Red light therapy may ease fatigue recovery in healthy people but shows no strength or capacity gains

A 2023 systematic review with meta-analysis pooled 16 randomized controlled trials involving 340 healthy adults to evaluate whether photobiomodulation therapy (PBMT) improves strength, fatigue recovery, and functional capacity. Fatigue recovery showed a statistically significant improvement, but no meaningful benefit was detected for muscular strength or either short- or long-term functional capacity.

What the study found

The review found a statistically significant association between PBMT and improved fatigue recovery, with a mean difference of 5.87 (95% CI: 3.83–7.91) on the pooled measure. This was the only outcome where the evidence pointed in a consistent direction.

For muscular strength, results across three different measurement approaches — peak torque, one-repetition maximum, and isometric/isokinetic testing — all produced confidence intervals that crossed zero, meaning the data do not support a strength-enhancing effect. The authors were explicit that no evidence exists to back a strength claim.

Functional capacity, assessed at both short- and long-term intervals, similarly showed no statistically significant improvement. Confidence intervals were wide in both cases, reflecting substantial variability across the included studies.

The authors note that the devices used across studies differed considerably in wavelength (655–905 nm), power output, energy delivered per point, and application time, making it difficult to attribute the fatigue finding to any single protocol configuration. Most included studies were rated at low risk of bias using the RoB2 tool, and evidence quality was graded using GRADE.

Limits worth knowing

The meta-analysis included only 16 trials and 340 total participants, which is a modest evidence base for broad conclusions. All participants were described as healthy individuals, so findings do not extend to clinical or patient populations. The wide heterogeneity in device parameters — spanning wavelengths, power levels, and energy doses — introduces meaningful variability that the pooled analysis cannot fully account for. Funding sources for the included trials and for the review itself are not disclosed in the abstract, leaving potential conflicts of interest unassessed. The review did not examine long-term follow-up beyond what individual trials reported, and outcomes such as subjective wellbeing, sleep, or cardiovascular markers were outside its scope.

About this entry. The Heartwood Review summarizes published, peer-reviewed research in its own words and links to the original source. It is not medical advice; consult a physician before beginning or changing any thermal or recovery practice. Findings summarized here describe the study cited, not any product sold by Teak & Marble Atelier. Corrections.