Leal-Junior E.C. et al. - Photobiomodulation, Exercise Performance, and Muscle Recovery: A Systematic Review with Meta-Analysis

This systematic review with meta-analysis evaluated low-level laser therapy or light-emitting diode (LED) therapy administered around the time of exercise. The authors concluded that there was an improvement in muscle performance and accelerated recovery, primarily when the light was administered before exercise.

What this study measured

The research question was whether phototherapy can modulate activity-induced muscle fatigue or subsequently protect against muscle damage. The authors searched the PubMed/Medline database and selected randomized controlled trials published between 2000 and 2012. Methodological quality was assessed using the PEDro scale, which consists of ten items.

Three main criteria were defined: the number of repetitions and time to exhaustion for muscle performance, and creatine kinase activity to estimate the risk of exercise-induced muscle injury. The review identified 16 randomized trials; three were excluded due to insufficient quality.

Key Findings

Thirteen studies of acceptable quality—defined as a score of at least 6 out of 10 on the PEDro scale—were analyzed. Twelve of them applied light before exercise.

• Time to exhaustion: a 4.12-second increase compared with placebo (95% CI 1.21 to 7.02; p < 0.005).
• Number of repetitions: a 5.47-fold increase compared with placebo (95% CI 2.35 to 8.59; p < 0.0006).
• Ten out of thirteen trials reported a significant improvement in the primary performance-related outcomes.
• Biochemical markers: The heterogeneity of the protocols precluded any meta-analysis, but a quantitative analysis showed favorable results in 13 out of 16 comparisons.
• Parameters associated with the clearest results: red or infrared wavelengths, application before exercise, power levels between 50 and 200 mW, and doses of 5 and 6 J per point.

How photobiomodulation works for this indication

The mechanism has not been measured here and remains hypothetical. Red and near-infrared light is thought to be absorbed by cytochrome c oxidase, the terminal complex of the mitochondrial respiratory chain, which would increase ATP availability in the muscle fiber. A modulation of oxidative stress and local inflammation is also suggested as an explanation for the reduced release of creatine kinase. The fact that the most pronounced results come from pre-exercise application points to a preconditioning effect.

Limits You Should Know

The measured effects are statistically significant but modest in magnitude: a gain of 4.12 seconds in time to exhaustion and 5.47 additional repetitions. The confidence intervals are wide, reflecting a genuine degree of imprecision, and the practical implications of these gains in real-world athletic performance are not established by this review.

The literature search was limited to a single database, PubMed/Medline, which introduces a risk of selection bias. The abstract does not mention any protocol registration, assessment of publication bias, or total number of participants. Finally, this meta-analysis covers trials published through 2012: significantly more recent studies exist and should be consulted for an up-to-date overview.

What This Means in Practice

These findings suggest that photobiomodulation may serve as a complementary approach to exercise, rather than a substitute for physical training. The most useful factor is the timing of application: studies in which light was applied before exercise yielded the most consistent results. The parameters associated with the best results are derived from the included studies and do not constitute a recommendation.

Frequently Asked Questions

Should you use the light before or after exercising?

The authors conclude that the effects are primarily observed when phototherapy is administered before exercise. Twelve of the thirteen included trials followed this approach, and it is this protocol that yielded the most consistent results regarding performance.

By how much is performance improving?

The time to exhaustion increased by an average of 4.12 seconds (95% CI 1.21 to 7.02), and the number of repetitions increased by 5.47 (95% CI 2.35 to 8.59) compared with the placebo. These gains are statistically significant but modest, and their impact in competition is not evaluated here.

Does photobiomodulation reduce muscle damage after exercise?

The review reports favorable results in 13 out of 16 comparisons for biochemical markers, including creatine kinase. However, the heterogeneity of the protocols made it impossible to calculate a pooled effect, which makes this conclusion less robust than the one regarding performance.

Reference

Leal-Junior EC, Vanin AA, Miranda EF, et al. Effect of phototherapy (low-level laser therapy and light-emitting diode therapy) on exercise performance and markers of exercise recovery: a systematic review with meta-analysis. Lasers in Medical Science, 2013. PMID 24249354. 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.