Muscle contraction is the tightening, shortening, or lengthening of muscles when you do some activity. It can happen when you hold or pick up something, or when you stretch or exercise with weights.

Howard Hughes Medical Institute researchers have identified two drugs that mimic many of the physiological effects of exercise. The drugs increase the ability of cells to burn fat and are the first ...

The muscular system works to control the movement of our body and internal organs. Muscle tissue contains something called muscle fibers. Muscle fibers consist of a single muscle cell. They help to ...