The muscle located underneath your arm and on the side of your torso is the serratus anterior. Named for its serrated design, this muscle extends from the shoulder blade, connecting like fingers to the upper eight or nine ribs. It is the muscle you feel while throwing a baseball, raising your arm, or tossing a bouquet over your head, and it's strengthened during pushups, bench presses or other exercises engaging the scapula.
The serratus anterior muscle often works with the rotator cuff to lift the arms up or above the head. A dumbbell pullover not only works the serratus anterior, but also assists with biceps and triceps development. To execute a dumbbell pullover, sit on a bench with your feet square on the floor. Holding one dumbbell with both hands, extend your arms straight in front of your chest. Bend at the elbows to form a 90-degree angle with your arms and continue by rotating at the shoulders to lift the weight over and behind the head. Lower the dumbbell back to the start position and repeat. Three sets of 10 are recommended.
Traditional pushups assist in developing the serratus anterior, but take it one step further with a pushup plus. Different from a traditional pushup, you won't lower your chest to the floor with a pushup plus. Assume the traditional pushup plank position. Keep your arms straight while dropping your chest toward the floor. You should feel your shoulder blades come together as your chest descends just a few inches. When you push your chest back up you should feel your shoulder blades spread back to their original positions. Keep your back straight and don't allow your head or hips to drop when your chest descends. Moving your hands closer together will open your shoulder blades further, adding more movement to the exercise.
This exercise can be executed lying flat on the floor or on a weight bench. Extend your arms toward the ceiling with a 5- or 10-pound dumbbell in each hand. Open your chest, letting your shoulder blades rest on the supporting surface. Keeping your elbow and wrist straight, lift your shoulder off the supportive surface and push the weight directly toward the ceiling. For an added core workout, you can try this exercise with a stability ball. Three sets of 15 reps are recommended.
You can add another element to pushups to increase their difficulty. Assuming the plank position, or a traditional pushup position, place your hands on an elevated stationary object or surface, such as a plyo box or stair step. Then continue to execute the pushup.
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