The brachialis (G. brachion, arm.) is a lesser-known arm muscle located on the front of the humerus. It is the prime mover in elbow flexion. Since it only crosses one joint, its contribution to elbow flexion is always the same, no matter the position of the shoulder joint or rotation of the forearm. It’s the … Read more

The biceps brachii (L. biceps, two-headed [bis, twice ; caput, head] ; G. brachion, arm.), commonly known as the biceps, is the prominent two-headed muscle of the arm. It acts on the elbow, forearm and shoulder, with it’s main role being a synergist in elbow flexion. Note: The biceps is most active in elbow flexion … Read more

The lower trapezius (G. trapeza, four-sided or four-legged table.) is not an individual muscle, itself, but rather it is the lowermost section of fibers in the trapezius muscle. It acts on the scapula, with its main role as the prime mover in scapular depression. Also worth noting is its important role as a scapular stabilizer: … Read more

The middle trapezius (G. trapeza, four-sided or four-legged table.) refers to the middle section of fibers in the trapezius, between the upper and lower trapezius fibers. It acts on the scapula and is the prime mover in scapular retraction. The middle trapezius is grouped as a superficial posterior axioappendicular (extrinsic shoulder) muscle. It’s situated between … Read more

The teres minor (L. teres, round and long ; minor, smaller.) is a small rotator cuff muscle, which is hidden from the surface of the physique. It acts on the shoulder joint and is a prime mover (along with the infraspinatus) in shoulder external rotation. Like all rotator cuff muscles, it also helps stabilize the … Read more

The teres major (L. teres, round and long ; major, larger.) is a thick, rounded muscle in the posterior shoulder region. It acts on the shoulder joint, with its main function as a synergist in shoulder adduction. It is classified as a one of the scapulohumeral (intrinsic shoulder) muscles, and is visible on the surface … Read more

The supraspinatus (L. supra, above ; spina, spine [of scapula].) is the uppermost muscle of the rotator cuff. It is a synergist in shoulder abduction, being most active during the initial 15° of the range of motion. It also stabilizes the shoulder joint by compressing the humeral head into the glenoid fossa, counteracting the shearing … Read more

The subscapularis (L. sub, beneath ; scapularis, shoulder blade.) is the largest of the four rotator cuff muscles. As its name suggests, it is situated on the underside of the scapula. It acts on the shoulder joint and is the prime mover in shoulder internal rotation. It also promotes shoulder stability by resisting anterior translation … Read more

The latissimus dorsi is the largest muscle in the upper body and the widest muscle in the entire body. It acts mainly on the shoulder joint, being the prime mover in both shoulder adduction and shoulder extension (and a strong synergist in internal rotation). Being such a broad muscle that crosses multiple joints, the latissimus … Read more

The upper trapezius (G. trapeza, four-sided or four-legged table.) refers to the uppermost section fibers on the trapezoid-shaped muscle pair known as the trapezius. The upper trapezius fibers span from the top of the upper back to the base of the skull, and act on the scapula and cervical spine, with their biggest role as … Read more