Muscle cells are cells in the body that are adapted for movement by contracting and relaxing. These cells are specialized to contract, creating a pulling force that allows different parts of the body to move. When the muscles contract, they shorten in length, which moves the body. When the contracted muscle cell relaxes, it regains its original length, bringing the body part back to its original position.  Muscle cells are also known as myocytes or muscle fibers because of their long shape that resembles fibers.