An electric muscle stimulator (EMS) is a device that sends small pulses of electric energy through a muscle to cause contractions. These contractions may cause the muscle to strengthen, increase the muscle's mobility or promote blood flow. In most people, muscles tone and strength are developed through exercising the muscle physically. The process starts by the brain sending a signal through the spinal cord and to the nerves of the muscle. This signal tells the muscles to expand or contract. As the muscles continue to expand and contract, the tissue begins to break down. Once your body stops contracting the muscle, it will automatically start building the muscle tissue back up. The muscle will also make the tissue stronger to better face contractions in the future.

With neuromuscular electrical stimulation (NMES), instead of your brain sending a signal to your muscles through the spinal cord, the NMES machine electrically stimulates the nerves attached to the muscle at the motor point. Once the nerves are stimulated, they cause the muscle to expand and contract, much in the same way as conventional exercise. This allows those who are unable to exercise in the traditional manner to still gain greater strength and muscle mass.

NMES can be used for a variety of reasons including increasing blood circulation to the muscle, relaxing muscle spasms, prevention of muscle atrophy in patients unable to use parts of their body, prevention of venous thrombosis during or after surgery and increasing range of motion. Electrotherapy stimulates injured muscles and joints to activate the body's natural processes for relieving pain, building strength and promoting healing.