What the research says about EMS training

Whole-body electromyostimulation (WB-EMS) has accumulated a fair body of research over the past fifteen years — enough that guessing is no longer necessary. What follows is a review of what has actually been measured, including the areas where studies contradict each other.

Every figure below was checked against the original publication. Where results are not consistent, both are reported.

Muscle mass and strength: the strongest evidence

A 2021 systematic review and meta-analysis pooled 16 studies with 897 participants — 565 in EMS groups and 332 in controls. In non-athletic adults it found large, statistically significant effects on muscle mass and on leg and trunk strength [1].

Strength effects were similarly convincing: SMD 0.98 for leg strength (95% CI 0.74–1.22) and 1.08 for trunk strength (95% CI 0.78–1.39), both at p < 0.001. The authors also reported no significant heterogeneity between trials — the individual studies broadly agreed with one another [1].

Body fat: where the research conflicts

Honesty matters more here than effective advertising. The 2021 meta-analysis found no statistically significant effect on total fat mass — SMD −0.40 (95% CI −0.98 to 0.17), p = 0.170 [1]. The authors explicitly concluded that effects were large for muscle mass and strength, but not for fat mass.

A larger 2023 meta-analysis covering 26 studies with 1,183 participants did find a significant effect on body fat: SMD −0.38 (95% CI −0.62 to −0.15) [2]. That is a small-to-moderate effect, not a dramatic one.

The likeliest explanation for the mismatch is not that one of them got it wrong. Both found an effect of similar magnitude — they differ in whether it cleared the threshold of statistical significance, which with fewer pooled studies is often a question of statistical power. The practical conclusion is a modest one: EMS may contribute somewhat to fat reduction, but nutrition remains the main lever.

Can 20 minutes really make a difference?

A 2016 randomised controlled study tested this directly. Forty-eight untrained men aged 30–50 were randomly allocated either to high-intensity resistance training (twice a week) or to EMS (three 20-minute sessions per fortnight), over 16 weeks [3].

Lean body mass rose significantly in both groups (resistance 1.25%, EMS 0.93%; p = 0.001), with no significant difference between them (p = 0.395). Leg-extensor strength followed the same pattern: both groups improved, with no between-group difference (p = 0.215) [3].

Body recomposition is not the same as weight loss

Reshaping your body is not necessarily about a lower number on the scale; it is about a changed ratio between muscle and fat mass. More muscle alongside less fat can mean almost unchanged weight and a visibly different physique.

That is also why the evidence for EMS reads better than it first appears: it is strongest precisely for muscle mass and strength — the things that actually change body composition.

Preserving muscle while dieting

In a calorie deficit the body loses muscle alongside fat, so whether EMS prevents that is a worthwhile question.

A 16-week study of 90 overweight women measured lean body mass during energy restriction. It fell by 113 g in the control group and by 391 g in the physical-activity group, while the EMS group gained an average of 387 g. The overall analysis did not clear the significance threshold (p = 0.070), though the EMS-versus-activity comparison was borderline significant (p = 0.049). The authors concluded that EMS is an efficient, joint-friendly option for maintaining muscle mass during energy restriction [4].

A 2020 pilot study followed 29 women with obesity and metabolic syndrome for 12 weeks, comparing EMS twice weekly for 20 minutes alongside nutritional counselling against counselling alone. Body weight fell significantly in both groups, but body fat percentage fell only in the EMS group. Only the EMS group significantly increased maximum strength across all major muscle groups and improved its overall cardiometabolic risk score [5].

The same caveat applies to both studies: the samples were small and the findings are not conclusive — the first study's overall analysis did not clear the significance threshold. That is why we do not present EMS at Forma X as a better replacement for everything else, but as a form of training that is easier to do consistently when time is short — and consistency is what actually decides the outcome for most people.

What this means for you

EMS is not a shortcut around basic physiology. It is a tool that delivers a strong muscular stimulus for a relatively small time investment. Alongside adequate nutrition, sufficient protein, recovery and regularity, it can support:

• —increasing or maintaining muscle mass,
• —increasing muscular strength,
• —improving body composition,
• —training effectively when time is scarce,
• —lower mechanical joint loading than some forms of conventional training.