Electrical muscle stimulation

Athlete squatting with four-channel, electrical muscle stimulation machine for training, attached through self-adhesive pads to her quadriceps.

Electrical muscle stimulation (EMS), also known as neuromuscular electrical stimulation (NMES) or electromyostimulation, is the elicitation of muscle contraction using electric impulses. EMS has received increasing attention in the last few years because of its potential to serve as a strength training tool for healthy subjects and athletes, a rehabilitation and preventive tool for partially or totally immobilized patients, a testing tool for evaluating the neural and/or muscular function in vivo, and a post-exercise recovery tool for athletes.^[1] 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. The use of EMS has been cited by sports scientists^[2] as a complementary technique for sports training and published research is available on the results obtained.^[3] In the United States, EMS devices are regulated by the U.S. Food and Drug Administration (FDA).^[4]

The XVIII Congress of the International Society of Electrophysiology and Kinesiology (ISEK 2010), which took place in Aalborg, Denmark on 16–19 June 2010, had a dedicated session on the subject: Electrical stimulation for testing and training in exercise and sports. As part of it, numerous research papers and reviews have been published.^[5][6]

History

Luigi Galvani (1791) provided the first scientific evidence that current can activate muscle. During the 19th and 20th centuries, researchers studied and documented the exact electrical properties that generate muscle movement.^[7][8] It was discovered that the body functions induced by electrical stimulation caused long-term changes in the muscles.^[9][10] In the 1960s, Soviet sport scientists applied EMS in the training of elite athletes, claiming 40% force gains.^[11] In the 1970s, these studies were shared during conferences with the Western sport establishments. However, results were conflicting, perhaps because the mechanisms in which EMS acted were poorly understood.^[12] Recent medical physiology research^[13][14] pinpointed the mechanisms by which electrical stimulation causes adaptation of cells of muscles, blood vessels^[15][16][17] and nerves.^[18]

Effects

"Strength training by NMES does promote neural and muscular adaptations that are complementary to the well-known effects of voluntary resistance training".^[1] This statement is part of the editorial summary of a 2010 world congress of researchers on the subject. Additional studies on practical applications, which came after that congress, pointed out important factors that make the difference between effective and ineffective EMS.^[19][20] This in retrospect explains why in the past some researchers and practitioners obtained results that others could not reproduce. Also, as published by reputable universities, EMS causes adaptation, i.e. training, of muscle fibers.^[21] Because of the characteristics of skeletal muscle fibers, different types of fibers^[22] can be activated to differing degrees by different types of EMS, and the modifications induced depend on the pattern of EMS activity.^[14] 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.^[18]

Use

EMS can be used as a training,^[23][24][25] therapeutic,^[26][27] and cosmetic tool. In medicine, EMS is used for rehabilitation purposes, for instance in physical therapy 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. This is distinct from transcutaneous electrical nerve stimulation (TENS), in which an electric current is used for pain therapy.

Because of the effect that strengthened and Hypertrophied muscles have on appearance (a stronger muscle has larger cross-section^[28]), EMS is also used by a niche of practitioners for aesthetics goals.^[29][30][31] The FDA rejects certification of devices that claim weight reduction.^[32] EMS devices cause a calorie burning that is marginal at best: calories are burnt in significant amount only when most of the body is involved in physical exercise: several muscles, the heart and the respiratory system are all engaged at once.^[33] However, some authors imply that EMS can lead to exercise, since a person toning his/her muscles with electrical stimulation is more likely afterwards to participate in sporting activities as the body is ready, fit, willing and able to take on physical activity.^[34] In EMS training few muscular groups are targeted at the same time, for specific training goals.^[34] The effectiveness of the devices for sport training has been debated. A number of coaches regularly use professional EMS devices as an integral part of the training of their athletes; some of these are high profile coaches, such as track coach Charlie Francis, who used the technique to supplement the training of Olympic-level athletes.^[35]

Non-professional devices target home-market consumers^[36] with wearable units in which EMS circuitry is contained in belt-like garments (ab toning belts) or other clothing items.

FDA certification in USA

The U.S. Food and Drug Administration (FDA) certifies and releases EMS devices into two broad categories: over-the counter devices (OTC), and prescription devices. OTC devices are marketable only for muscle toning; prescription devices can be purchased only with a medical prescription for therapy. Prescription devices should be used under supervision of an authorized practitioner, for the following uses:

• Relaxation of muscle spasms;
• Prevention or retardation of disuse atrophy;
• Increasing local blood circulation;
• Muscle re-education;
• Immediate post-surgical stimulation of calf muscles to prevent venous thrombosis;
• Maintaining or increasing range of motion.

The FDA mandates that manuals prominently display contraindication, warnings, precautions and adverse reactions, including: no use for wearer of pacemaker; no use on vital parts, such as carotid sinus nerves, across the chest, or across the brain; caution in the use during pregnancy, menstruation, and other particular conditions that may be affected by muscle contractions; potential adverse effects include skin irritations and burns

Only FDA-certified devices can be lawfully sold in the US without medical prescription. These can be found at the corresponding FDA webpage for certified devices.^[37] The FTC has cracked down on consumer EMS devices that made unsubstantiated claims;^[38] many have been removed from the market, some have obtained FDA certification.

Popular culture

• The 1996 Star Wars novel Shadows of the Empire describes a 'myostim' chair that artificially stimulates muscles to build muscle mass and strength.
• The science fiction movie The Matrix contains a scene in which Neo's muscles are activated by means of acupuncture needles and EMS after being 'cocooned' for a long time aboard ship Nebuchadnezzar.
• In a documentary about Bruce Lee one of his friend states in an interview that Bruce Lee used electrical wires to increase his muscle development.

See also

• Electrotherapy
• Electrotherapy (cosmetic)
• Skeletal muscle
• Musculoskeletal injury
• Scoliosis
• Locked-in syndrome

References

Further reading

• Maffiuletti, Nicola A (December 2006). "The use of electrostimulation exercise in competitive sport" (PDF). International Journal of Sports Physiology and Performance 1 (4): 406–7. ISSN 1555-0265. PMID 19124897. Retrieved 2014-06-13. 
• Maffiuletti, Nicola A; Marco A Minetto; Dario Farina; Roberto Bottinelli (October 2011). "Electrical stimulation for neuromuscular testing and training: state-of-the art and unresolved issues" (PDF). European Journal of Applied Physiology 111 (10): 2391–2397. doi:10.1007/s00421-011-2133-7. ISSN 1439-6327. PMID 21866361. Retrieved 2014-06-13. 
• Boschetti, Gianpaolo (2008). Globus SHT, ed. "EMS Digest". Retrieved 2013-01-29.  Google document inspired by a workshop by author Gianpaolo Boschetti (2000). Che cos'è l'elettrostimolazione. Libreria dello Sport. Retrieved 2013-01-10.  It is compiled to serve as a practical guide to understanding electrical muscle stimulation for sport training, and is supplemented by material taught by the author during workshops, and by appendices written by professional trainers.

External links

• Collection of Extensive Bibliography and Abstracts
• Seattle Times - opinion piece on personal electronic muscle stimulation belts
• John Porcari @ University of Wisconsin–La Crosse next plans to study ems buttocks and thigh toners
• CBC News. Virtual exercise machine could speed recovery. May 14, 2014.