Adding red light therapy to resistance training did not raise 1RM

Red light panels and laser devices are sold on the promise of accelerating strength gains. This meta-analysis tested that promise against a single hard outcome — the one-rep max — and the answer was negative. An effect size of 0.26 with an interval crossing zero is not an effect you can claim.

What was analysed?

Seven databases were searched to January 2026 for randomised trials combining photobiomodulation, delivered by low-level laser or LED, with resistance training or other strength-oriented loading tasks. That yielded 11 trials in 456 people. Only the five that paired it with periodized resistance training and reported 1RM entered the pooled analysis; the rest were synthesised narratively. That restriction was prespecified.

"No effect shown" is not "no effect exists"

The paper's own wording is that current evidence does not demonstrate a clear additional benefit, while noting that a small effect cannot be excluded — the pooled analysis rested on 146 people across both arms. Heterogeneity was low, however (I² = 4%), so there was no between-study scatter suggesting a hidden reversal.

So is it useless?

For building strength, it has no support. Outside resistance training contexts — in frail or critically ill older adults — some studies reported benefits for fatigue, recovery and function-related outcomes, but the findings were inconsistent. And since this analysis studied older adults throughout, it is not data you can transfer directly to a young trained lifter.

Where the money and the time should go

One question sorts recovery gadgets quickly: has it been tested against the outcome you care about? Red light has been tested against 1RM, and it did not pass. The variables that do move strength outcomes repeatedly are far more boring: sleep, total protein intake, weekly set count. Those are covered in sleep loss and lifting performance and how many rest days you need. Fixing those three first has a better expected return than any device.