Photobiomodulation (PBM), also called low-level light therapy or low-level laser therapy, uses red or near-infrared light in an attempt to influence biological tissue. It is marketed for recovery, soreness, performance, and muscle growth.
The evidence is more specific than the marketing. Some reviews report small acute effects on exercise tolerance or repetitions, while longer-term strength and hypertrophy evidence remains limited, mixed, and highly dependent on the population and device protocol.
What PBM is supposed to do
PBM research investigates how light delivered to tissue may interact with cellular and vascular processes. Mechanistic explanations often mention mitochondrial signalling, oxidative stress, inflammation, and blood flow. Those mechanisms can be plausible without proving a meaningful change in a lifter's training adaptation.
The intervention is not one standard treatment. Studies differ in wavelength, irradiance, energy density, contact method, treatment area, timing, and whether the source is a laser or an LED. A consumer panel cannot be assumed to reproduce a laboratory protocol just because both emit red light.
What the exercise evidence shows
A 2025 systematic review and meta-analysis included 12 studies with 346 young adults and found an overall improvement in the maximum number of repetitions compared with placebo. The pooled mean difference was about four repetitions, but the studies were acute, heterogeneous, and not evidence that PBM builds more muscle over months.
Other reviews have reported possible benefits for fatigue, recovery, or performance, but the certainty and consistency vary. A 2026 systematic review and meta-analysis in older adults found no statistically significant improvement in maximal strength when PBM was added to resistance training. A small effect cannot be ruled out, but “no clear additional benefit” is a very different claim from “proven recovery technology.”
What it does not establish
Current exercise evidence does not establish that PBM:
- directly causes hypertrophy without progressive resistance training;
- lets a lifter train through pain or an injury;
- guarantees less soreness or faster recovery;
- works better when a device uses a particular consumer label; or
- has one universally effective wavelength, dose, timing, or weekly schedule.
An acute repetition result can be interesting while still being too small, short, or specific to guide a long-term muscle-building claim.
How to evaluate a device or claim
Before spending money, ask:
- Is the claim about repetitions, soreness, strength, muscle size, or a medical condition?
- Does the cited study use the same outcome, population, body site, and device type?
- Are the device's wavelength and delivered dose measured, rather than inferred from marketing language?
- Is there a sham-controlled comparison and a meaningful follow-up period?
- Does the purchase still make sense if the effect is small or absent?
If you try PBM, keep your training and recovery log unchanged enough to evaluate it. Do not use it to justify more load, more frequency, or training through unexplained pain.
Safety and medical context
Follow the device instructions, use eye protection when required, and avoid treating a medical condition based on a fitness advertisement. A clinician or qualified therapist should guide use for an injury, chronic pain, photosensitivity, medication interaction, or other medical concern.
The bottom line
PBM is a plausible research intervention with some evidence for small, acute exercise effects. It is not yet a reliable hypertrophy tool, and consumer-device claims often go beyond the trials. Treat it as optional and unproven; the fundamentals remain progressive training, nutrition, sleep, and appropriate recovery.
Related reading
- Red Light Therapy for Muscle Growth: What Science Actually Says
- Training Around Injuries: How to Keep Gains Without Ignoring Risk
Limits of the evidence
PBM studies use different devices, doses, muscles, timings, outcomes, and participant groups. Some findings are acute and some are in older or clinical populations. They should not be combined into a universal protocol or long-term hypertrophy promise.
Sources
- Acute effects of photobiomodulation therapy on the maximum number of repetitions in resistance exercise. 2025 systematic review and meta-analysis; acute repetition outcome and heterogeneous protocols.
- Photobiomodulation as an adjunct to resistance exercises among older adults. Scoping review showing varied studies and dosimetry in older adults.
- Photobiomodulation as an adjunct to resistance training in older adults. 2026 systematic review and meta-analysis; no significant maximal-strength benefit versus sham in the prespecified meta-analysis.
- Photobiomodulation therapy for muscular performance and fatigue. Earlier systematic review and meta-analysis; useful historical context, not a universal device prescription.
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