Key Points
- EMS can aid recovery from injury and surgery and facilitate improvements in strength, hypertrophy, muscular endurance, and possibly movement performance
- EMS is best used as an addition to regular training except for performance benefits
- Optimally, the ‘intensity’ of contraction should be higher (at or near tolerable doses) for hypertrophy and strength and adjusted to allow for greater time under tension (appropriate to the demands of your sport) for muscular endurance and recovery
- EMS should be used relatively frequently for best results (i.e. > 3 x per week)
EMS or electrical muscle stimulation (also, neuromuscular electrical stimulation or electromyostimulation) involves using a device to contract a muscle using electric impulses.
EMS is known to improve isometric maximal strength in athletes and people who exercise and this effect might be most pronounced in those aged ~20-22.1 Recreational athletes also receive significant benefits with EMS training, resulting in improved strength and overall physical functioning.2, 3 However, more functional outcomes like dynamic strength, complex motor performance and explosive movements are typically obtained when EMS is used in conjunction with specific training. So, for athletes, EMS can be used alone post-injury for the improvement of strength, range of motion, and endurance, and for performance improvements, can provide additional benefits when added to regular training.4
[Also: check out articles on TENS and Microcurrent therapies]
Athletic applications
Maintenance and improvement of strength and mobility post-surgery
In athletes and healthy people, EMS has been shown to improve strength and reduce decrements in strength as a result of immobility after surgery. A systematic review by Dai Wen-min and colleagues concluded that EMS can improve muscle strength, increase range of motion, reduce oedema, reduce muscle atrophy, promote tissue healing and relieve pain after anterior cruciate ligament surgery.5
Studies have demonstrated increased strength (vs control) in quadriceps strength after anterior cruciate ligament surgery,6 and muscle activation and both quadriceps and hamstring strength and knee extension range of motion after total knee arthroplasty.7-9 Review of the evidence also suggests that the effect of EMS combined with exercise is more effective than exercise alone.10
In a study of competitive soccer players undergoing an exercise and rehabilitation program following ACL reconstruction, there was an approximately 10-fold increase in strength for those using EMS+exercise compared to the control group (exercise only). Those using EMS also had significant increases in quadriceps size when compared to the Ex-only group.11
These results have also been replicated in closed-chain exercise (single leg squat and lateral step-up) with performance significantly improved for rehabilitation exercise + EMS compared with exercise alone.12
Improved neuromuscular performance
In the athletic realm, EMS is commonly used to facilitate performance by combining treatment with voluntary contraction of the muscle, weight training, or complex movements. These adaptations are not confined to the activated muscle but also involve neural adaptations through reflex inputs to the spinal cord.13
In one study of Russian wrestlers, stimulation of muscles like the gluteus maximus and latissimus dorsi during the execution of throwing movements improved activation and performance.14 There may also be equivalent benefits between a standard and EMS warm-up before strength activities.15
Improvements in strength
Use of an EMS device on the abdominals for 5 days per week over 8 weeks resulted in increases in abdominal strength of 58% and 100% increase in abdominal endurance. The control group doing no abdominal exercise had no increases in strength and only a 28% increase in abdominal endurance. Additionally, those using the EMS reduced waist circumference by 3.5 cm without any significant loss of weight or body fat,16 suggesting that the decrease in waist circumference was due to improved muscle activation.
In a later study by the same research team, significant improvements in strength and endurance were seen from using high-intensity EMS but not from low-intensity (which could be felt but did not elicit a muscular contraction).17 However, a nearly identical study reported no significant differences between the high and low-intensity application of EMS after 6 weeks (5 days per week).18
In another study of healthy, young men, 12 weeks of EMS training of one bicep resulted in a significant increase in elbow flexion torque (23% increase), and muscle thickness (8-16%).19 However, in an exercise vs EMS study on knee extension strength, no difference was observed between exercise and exercise + EMS.20
In a functional study in healthy college-age athletes, significant improvements in both calf strength and power were observed in those using EMS (100 minutes over 4 weeks with visible strong contractions) compared to doing 100 minutes of plyometric training (box jumps and depth jumps) over the same time-frame.21
Hypertrophy
Research has demonstrated increases in muscle thickness of the bicep19 from EMS training, however, other research has shown no significant effect (although there was a trend towards improvement).22 Interestingly, in both healthy young and older people, a ‘hybrid’ method of training using EMS along with voluntarily contracting the muscle, has been shown to be as effective as weight-machine training for increasing muscle size (and strength).23
Improvements in power
In a study looking at vertical jump performance (a standard measure of weight-dependent power) groups using an 80 Hz current for 15 min and 25 Hz for 60 min had improved jump height (by 5 and 3 cm respectively) after one week compared to a control group. These results were maintained following five weeks of EMS training.24
This study is interesting in that a lower current designed to improve endurance also had a crossover to power, and because the study was performed in young, healthy, trained males.
