Electrical muscle stimulation (EMS), also known as neuromuscular electrical stimulation (NMES) or electromyostimulation, is the elicitation of muscle contraction using electric impulses. The impulses are generated by a device and delivered through electrodes on the skin in direct proximity to the muscles to be stimulated. The impulses mimic the action potential coming from the central nervous system, causing the muscles to contract. The electrodes are generally pads that adhere to the skin. EMS is both a form of electrotherapy and of muscle training. It is cited by important authors as complementary technique for sport training, and there is published research on the results obtained. In the United States, EMS devices are regulated by the U.S. Food and Drug Administration (FDA).
Luigi Galvani (1791) provided the first scientific evidence that current can activate muscle. During the 19th and 20th century researchers studied and documented the exact electrical properties that generate muscle movement.It was discovered that the body functions induced by electrical stimulation caused long-term changes in the muscles.In the '60s Soviet sport scientists applied EMS in the training of elite athletes, claiming 40% force gains.In the '70s these studies were shared during conferences with the Western sport establishments. However, results were conflicting, perhaps because the mechanisms in which EMS acted was poorly understood. Recent medical physiology research pinpointed the mechanisms by which electrical stimulation causes adaptation of cells of muscles, blood vessels and nerves.
EMS causes adaptation, i.e. training, of muscle fibers. Because of the characteristics of skeletal muscle fibers, different types of fibers can be activated to differing degrees by different types of EMS, and the modifications induced depend on the pattern of EMS activity. These patterns, referred to as protocols or programs, will cause a different response from contraction of different fiber types. Some programs will improve fatigue resistance, i.e. endurance, others will increase force production.
EMS can be used both as a training and a therapeutic tool.
In medicine EMS is used for rehabilitation purposes, for instance in the prevention of disuse muscle atrophy which can occur for example after musculoskeletal injuries, such as damage to bones, joints, muscles, ligaments and tendons. However, this should not be confused with TENS (Transcutaneous Electrical Nerve Stimulator): the use of electric current in pain therapy.
