Red light therapy shows small gains in muscle strength and endurance across 23 trials

A systematic review and meta-analysis pooled data from 23 randomized controlled trials to examine whether photobiomodulation therapy improves muscle strength and endurance in healthy people. Both outcomes showed statistically significant but small effects, and the authors caution that the evidence is not yet strong enough to draw firm conclusions about how the therapy should be applied.

What the study found

The meta-analysis found statistically significant but small improvements in both muscle endurance and muscle strength when photobiomodulation therapy was compared with placebo controls across the included trials. The effect sizes were modest, and the authors are careful to frame these as preliminary rather than definitive.

Subgroup analyses — which broke down results by participant type, device settings, timing, and number of treatment sites — were mostly nonsignificant. A potential endurance benefit appeared among athletes but not among physically active non-athletes, and even the athlete finding sat at the edge of conventional significance thresholds, making it exploratory at best.

The authors note that certain parameter combinations were associated with more favorable endurance or strength outcomes in subgroup analyses, but they explicitly describe these findings as insufficient to define any optimal approach. The pattern of results varied enough across studies that no single configuration emerged as clearly superior.

Overall, the review concludes that photobiomodulation therapy may offer modest support for muscle performance outcomes, with endurance-related measures showing slightly more consistent signals than strength. The authors call for larger, higher-quality trials with standardized methods before stronger claims can be made.

Limits worth knowing

The review included only 23 RCTs, and the individual trials varied considerably in participant characteristics, device parameters, and outcome measurement approaches, which limits the reliability of pooled estimates. The population was restricted to healthy humans, so findings do not extend to clinical or rehabilitative contexts. Subgroup analyses were exploratory and underpowered, meaning those results should be interpreted with caution. The search ran through November 2025, and no industry funding disclosures are noted in the abstract, though funding status across the 23 included trials is not detailed here. Methodological quality was assessed using the Cochrane Risk of Bias 2 tool, but the distribution of bias ratings across included studies is not summarized in the abstract.

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