The pectoralis major (L. pectus, chest ; major, larger.) is a large, fan-shaped chest muscle. It acts on the shoulder and (indirectly on) the scapula, with its most prominent role being the prime mover in shoulder horizontal adduction. The pec major is the largest and most superficial of the anterior axioappendicular muscles, lying superficial to the entire pectoralis minor … Read more

The rhomboid major and minor (L. rhomboideus, parallelogram ; major, larger ; minor, smaller.) are two muscles located between the shoulder blades and spinal column. If you took geometry, you might’ve guessed that they’re named after the rhombus shape, which they both resemble. Acting on the shoulder blades, both of these muscles are prime movers … Read more

The levator scapulae (L. levator, elevator ; scapulae, shoulder blades.) is a strap-like muscle in neck and shoulder region. It acts on the scapula and cervical spine, and as its name reveals, its most prominent role is scapular elevation. Classified as a superficial posterior axioappendicular (extrinsic shoulder) muscle, the levator scapulae is situated deep to … Read more

The infraspinatus (L. infra, below ; spinus, spine [of scapula]) is a thick rotator cuff muscle covering the majority of the posterior surface of the shoulder blade below the scapular spine. It is a prime mover in shoulder external rotation and plays important roles in shoulder stability. Most notably, it prevents excessive anterior and posterior … Read more

The transversus abdominis (L. transversus, crosswise [trans, across ; vertere, to turn] ; abdo, to hide.) is a flat layer of muscle in the abdomen, whose fibers run transverse relative to the midline of the body. It is responsible for compressing the abdominal wall, helping to support and protect the internal organs, and assist in … Read more

The external oblique (L. externus, external ; obliquus, oblique.) is a broad, flat sheet of muscle on either side of the abs. It is named after its location (external to the internal oblique) and its fiber direction (oblique relative to the midline of the body). It is the prime mover in spinal rotation, and it … Read more

The serratus anterior (L. serratus, saw ; anterior, front.), named for its saw-like appearance, is located on the side of the ribcage. It acts on the scapula and is the prime mover in both scapular protraction and scapular upward rotation. It’s also a key scapular stabilizer, keeping the shoulder blades against the ribcage when at … Read more

The pronator quadratus is (L. pronus, lying face down ; quadrus, square.) is a rectangular muscle on the front of the forearm that connects between the radius and the ulna. It is the prime mover in forearm pronation, receiving help from the pronator teres during rapid pronation. It is also noted for its role in preventing … Read more

The supinator (L. supinare, to lay on back or turn up) is a relatively wide muscle on the upper forearm. It spirals from the back and outside of the forearm to the front, crossing over the space between the radius and ulna… …This unique location allows it to carry out its primary function of forearm supination. Note: It … Read more

The gluteus maximus (G. gloutos, buttock. L. maximus, largest.) is not only the largest buttock muscle, but the largest muscle in the human body, period. Its main responsibility is hip extension, and it’s classified as part of the superficial gluteal region. The gluteus maximus is the outermost buttock muscle. It lies superficial to the gluteus minimus and the … Read more