The biceps are located in an easy to find place on the front of your upper arms. These visually noticeable muscles flex when you bend your elbows and raise your hands toward your shoulders. When you do this against a resistance such as a dumbbell or other heavy object, the biceps respond with an increase in size and strength. However, this elbow flexion is only one way the biceps function.
The biceps are a two-headed muscle that begins on your shoulders and shoulder blades and ends on the bones of your lower arms. When the muscle shortens and contracts, your elbows flex. The biceps are easily located, as you can feel them when you squeeze your upper arm.
Along with elbow flexion, the biceps are responsible for forearm supination. The muscle attaches to the radius bone in your lower arm. When the biceps shorten, the muscle pulls on the radius and rotates your hand from a palm-up to a palm-down position, or the reverse. This rotation is the secondary action of the biceps.
A secondary biceps exercise uses the forearm supination movement. You can do this with dumbbells. Hold onto a dumbbell in each hand for your arm curls. At the bottom of the movement, when your arms are straight at your sides, face your palms in toward your body. As you flex your elbows and curl the weights, rotate your palms face up throughout the lift. Near the top of the curl, continue to rotate your palms to face as far out to the sides as you comfortably can.
Secondary biceps exercises may also refer to exercises in which the biceps are secondary movers not primary movers. For example, during back exercises such as pullups and rows, the latissimus dorsi muscle of the back does most of the work. The biceps function as a secondary mover when your elbows flex to pull you up toward the bar, or to pull the weight in during a row.