Dumbbell scaption, also called a dumbbell Y, strengthens many muscles in your shoulders and back. This exercise is also commonly used in the prevention and rehabilitation of rotator-cuff-related injuries. In 2006, the American Academy of Orthopaedic Surgeons reported that 4.1 million Americans visited a doctor because of rotator-cuff issues. While this exercise primarily targets the serratus anterior, deltoids and supraspinatus, your rhomboids and lower trapezius also perform an important function during the movement.

How to Perform

Spread your feet no more than shoulder-width apart with your knees partially bent. Grab one dumbbell in each hand and rotate your wrists so your thumbs are pointing toward the ceiling. Bring your shoulder blades together and relax your arms so the dumbbells are next to your thighs. Situate your arms at 45-degrees angles from the midline of your body, so they form an inverted V shape. While keeping your arms straight, elevate your hands upward until they are shoulder height. Hold for 2 to 3 seconds, then gradually lower your hands back to your thighs.

Serratus Anterior

Your serratus anterior muscles are located along your ribs and connect to your shoulder blades. These muscles are responsible for the upward rotation required during the scaption exercise. Weakness in the serratus anterior is associated with poor shoulder motion during throwing activities. Strengthening the serratus anterior with dumbbell scaption can increase the endurance of these muscles, according to research published in "The American Journal of Sports Medicine" in 1999.

Deltoids

Your deltoids are the largest muscles worked during the dumbbell scaption exercise. These muscles are located on the upper portion of your arms, when viewed from the side. The primary responsibility of your deltoid muscles is to elevate, or abduct, your arm away from your body. During the upward phase of scaption, your deltoids activate to perform this task. The front, or anterior, portion of your deltoids works the most, while the posterior portion works the least during this exercise. This means you should choose a rotator-cuff exercise focused on the posterior deltoids, like the bent-over W exercise, to complement this lift.

Supraspinatus

The supraspinatus, like your deltoids, is also responsible for abduction of the shoulder. It runs from the top of your shoulder blade into your humerus. During scaption, the activation of this muscle is greatest at the start; the deltoid takes over as you lift your arm. While this muscle assists the deltoids, its primary function is to stabilize your shoulder. This muscle pulls the top of your humerus bone into your shoulder joint to prevent it from moving in a way that would cause injury to your shoulder.