The ability of muscles to contract makes movement possible. The association of muscle contraction with movement has been known for centuries. In the second century A.D., the physiologist Galen understood that muscles work by pulling rather than by pushing. However, the mechanism remained unresolved until the 1950s.

Muscle contraction does operate by a pulling force. The basic mechanism is widespread in nature, being found in humans and other animals, in smooth, skeletal and heart muscles as well as in movement events at the level of the single cell. Although there are differences in the mechanism of contraction of smooth and skeletal muscle there are also a number of similarities. Basically, two sets of filaments slide over one another, allowing the muscle to shorten. When the filaments slide back in the other direction the muscles attains its original length.

Skeletal muscle is composed of fibers that...