Pull ups are a difficult exercise that use many arm and upper back muscles. To do pull ups, hang from a bar and lift yourself up by bending and lowering your elbows until your chin is level with the bar. Slowly lower your body back to a hanging position and repeat until you can no longer use good form.
Biceps Brachii
Your biceps brachii, commonly just called biceps, is the primary muscle that bends your elbow. You can easily feel this muscle on the front of your upper arm.
Brachioradialis
Your brachioradialis muscle connects the lower portion of your humerus (upper arm bone) to the far end of your lower arm. It also bends your elbow. According to "Principles of Anatomy and Physiology," by Gerard Tortora and Bryan Derrickson, its primary purpose is slow flexion of the forearm when lifting weights.
Brachialis
Another little-known muscle used in pull ups is the brachialis. Although short, reaching only from the lower humerus to the upper ulna (lower arm bone), the brachialis is the "most powerful flexor of the forearm at the elbow joint," according to Tortora and Derrickson.
Teres Major
Your upper back houses the teres major, which Tortora and Derrickson describe as a "thick, flattened muscle." This muscle pulls the humerus down along the torso when you do pull ups.
Rhomboid
The rhomboid muscle is sometimes distinguished into the rhomboid major and the rhomboid minor. However, "Principles of Anatomy and Physiology" states that both muscles "are used when forcibly lowering the raised upper limbs." They pull your body upward during pull ups to bring your upper arms parallel to your upper body.
Trapezius
The trapezius is a "large, flat, triangular sheet of muscle," according to Tortora and Derrickson. It lies over your middle back, upper back and neck. Frederic Delavier, in "Strength Training Anatomy," explains that the trapezius helps bring the shoulder blades together when you do pull ups.
Latissimus Dorsi
The latissimus dorsi extends from your vertebrae to your humerus, covering your middle and lower back. It pulls your humerus down and back during pull ups. "Strength Training Anatomy" explains that pulling your elbows even with your body uses the lower portion of the latissimus dorsi, which widens your back. However, if you focus on pulling your elbows back, you use the upper portion of this muscle, which thickens your back.
References
- "Principles of Anatomy and Physiology"; Gerard Tortora and Bryan Derrickson; 2006
- "Strength Training Anatomy"; Frederic Delavier; 2006
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