Electrical stimulation uses an electrical current to cause a single muscle or a group of muscles to contract. By placing electrodes on the skin in various locations the physical therapist can recruit the appropriate muscle fibers. Contracting the muscle via electrical stimulation helps strengthen the affected muscle. The physical therapist can change the current setting to allow for a forceful or gentle muscle contraction. Along with increasing muscle strength, the contraction of the muscle also promotes blood supply to the area that assists in healing. Electrical stimulation can also be known as a TENS unit.