Electrical stimulation while you lift nudges gains a little higher

Neuromuscular electrical stimulation, where electrodes on the skin make a muscle contract, has long been used in rehabilitation. A newer idea is to run that stimulation at the same time as ordinary resistance training, on the theory that the combined contraction works the muscle harder than lifting alone. Whether that actually translates into more strength and more muscle than conventional training has been unclear, with individual trials pointing in different directions. This review set out to test whether the combination genuinely has an additive effect over lifting by itself.

The researchers searched EBSCO, Google Scholar, PubMed and ResearchGate for randomised controlled trials that directly compared resistance training on its own against resistance training performed simultaneously with neuromuscular electrical stimulation. Thirteen studies met the inclusion criteria. For each outcome, strength gain and muscle mass, the team calculated standardised mean differences, a way of putting results measured on different scales onto one common footing. These were then pooled using random effects models, which allow for genuine differences between the included studies.

Adding stimulation to lifting came out ahead on both counts. For strength, the pooled effect favoured the combined approach with a standardised mean difference of 0.31, a small to moderate advantage. For muscle mass the advantage was similar at 0.26, and both results were statistically significant. One note of caution sits in the strength result: the individual trials disagreed with each other quite substantially, which makes the exact size of the strength benefit harder to pin down, whereas the muscle mass findings were far more consistent across studies.

This pooled analysis strengthens the case that superimposed stimulation is more than a gimmick, moving the question on from single conflicting trials to a consistent overall signal. The effects, however, are modest rather than transformative, and the review does not address who benefits most, which stimulation settings work best, or how long the advantage lasts. The authors themselves flag the next frontier: whether combining stimulation with training also improves metabolic or cardiovascular health, something no study here measured.

For someone already lifting, this is a reason to think electrical stimulation layered onto training can add a small extra return in strength and size, rather than being a replacement for the work itself. The advantage was modest, so conventional progressive training remains the foundation of the results seen here. It is also worth knowing that the evidence covers stimulation used during lifts, not devices used passively while resting, which this review did not test.