Starting Position: Sit with your back against a back rest so that your head, shoulders and butt make contact with the bench and place your feet firmly on the floor. Grasp two dumbbells with a closed, supinated grip (palms facing forward and thumbs wrapped around the handles) and let your arms hang to your sides, close to your body, with your palms facing forward. Depress and retract (push down and back) your scapulae (shoulders).
Upward Phase: Exhale and slowly bend each elbow in unison, bringing the dumbbells towards your chest without arching your back or moving your elbows forward. Maintain a neutral wrist position (avoid flexion and extension of your wrists) and keep contact with your head, shoulder and butt against the bench. Keep your feet firmly placed on the floor and avoid shrugging your shoulders during the lift keeping your scapulae (shoulders) depressed and retracted.
Downward Phase: Inhale and gently lower the dumbbells back towards your starting position.
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.