Electrical Muscle Stimulation (EMS), also known as Neuromuscular Electrical Stimulation (NMES) involves the use of electrical impulses to stimulate muscular contraction. The impulses are generated by an electrical device and delivered through electrodes placed directly on the skin over the muscle group(s) to be stimulated. Specific protocols can utilized to elicit different training responses such as recovery treatment, muscular endurance, muscular hypertrophy, muscular strength, or increase force production. For example, high-frequency currents are used for enhancing maximal strength, whereas low-frequency currents are used to develop endurance (Filipovic 2012).
Contraindications and warnings include no use with 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.
EMS is different from transcutaneous electrical nerve stimulation (TENS), in which an electric current is used for pain therapy.
The FDA (2013) asserts that muscle stimulators are misbranded when any of the following claims are made: girth reduction, loss of inches, weight reduction, cellulite removal, bust development, body shaping and contouring, and spot reducing.
Porcari (2002) found EMS, performed 3 times per week following the manufacturer's recommendations, had no effect on body composition, muscular strength, and physical appearance in college age volunteers.
EMS treatment has shown to be effective in rehabilitation under supervision of an authorized practitioner for the following uses:
- Prevention or retardation of muscular disuse atrophy
- When a voluntary training program is not possible due to injury or disability
- Increasing local blood circulation
- Muscle re-education
- Relaxation of muscle spasms
- Immediate post-surgical stimulation of calf muscles to prevent venous thrombosis
- Maintaining or increasing range of motion.
EMS has been used in former Communist Bloc countries for sport training since the early 1950s. Many coaches now use EMS as part of a training program for their athletes. The late track coach Charlie Francis used EMS as part of his training program for his Olympic-level athletes (Francis 2001).
The efficacy of the EMG treatment for sport training has been debated particularly because early studies using flawed protocols failed to show the true potential of EMG training when combined with traditional training techniques (Francis 2001).
According to Francis (2001), uses for EMS in sport training include:
- Enhancement of maximum strength
- Modality to enhance recovery
- Rehabilitation tool
- Motor learning and muscle recruitment tool
Gorndin (2011) reported EMS:
- Cannot effectively replace traditional resistance training
- May augment muscle function only if performed by certain protocols (eg: intensity, pulse duration, etc).
- May improve dynamic strength, motor performance skills and explosive movements (i.e., jump performance, sprint ability) when EMS training is combined with voluntary dynamic exercise like plyometrics and/or weight training.
Filipovic (2012) review of the scientific literature revealed EMS is effective for developing physical performance in trained an elite athletes. Significant gains were reported with stimulation period of 3-6 weeks:
- Maximal strength
- isometric Fmax +58.8%
- dynamic Fmax +79.5%
- Speed strength
- Eccentric isokinetic Mmax +37.1%
- Concentric isokinetic Mmax + 41.3%
- Rate of force development + 74%
- Force impulse + 29%; vmax + 19%
- Power +67%
Developing these parameters increases vertical jump height by up to +25% and improves sprint times by as much as -4.8% in trained and elite athletes.
Finberg (2013) reported that a single EMS recovery treatment resulted in improved sprint times during the 24-h post recovery, which was as effective for recovery as cold water treatment.
Bentio-Martinez (2013) found that EMS applied during plyometrics training and applying EMS prior to plyometrics training significantly improved triple jump performance. Incidentally, applying EMS after plyometric training provided no significant improvements. Electrostimulation parameters involved 150 Hz frequency, 350 Hz pulse width, 3-12 second contraction rest time, 2 days / week, 12 minutes / dosage, 36 contractions / session, at maximum athlete-tolerated intensity varying between 60 and 130 mA.
Francis (2001) recommends 10 sec contractions time for sprinters and 6 second contraction time for shot putters and linemen. In both cases, a 50 second rest period is suggested. The shortest ramp up time (0 to max intensity) that the athlete can tolerate should be chosen. For large muscle group, Ideally four pads are applied. Since EMS contraction is strongest around the negative electrode, place the negative pad over the largest bulk of the muscle to keep the contraction even throughout the muscle.
10 to 15 treatments can be used to maximize recruitment velocity. However, most off the strength benefits can be achieved within 10 treatments. The number of treatments that can be administered before reaching a maximal strength gain plateau may vary between 15 (2.5 - 4 weeks) to 25 treatments (4-7 weeks). (Francis 2001)
Francis (2001) explains:
"A quadrennial plan for a top sprinter might include EMS strength building twice per year during years one and two, reducing to once during year three and only if needed in year four."
Both trained and elite athletes, despite their already high level of fitness, are able to significantly enhance their level of strength to same extent as is possible with untrained subjects (Filipovic 2012).
EMS in Sports Conditioning
Francis C (2001), The Truth About EMS -Electronic Muscle Stimulation: Facts and Fallacies. T-Nation.com
Porcari JP, McLean KP, Foster C, Kernozek T, Crenshaw B, Swenson Chad. Effects of Electrical Muscle Stimulation on Body Composition, Muscle Strength, and Physical Appearance. Journal of Strength and Conditioning Research, 16(2): 165-172. 2002.
Benito-Martínez, Martínez-Amat A, Lara-Sánchez AJ, Berdejo-Del-Fresno D, Martínez-López EJ. (2013). Effect of combined electrostimulation and plyometric training on 30 meters dash and triple jump. J Sports Med Phys Fitness. 53(4):387-95.
FDA (2013) Import Alert Import Alert 89-01.
Finberg M1, Braham R, Goodman C, Gregory P, Peeling P. (2012). Effects of electrostimulation therapy on recovery from acute team-sport activity. Int J Sports Physiol Perform. 8(3):293-9.
Filipovic A1, Kleinöder H, Dörmann U, Mester J. (2012). Electromyostimulation--a systematic review of the effects of different electromyostimulation methods on selected strength parameters in trained and elite athletes. J Strength Cond Res. 26(9):2600-14.
Gondin J, Cozzone PJ, Bendahan D (2011). Is high-frequency neuromuscular electrical stimulation a suitable tool for muscle performance improvement in both healthy humans and athletes? European Journal of Applied Physiology. 111(10): 2473-2487 .