Red light therapy before exercise may help endurance in some activities but not others

A 2022 systematic review and meta-analysis pooled data from 37 placebo-controlled, double-blind crossover trials involving 586 healthy young adults to evaluate whether photobiomodulation therapy applied before exercise improves performance across different movement types. The results were mixed: modest benefits appeared for muscle endurance in isolated single-joint tasks and for time-to-exhaustion in cycling, while strength, running, and swimming outcomes showed no meaningful effect.

What the study found

The review found that photobiomodulation therapy was associated with a small but statistically significant improvement in muscle endurance during single-joint exercises — the kind of isolated, repetitive-contraction tasks common in laboratory settings — with a standardized mean difference of 0.27. However, it produced no detectable effect on muscle strength in those same exercise types.

For cycling, the therapy was associated with a similarly small improvement in time-to-exhaustion performance (SMD 0.35), suggesting a modest capacity to extend sustained effort. All-out sprint cycling, by contrast, showed no benefit.

Across running modalities — including time-to-exhaustion, time-trial, and repeated-sprint formats — no significant effects were found. Swimming time-trial performance was likewise unaffected. The authors are careful to frame these as mode-specific findings rather than a general verdict on the therapy.

The effect sizes where benefits did appear are small by conventional standards, meaning the practical significance for any individual exerciser remains uncertain. The pattern of results suggests the therapy may interact differently with aerobic endurance mechanisms than with maximal power or sport-specific locomotion.

Limits worth knowing

All included participants were healthy young adults, so findings cannot be generalized to older individuals, recreational exercisers, or clinical populations. The 37 trials varied in how they applied the therapy, making direct comparison across studies imperfect despite the crossover design requirement. The search cutoff of May 2022 means more recent work is not captured. Funding sources for individual included trials were not discussed in the abstract, and it is unclear whether any industry support influenced the underlying studies. The meta-analysis also could not fully account for differences in outcome measurement tools across labs.

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