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Both the extensor and flexor muscles are involved in the maintenance of a constant tone while at rest. In skeletal muscles, this helps maintain a normal posture. Resting muscle tone varies along a bell-shaped curve. Low tone is perceived as "lax, flabby, floppy, mushy, dead weight" and high tone is perceived as "tight, light, strong".
Bone and muscle strengthening exercise, also known as resistant training, decreases fat mass and increases lean mass at the same time, though it does better at the latter. In order to prevent injury from repetitive motion, people should do resistant training with different parts of their bodies on different days.
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.
A decrease in muscle mass may be accompanied by a smaller number and size of the muscle cells as well as lower protein content. [89] Human spaceflight, involving prolonged periods of immobilization and weightlessness is known to result in muscle weakening and atrophy resulting in a loss of as much as 30% of mass in some muscles.
Musculoskeletal physiology is the branch of physiology which addresses the processes of musculoskeletal system. [1]In subclassifying musculoskeletal physiology, MeSH emphasizes the division between "phenomena" and "processes".
Muscular dystrophy is a group of disorders associated with progressive muscle weakness and loss of muscle mass. These disorders are caused by mutations in a person's genes. [ 12 ] The disease affects between 19.8 and 25.1 per 100,000 person-years globally.
Spastic hypertonia involves uncontrollable muscle spasms, stiffening or straightening out of muscles, shock-like contractions of all or part of a group of muscles, and abnormal muscle tone. It is seen in disorders such as cerebral palsy, stroke, and spinal cord injury. Rigidity is a severe state of hypertonia where muscle resistance occurs ...
The muscle fibers belonging to one motor unit can be spread throughout part, or most of the entire muscle, depending on the number of fibers and size of the muscle. [2] [3] When a motor neuron is activated, all of the muscle fibers innervated by the motor neuron are stimulated and contract. The activation of one motor neuron will result in a ...