A dumbbell pullover is a weight-lifting exercise that primarily strengthens the muscles of your chest, or pectorals. It also works some of the muscles of your shoulders, upper back and arms. You perform dumbbell pullovers by raising and lowering a dumbbell beyond your head while lying on your back. This exercise will define your upper body and perk up the pecs, giving your bosom a bit of a boost.
Dumbbell pullovers work the pectoralis major muscle that forms the bulk of your chest. It runs from the sternum, or breast bone, and the clavicle, or collarbone, to the top of the humerus, which is your upper arm bone. Pectoralis major adducts and medially rotates your arm. Adduction is the anatomical term for moving a part toward the midline of your body and medial rotation means to turn inwardly. Dumbbell pullovers focus on the sternal portion of the pectoralis major, which is the part closer to the breastbone.
You use more than one muscle when you perform the dumbbell pullover. Synergist muscles assist the primary muscle during a weight lifting exercise. Dumbbell pullover synergists include the latissimus dorsi, which gives your upper back it's V-like shape, the levator scapulae and rhomboids that also help form your upper back, the the deltoid that forms the cap of your shoulder, the triceps muscle at the back of your arm, and the pectoralis minor that lies underneath the pectoralis major.
A few muscles help stabilize your body while you perform an exercise. These muscles are called stabilizers. Muscles that help stabilize during the dumbbell pullovers include the triceps and deltoid, which are also synergists, and the wrist flexors, which are the muscles that bend your wrist toward the front of your forearm. The clavicular portion of the pectoralis major is also a stabilizer.
Lie with your back on a flat bench, or perpendicularly to the bench, with only your shoulders and upper back on the bench. You can also rest your shoulders on an exercise ball. ExRx.net advises against raising your hips up too high during the movement. Keep your elbows slightly bent throughout the exercise. Avoid going beyond the range of motion of your shoulder. The American Council on Exercise suggests you keep your elbows close to each other during the exercise.