A pull-up is a closed-chain exercise where you hold onto a bar or a similar apparatus with your hands in a fixed position and pull against gravity to lift your body toward the hands. Although most people would say that your back, shoulders and arms are doing the work, your entire body -- even your legs -- works to stabilize your posture as you pull yourself up and lower yourself down, according to physical therapist Gray Cook, author of "Movement."
Back
Your back muscles consist of the latissimus dorsi, erector spinae, trapezius, multifidi and other spinal muscles along the vertebrae. The deep stabilizing muscles close to your spine and organs keep your spine in place to prevent injury, while the outer muscles toward the skin surface move the body, according to Cook. The moving muscles pull your shoulder blades down and toward the center of your body when they contract in a pull-up.
Arms and Shoulders
Your arms and shoulders provide the anchor to the grip and assist the back muscles to produce force in a pull-up. Your shoulder muscles include the rotator cuffs, deltoids and the stabilizers toward the shoulder joints. Your arm muscles include the triceps, biceps, brachioradialus and all muscles in the forearms and wrists.
Abdominal Muscles
Your abdominal muscles are made up of the inner and outer units like your back muscles. The inner layer stabilizes your torso to maintain your posture, while the outer layer moves your torso in different directions. The inner layer includes the diaphragm, transversus abdominus and internal obliques, while the outer layer includes the rectus abdominus, external obliques and quadratus lumborum, according to physiologist Gerald Tortora, author of the "Principles of Human Anatomy" series. During a pull-up, your abdominal muscles work together with your back and hips to maintain posture to lift your body up more efficiently.
Hips
All hip muscles are connected to your torso by tissues that distribute force and tension. Like your abdominal muscles, your hip muscles, including your buttocks, pelvic floor and hip flexors, stabilize your pelvis and legs to help you lift yourself up.
References
- "Movement"; Gray Cook; 2010
- "Principles of Human Anatomy"; Gerald Tortora; 2003
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