Chen H. et al. - Photobiomodulation as an Adjunct to Muscle Strength Training in Older Adults: A Systematic Review and Meta-Analysis

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In this meta-analysis, photobiomodulation combined with periodized strength training did not significantly improve maximum strength in older adults compared with a light placebo. The authors report a negative result for the primary outcome, without ruling out a small effect.

What this study measured

Does adding photobiomodulation sessions to a muscle-strengthening program help older adults gain more maximum strength? Seven databases were searched through January 2026. Eligible trials used photobiomodulation delivered by low-level lasers or light-emitting diodes.

Eleven randomized controlled trials involving a total of 456 participants were included. Five of these studies, which combined photobiomodulation with periodized strength training and measured one-rep maximum load, could be pooled: 74 participants in the photobiomodulation group and 72 in the control group. The others were included in a narrative review. The abstract does not mention a PROSPERO registration.

Key Findings

The primary outcome measure—maximum strength, as measured by the maximum one-rep maximum—did not show a statistically significant improvement.

Maximum force: standardized mean difference of 0.26 (95% CI: −0.08 to 0.59), p = 0.14; not statistically significant compared with simulated photobiomodulation.
Very low heterogeneity among the aggregated trials: I² = 4%.
Scope: 11 trials and 456 participants in the review; 5 trials and 146 participants in the meta-analysis.
Subgroups: no significant trend in the one-sided tests, no effect in the two-sided tests, no differences between subgroups.
Sensitivity analyses show that the one-sided signal was driven by isolated trials.

Apart from muscle strengthening, some studies report possible benefits regarding fatigue or recovery in frail individuals, which the authors consider inconsistent.

How photobiomodulation works for this indication

The proposed mechanism remains hypothetical and has not been tested here. Red and near-infrared light is thought to be absorbed by cytochrome c oxidase, the terminal complex of the mitochondrial respiratory chain, which could increase ATP availability in the muscle. A modulation of oxidative stress and local inflammation following exercise is also suggested. These mechanisms would explain effects on recovery rather than on maximum strength, consistent with the negative result observed.

Limits You Should Know

The first limitation is the result itself: the effect on maximum strength is not significant, and the confidence interval includes zero. This negative result must be accepted as is.

Only 5 of 11 trials could be included in the meta-analysis, involving 146 participants—a sample size that remains too small to detect even a modest effect. Irradiation parameters, wavelengths, and protocols vary from one trial to another, and the abstract does not specify an optimal dose. Sensitivity analyses show a dependence on individual trials, which precludes any conclusions regarding unilateral movements. The favorable findings in frail individuals are based on a narrative synthesis, which has a lower level of evidence.

What This Means in Practice

For an older adult seeking to gain strength, the key factor remains progressive muscle strengthening itself. Based on these findings, photobiomodulation cannot be presented as a means of increasing maximum strength gains. The authors suggest that it may be beneficial for recovery in vulnerable individuals, a hypothesis that requires further large-scale trials.

Frequently Asked Questions

Does photobiomodulation increase muscle strength in older adults?

In this meta-analysis of 5 pooled randomized trials, no. The standardized mean difference is 0.26 (95% CI -0.08 to 0.59), with a p-value of 0.14, which is below the threshold for statistical significance. The authors note that a small effect cannot be ruled out.

How many studies were analyzed in this review?

Eleven randomized trials involving a total of 456 participants were included. Five of these trials, involving 146 participants, met the criteria for the quantitative meta-analysis on maximum strength. The other six were described in a narrative review.

Should photobiomodulation be excluded from a strength-training program?

This study does not show any benefit in terms of maximum strength, but that does not mean the approach is without value in other areas. The authors mention indications regarding fatigue and recovery in frail individuals, but these findings remain inconsistent. The decision rests with the healthcare professional treating the individual.

Reference

Chen H, Eungpinichpong W, Asawaphureekorn S, et al. Photobiomodulation as an Adjunct to Resistance Training in Older Adults: A Systematic Review and Meta-Analysis. Photobiomodulation, Photomedicine, and Laser Surgery, 2026. PMID 42473844. View the study on PubMed

This summary is provided for informational purposes only and does not constitute medical advice. Photobiomodulation is not a substitute for prescribed treatment. Consult a healthcare professional.