Improvements in muscular endurance
Both low (~10 Hz) and high (up to 50Hz) EMS results in improvements in muscular endurance in healthy subjects. However, the benefits are greatest for low-frequency EMS, likely due to the ability to repeat sessions and use for longer durations.25
https://www.frontiersin.org/articles/10.3389/fphys.2016.00544/full
When added to a high-intensity interval training program (HIIT) (12 seconds on, 8 seconds off, 45–60 Hz, 300 µs, Wave: Square 274) EMS resulted in significant improvements in V02max, lactate concentration, and time to exhaustion.26
Facilitating recovery
EMS has been demonstrated to be as effective as active recovery exercise and ischemic preconditioning for improving blood volume, lactate, and pH between two 5 km cycling time trials.27
Can you train agonist-antagonist muscles together?
It appears that there is no difference in peak torque and activation when isolating a muscle compared to activating the agonist-antagonist pairing (i.e. quadriceps and hamstrings).28
Is there crossover between limbs?
In a study looking at whether bilateral improvements occurred from unilateral stimulation, EMS treatment of the left thenar muscle (in the palm) resulted in significant improvements in hypertrophy and strength of the left hand and a trend towards improvements in the right (non-stimulated) hand.29
How often?
A study compared the use of EMS for the maximal voluntary contraction of the quadriceps zero, two, and three times per week (10 min per session). Only the group receiving three treatments per week had significant improvements in strength.30
This suggests that devices should be used three or more times per week for the greatest benefits.
How strong?
The benefits for strength and hypertrophy likely rely on relatively high ‘intensity’ of muscle contraction. For example, in a study comparing EMS at approximately 20% of the maximal voluntary contraction, no difference was seen between EMS and no training.31 However, relatively low intensity of contraction has resulted in improvements in endurance and crossover to power,24 and when the intensity allows for greater times under tension, this has a better crossover to endurance.25
Summary
While there have been some equivocal findings, taken as a whole the evidence shows that EMS can improve recovery from injury and surgery, strength, power, muscle mass, and some key aspects of crossover performance including facilitating muscle activation and complex skill performance and increasing time-to-exhaustion. While there is benefit from using EMS alone, especially in sedentary people, the benefits are greatest when combining EMS with voluntary contraction of the muscle. This can take the form of actively contracting the muscle without external load, or preferably for athletes to use EMS in addition to, or concurrently with ‘best-practice’ training for the desired outcome.
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References
1. Xiao H, Yifan L, Jingmin L. Meta-analysis of muscle strength of exercisers undergoing electrical muscle stimulation training. Chinese Journal of Tissue Engineering Research. 2020;24(23):3764.
2. Caulfield B, Prendergast A, Rainsford G, Minogue C, editors. Self directed home based electrical muscle stimulation training improves exercise tolerance and strength in healthy elderly. 2013 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC); 2013 3-7 July 2013.
3. Banerjee P, Caulfield B, Crowe L, Clark A. Prolonged electrical muscle stimulation exercise improves strength and aerobic capacity in healthy sedentary adults. Journal of Applied Physiology. 2005;99(6):2307-11.
4. Gondin J, Cozzone PJ, Bendahan D. Is high-frequency neuromuscular electrical stimulation a suitable tool for muscle performance improvement in both healthy humans and athletes? European Journal of Applied Physiology. 2011;111(10):2473.
5. Dai Wen-min DJ, Zhou Wen, Xu Lin-lin, Li Fang-xiang. Effects of neuromuscular electrical stimulation on muscle strength after anterior cruciate ligament reconstruction. Chinese Journal of Tissue Engineering Research. 2015;19(7):1082-6.
6. Fitzgerald GK, Piva SR, Irrgang JJ. A Modified Neuromuscular Electrical Stimulation Protocol for Quadriceps Strength Training Following Anterior Cruciate Ligament Reconstruction. Journal of Orthopaedic & Sports Physical Therapy. 2003;33(9):492-501.
7. Stevens-Lapsley JE, Balter JE, Wolfe P, Eckhoff DG, Kohrt WM. Early neuromuscular electrical stimulation to improve quadriceps muscle strength after total knee arthroplasty: a randomized controlled trial. Physical therapy. 2012;92(2):210-26.
8. Stevens-Lapsley JE, Balter JE, Wolfe P, Eckhoff DG, Schwartz RS, Schenkman M, et al. Relationship Between Intensity of Quadriceps Muscle Neuromuscular Electrical Stimulation and Strength Recovery After Total Knee Arthroplasty. Physical Therapy. 2012;92(9):1187-96.
9. Petterson S, Snyder-Mackler L. The Use of Neuromuscular Electrical Stimulation to Improve Activation Deficits in a Patient With Chronic Quadriceps Strength Impairments Following Total Knee Arthroplasty. Journal of Orthopaedic & Sports Physical Therapy. 2006;36(9):678-85.
10. Kim K-M, Croy T, Hertel J, Saliba S. Effects of Neuromuscular Electrical Stimulation After Anterior Cruciate Ligament Reconstruction on Quadriceps Strength, Function, and Patient-Oriented Outcomes : A Systematic Review. Journal of Orthopaedic & Sports Physical Therapy. 2010;40(7):383-91.
