The short version: the muscle contracts because an impulse tells it to
A muscle contracts when an electrical signal reaches it along a nerve. Electrical muscle stimulation reproduces that signal — except it comes from a device through electrodes resting on the skin rather than from your brain. The resulting contraction is the same kind of event as one you generate yourself.
In whole-body EMS (WB-EMS in the research literature), the electrodes are sewn into a suit so they cover most major muscle groups simultaneously: thighs, glutes, abdominals, chest, back and arms. During the session you perform ordinary exercises — squats, lunges, arm movements — while the impulse runs underneath and deepens each contraction.
What the research shows
EMS is not new — physiotherapy has used various forms of it for decades. What is more recent is whole-body application in healthy, untrained adults, and that is where most of the last decade's research sits.
A 2018 systematic review gathered studies on low-frequency WB-EMS in non-athletic adults and concluded that the technology has a positive effect on health-related outcomes, particularly muscle mass and body composition — provided it is applied correctly and under supervision [1].
A 2021 meta-analysis pooling several controlled trials in non-athletic adults confirmed statistically significant effects of WB-EMS on body composition and muscle strength [2]. One caveat the authors stress: individual study samples are relatively small and protocols vary, so the results should be read as promising rather than settled.
„EMS isn't a shortcut around effort. It's a way to do in 20 minutes work that would otherwise be spread across a much longer session — which is exactly why it makes sense for people who genuinely don't have the time."
What a session looks like
- 1.You put on the EMS suit; your trainer fits it to your body so the electrodes make good contact.
- 2.A short familiarisation phase follows, raising the intensity gradually to a level that is demanding but manageable.
- 3.For roughly 20 minutes you perform trainer-led exercises while the impulse cycles between load and rest.
- 4.The session ends with recovery — at Forma X, electro-massage and a protein shake.
Intensity is set separately for each muscle group, usually on a 0–100 scale. At Forma X most people find 30 to 40 a comfortable working range, but this is highly individual and shifts over the weeks.
How often — and why beginners get a different answer
At Forma X most clients train twice a week — one harder session and one lighter one, with enough recovery in between. Intensity starts lower and builds gradually as the body adapts to the load.
The reason is not caution for its own sake. Whole-body stimulation produces an unusually large muscular load in a short time, and starting too aggressively raises the risk of excessive muscle breakdown. Gradual progression removes that risk almost entirely.
Who EMS is not suitable for
Whole-body EMS has clear contraindications. They include pregnancy, cardiac conditions and implanted pacemakers, epilepsy, metal implants in the stimulated area, acute inflammation, and broken skin where the electrodes sit. With any chronic condition, consult a doctor before starting.
A full breakdown of contraindications and safety rules
Safety and contraindicationsDoes EMS replace conventional training?
Partly. For optimal fitness and overall physical health we recommend adding regular cardio, stretching and training with heavier loads. You can fit all of that in with us too (the COMBO package) — ask your trainer what she would suggest for you.
Sources
Claims about the effects of electrical muscle stimulation on this page are based on the peer-reviewed publications listed below.
- [1]Kemmler W, Weissenfels A, Willert S, et al. (2018). Efficacy and Safety of Low Frequency Whole-Body Electromyostimulation (WB-EMS) to Improve Health-Related Outcomes in Non-athletic Adults. A Systematic Review. Frontiers in Physiology, 9:573. doi:10.3389/fphys.2018.00573
- [2]Pano-Rodriguez A, Beltran-Garrido JV, Hernández-González V, Reverter-Masia J. (2021). Efficacy of Whole-Body Electromyostimulation (WB-EMS) on Body Composition and Muscle Strength in Non-athletic Adults. A Systematic Review and Meta-Analysis. Frontiers in Physiology, 12:640657. doi:10.3389/fphys.2021.640657
Content is written and reviewed by the Forma X team. This article is not a substitute for medical advice.