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Supinator always acts together with biceps, except when the elbow joint is extended. [7] It is the most active muscle in forearm supination during unresisted supination, while biceps becomes increasingly active with heavy loading. [8] Supination strength decreases by 64% if supinator is disabled by, for example, injury. [9]
The origin of a muscle is the bone, typically proximal, which has greater mass and is more stable during a contraction than a muscle's insertion. [14] For example, with the latissimus dorsi muscle, the origin site is the torso, and the insertion is the arm. When this muscle contracts, normally the arm moves due to having less mass than the torso.
In most cases, a physician will diagnose an ulnar collateral ligament injury using a patient’s medical history and a physical examination that includes a valgus stress test. The valgus stress test is performed on both arms and a positive test is indicated by pain on the affected arm that is not present on the uninvolved side.
The biceps is a particularly powerful supinator of the forearm due to the distal attachment of the muscle at the radial tuberosity, on the opposite side of the bone from the supinator muscle. When flexed, the biceps effectively pulls the radius back into its neutral supinated position in concert with the supinator muscle. [14]: 346–347
The supraspinatus (pl.: supraspinati) is a relatively small muscle of the upper back that runs from the supraspinous fossa superior portion of the scapula (shoulder blade) to the greater tubercle of the humerus. It is one of the four rotator cuff muscles and also abducts the arm at the shoulder.
The muscular system is an organ system consisting of skeletal, smooth, and cardiac muscle. It permits movement of the body, maintains posture, and circulates blood throughout the body. [1] The muscular systems in vertebrates are controlled through the nervous system although some muscles (such as the cardiac muscle) can be
Only skeletal and smooth muscles are part of the musculoskeletal system and only the muscles can move the body. Cardiac muscles are found in the heart and are used only to circulate blood; like the smooth muscles, these muscles are not under conscious control. Skeletal muscles are attached to bones and arranged in opposing groups around joints. [8]
Muscle also functions to produce body heat. Muscle contraction is responsible for producing 85% of the body's heat. [65] This heat produced is as a by-product of muscular activity, and is mostly wasted. As a homeostatic response to extreme cold, muscles are signaled to trigger contractions of shivering in order to generate heat. [66]