The main function of muscle cells is to produce contractions of the muscle. Impulses are sent through the nervous system along the muscle cells and cause the muscle to contract.
Muscle cells have a membrane called the sarcolemma that allows impulses to travel along the body's muscles. Since most of the human body's muscles act as voluntary muscles, the muscles need the impulses from the nervous system to contract. Muscle contractions allow the body to move, squat, open doors and perform other basic functions. The use of progressive strength training, such as lifting weights, develops the body's muscle cells and increases muscle mass.