Photobiomodulation and Muscle Recovery: Timing Matters More Than Dose

What is photobiomodulation and how does it act on muscles?

Photobiomodulation (PBM), formerly known as low-level laser therapy (LLLT), is the application of non-coherent or coherent light in the red (630–700 nm) and near-infrared (750–1100 nm) ranges. The primary cellular target is cytochrome c oxidase, complex IV of the mitochondrial respiratory chain. Photon absorption by cytochrome c oxidase accelerates electron transfer, increases ATP synthesis and reduces reactive oxygen species concentration.

Applied to muscle recovery, the hypothesis is as follows: light exposure before exercise optimises mitochondrial function and strengthens cellular defences — thereby reducing the magnitude of oxidative stress and inflammation that will arise in response to mechanical muscle damage. This explains why timing — before rather than after exercise — turns out to be critical.

What does the meta-analysis of 24 RCTs show?

Luo et al. (Sports Health, 2022, DOI: 10.1177/19417381211039766, PMC: 9460079) analysed 24 RCTs and crossover studies involving athletes aged 15–40. All significant effects were observed in groups where PBM was applied before exercise.

• Lower-limb muscle strength (pre-exercise): at 24 h SMD = 1.97 (95% CI 1.01–2.93); at 48 h SMD = 2.02; at 96 h SMD = 2.68 (95% CI 1.57–3.79) — large effects.
• Muscle soreness (DOMS) immediately after exercise: SMD = −1.54 (95% CI −2.90 to −0.19) — significant reduction.
• Creatine kinase (at 48 h, PBM before exercise): SMD = −2.91 (95% CI −4.70 to −1.12) — significant reduction in muscle damage marker.
• Interleukin-6: SMD = −1.98 (95% CI −3.14 to −0.81) — significant reduction of pro-inflammatory cytokine.
• Blood lactate: SMD = −0.45 (95% CI −0.78 to −0.13) — significant reduction.

Post-exercise PBM application: neither strength at 24–96 h, nor CK, nor repetition count showed statistically significant effects. This asymmetry is one of the most practically important conclusions of the review.

Does PBM reduce soreness in delayed onset muscle soreness?

The meta-analysis by Tsou, Chang & Chang (Journal of Functional Morphology and Kinesiology, 2025, DOI: 10.3390/jfmk10030277, PMID: 40700213) included 14 controlled studies (of which 4 provided data for meta-analysis) and found:

• Pain (VAS) at 72 h: SMD = −0.55 (95% CI −0.95 to −0.15, p < 0.05) — moderate effect.
• Pain (VAS) at 96 h: SMD = −0.56 (95% CI −0.96 to −0.16, p < 0.05) — moderate effect.
• Muscle strength at 24 h: SMD = 0.97 (95% CI 0.15–1.80, p < 0.05) — large effect.
• Muscle strength at 48 h: SMD = 0.99 (95% CI 0.05–1.92, p < 0.05) — large effect.

10 of 14 studies reported positive effects of PBM therapy. Heterogeneity is high (I² = 67–81%), which limits the generalisability of conclusions.

Does PBM affect running performance?

No. A meta-analysis of 12 RCTs (Nascimento et al., International Journal of Exercise Science, 2024, DOI: 10.70252/BUWB9550, PMC: 11042871) showed: pooled SMD = 0.13 (95% CI −0.03 to 0.29; p = 0.11) — a statistically non-significant result. The authors noted that most studies used doses below 1,000 J and recommended future studies test higher protocols. Jump height also did not improve significantly in available data.

What are the parameters of effective protocols?

The review by Lawrence & Sorra (JFMK, 2024, DOI: 10.3390/jfmk9040181, PMC: 11503318) summarised parameters from 64 studies of sport applications:

• Wavelengths: 632.8–980 nm; most commonly 808–850 nm and 905 nm; red range 655–680 nm combined with near-IR showed the best results.
• Power: 10–534 mW; class IIIb devices (5–500 mW) and class IV (>500 mW).
• Dose per point: 0.095–50 J; typical effective protocols 10–60 J per session on local muscle groups.
• Placement: directly on target muscle bellies (2 points per thigh muscle showed the best strength results).
• Frequency: 2–4 times per week in the majority of positive protocols.