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
The gluteus medius (G. gloutos, buttock. L. medius, middle) is the second largest of the three gluteal, or butt, muscles. It is a fan-shaped muscle, whose main action is hip abduction. It is also noted for its essential role as a hip stabilizer in the gait cycle. The gluteus medius is classified as part of the superficial gluteal … Read more
The gluteus minimus (G. gloutos, buttock. L. minimus, smallest) is the smallest and deepest of the three buttock muscles. Its primary responsibility is hip abduction. It is like a mini version of the gluteus medius, sharing a similar shape, location and function. The gluteus minimus constitutes part of the superficial gluteal region. It is in the deepest … Read more
The average gym rat uses the term “hamstrings” to refer to the muscles on the back of thigh, whose primary function is knee flexion. If you want to get really technical, “hamstrings” technically refer to the tendons on either end of the posterior thigh muscles, namely the semitendinosus, semimembranosus and biceps femoris (which includes both … Read more