps the wrists aligned straight with the forearm.