11. Taradaj J, Halski T, Kucharzewski M, Walewicz K, Smykla A, Ozon M, et al. The Effect of NeuroMuscular Electrical Stimulation on Quadriceps Strength and Knee Function in Professional Soccer Players: Return to Sport after ACL Reconstruction. BioMed Research International. 2013;2013:802534.
12. Ross M. The effect of neuromuscular electrical stimulation during closed kinetic chain exercise on lower extremity performance following anterior cruciate ligament reconstruction. Sports Medicine, Training and Rehabilitation. 2000;9(4):239-51.
13. Vanderthommen M, Duchateau J. Electrical Stimulation as a Modality to Improve Performance of the Neuromuscular System. Exercise and Sport Sciences Reviews. 2007;35(4):180-5.
14. Podlivaev BA, Rozhin NN, Yakovlev BA. Improving the Performance of Throws in Freestyle Wrestling Using Electrical Muscle Stimulation. International Journal of Wrestling Science. 2014;4(1):5-19.
15. Ng JJW. Warming up using electrical muscle stimulation-does it increase strength and power? 2019.
16. Porcari JP, Miller J, Cornwell K, Foster C, Gibson M, McLean K, et al. The effects of neuromuscular electrical stimulation training on abdominal strength, endurance, and selected anthropometric measures. Journal of sports science & medicine. 2005;4(1):66-75.
17. Porcari J, Ryskey A, Foster C. The Effects of High Intensity Neuromuscular Electrical Stimulation on Abdominal Strength and Endurance, Core Strength, Abdominal Girth, and Perceived Body Shape and Satisfaction. 2018. 2018;6(1):7.
18. Olson JA. The effects of neuromuscular electrical stimulation on abdominal strength and endurance and core strength 2014.
19. Son J, Lee D, Kim Y. Effects of involuntary eccentric contraction training by neuromuscular electrical stimulation on the enhancement of muscle strength. Clinical Biomechanics. 2014;29(7):767-72.
20. Avila M, Brasileiro J, Salvini T. Electrical stimulation and isokinetic training: effects on strength and neuromuscular properties of healthy young adults. Brazilian Journal of Physical Therapy. 2008;12:435-40.
21. Barber N. The effects of electrical muscle stimulation on muscle strength, power, and size. 2012.
22. Pernambuco AP, Carvalho NMd, Santos AHd. A eletroestimulação pode ser considerada uma ferramenta válida para desenvolver hipertrofia muscular? Fisioterapia em Movimento. 2013;26:123-31.
23. Takano Y, Haneda Y, Maeda T, Sakai Y, Matsuse H, Kawaguchi T, et al. Increasing Muscle Strength and Mass of Thigh in Elderly People with the Hybrid-Training Method of Electrical Stimulation and Volitional Contraction. The Tohoku Journal of Experimental Medicine. 2010;221(1):77-85.
24. Paillard T, Noe F, Bernard N, Dupui P, Hazard C. Effects of Two Types of Neuromuscular Electrical Stimulation Training on Vertical Jump Performance. The Journal of Strength & Conditioning Research. 2008;22(4).
25. Veldman MP, Gondin J, Place N, Maffiuletti NA. Effects of neuromuscular electrical stimulation training on endurance performance. Frontiers in physiology. 2016;7:544.
26. Umutlu G, Demirci N, Acar NE. Training-induced changes in muscle contraction patterns enhance exercise performance after short-term neuromuscular electrical stimulation. Isokinetics and Exercise Science. 2020(Preprint):1-11.
27. Paradis-Deschênes P, Lapointe J, Joanisse DR, Billaut F. Similar Recovery of Maximal Cycling Performance after Ischemic Preconditioning, Neuromuscular Electrical Stimulation or Active Recovery in Endurance Athletes. Journal of Sports Science & Medicine. 2020;19(4):761.
28. Duignan C, Doolan M, Doyle D, McGowan J, O’Shaughnessy S, Minogue C, et al., editors. A performance comparison of neuromuscular electrical stimulation protocols for isolated quadriceps contraction versus co-contraction of quadriceps and hamstrings. 2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC); 2019 23-27 July 2019.
29. Jeong HS, Yeon KJ, Sik YT. Effects of Neuromuscular Electrical Stimulation on the Muscle Hypertrophy and Cross Training Effect. Ann Rehabil Med. 2006;30(6):655-60.
30. Parker MG, Bennett MJ, Hieb MA, Hollar AC, Roe AA. Strength Response in Human Quadriceps Femoris Muscle During 2 Neuromuscular Electrical Stimulation Programs. Journal of Orthopaedic & Sports Physical Therapy. 2003;33(12):719-26.
31. R Holcomb W. Effect of training with neuromuscular electrical stimulation on elbow flexion strength. Journal of sports science & medicine. 2006;5(2):276-81.
