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.

People can build muscle by using their muscles more, such as by lifting weights or working out. Eating enough calories and protein is also important. Skeletal muscle is one of the three major muscle ...

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 ...