Red light therapy muscle recovery routines are popular, and “muscle recovery Reddit” threads are full of personal experiences. This page sets out what researchers have actually measured on sore muscles after exercise, where they found little or nothing, and why device settings matter. It covers workout soreness only.
Before you read on: research findings come from specific devices, settings and groups of people. They may not apply to any particular device or person.
This is general information, not medical advice. If you have an injury or ongoing pain, please see a physio or doctor.
What does the research say about muscle soreness after exercise (DOMS)?
Delayed onset muscle soreness (DOMS) is the stiffness and tenderness that can build up a day or two after unfamiliar or hard exercise. It’s usually what people mean when they search for red light therapy sore muscles. Studies have looked at this by having volunteers do a set exercise designed to cause soreness, then applying real or sham (placebo) light.
A 2025 systematic review and meta-analysis. Tsou, Chang and Chang found 14 controlled studies published between 1996 and 2022. Light was applied after the soreness-inducing exercise, at wavelengths of 660 to 950 nm, to between one and six points on the working muscle. Ten studies reported at least one positive result and four reported no significant differences.[1]
Only four studies had usable data to pool. Compared with placebo, the pooled results showed lower soreness ratings at 72 and 96 hours after exercise. They also showed better muscle strength at 24 and 48 hours.[1]
Limits: most studies were small, with about 6 to 20 people per group. Nine of the 14 tested the biceps (upper arm) rather than larger leg muscles. Study quality scores ranged from 4 to 9 out of 10. The meta-analysis rested on only four studies. Light settings and outcome measures varied widely, which the authors said makes comparisons hard. The authors called for larger, higher-quality studies with well-defined settings. The review received no funding and the authors declared no conflicts.[1]
Where did studies find little or no benefit, and why might results vary?
Inside the 2025 review. Several included studies found no significant differences between real and sham light. One found no differences in any measure, and another found none for soreness ratings. Two found no difference in jump or agility tests. The authors suggested light may make less difference to short, explosive movements.[1]
A 2020 controlled trial. Tsuk and colleagues ran two crossover, double-blinded, placebo-controlled experiments with 60 physical education students aged 20 to 35 (30 per experiment). They used a small home-use laser (808 nm), with three units held against the thigh muscles at once, for a total of about 150 joules.
The trial measured knee-extension strength and work on a dynamometer, plus blood lactate and heart rate. It didn’t measure soreness. Researchers found no differences between real and sham laser in strength, or in recovery straight after a fatiguing set of knee extensions.[2]
Limits: outcomes were measured within minutes, so any delayed effect wouldn’t have been captured. The authors suggested the dose may have been too low, noting other trials used different doses with different results. It used a laser, not LEDs. We didn’t find a funding statement in the article.[2]
Why might results vary? The reviewers and trial authors pointed to the same factors:[1][2]
- different wavelengths, power and time per point
- different muscles
- different exercise protocols
- different outcomes, such as soreness ratings, strength or blood markers
- different measurement times
The underlying mechanism is also still debated (see how red light works).
Is it better before or after training?
Should you use red light therapy before or after a workout? Our sources don’t settle it. The 2025 review included only studies where light was applied after the soreness-inducing exercise. It excluded studies of light given beforehand, and the authors said pre-exercise use still needs study.[1]
The 2020 trial applied light around exercise and found no differences. Its own text describes the timing inconsistently, so we haven’t drawn a timing conclusion from it.[2] The evidence on timing is mixed and limited.
What dose and distance do deeper muscles need, and why do device specs matter more here than for skin?
There’s no agreed dose for muscles. In the 2025 review, device output ranged from about 10 to 534 milliwatts, and time per point from 10 seconds to 12 minutes.[1] In the muscle studies we reviewed, light was usually applied at marked points on the muscle, and in the 2020 trial the device was held against the skin.[1][2] None of our sources set a distance for panels used on muscles.
Why dose matters. De Freitas and Hamblin described a biphasic dose response: too little light may do nothing measurable, and too much may cancel the effect.[3] A 2026 consumer product guide made the same point. It noted that the published irradiance (mW/cm²) and fluence (J/cm²) ranges for skin, about 20–60 mW/cm² and 4–18 J/cm², vary so widely that dosing isn’t standardised.[4] Those are skin figures, not muscle figures.
Red light therapy for muscle recovery wavelength. The same guide described red light (about 630–660 nm) as absorbed mostly in the upper layers of skin, and near-infrared (about 830–850 nm) as reaching deeper tissue.[4] Most of the muscle studies used near-infrared or combined red and near-infrared light.[1]
Why specs matter more here. For skin, the target is close to the surface. For muscle, light has to pass through skin and other tissue first. Light also spreads out as you move a device away, so a panel delivers less light per square centimetre at 30 cm than up close. That’s why it helps to see irradiance measured at a stated distance, not just the number of LEDs. See how to choose a device and mask vs panel.
How does red light compare with other recovery habits like heat, rest and sleep?
None of our sources compared red light with heat, rest or sleep, so we can’t say how they stack up. The 2025 review noted that DOMS usually eases by itself within a few days. It also listed other approaches researchers have studied, such as cold, massage and stretching.[1]
Some practical points, which aren’t claims:
- If you use red light, think of it as optional, not a replacement for basics like rest, sleep, food and a sensible training load.
- Check your device’s eye-safety guidance and session times. See is red light therapy safe?
- Be cautious of combo gadgets or posts promising faster results. See red light therapy myths vs facts.
What about athletes? The red light therapy recovery trials we reviewed mostly involved students and other volunteers doing set lab exercises, not elite athletes in training seasons.[1][2]
When should I see a physio or doctor instead?
Normal workout soreness usually fades over a few days.[1] See a physio or doctor if:
- soreness lasts longer than expected, keeps getting worse, or comes with marked swelling, weakness or dark urine
- you think you’ve been injured, for example after a sudden sharp pain, a pop, a fall or a knock
- you have joint pain or back pain; this page doesn’t cover those, so please get personal advice
A physio or doctor can assess what’s going on and suggest a plan. If a device is promoted for a therapeutic purpose, you can check its ARTG entry (see our guide to TGA and ARTG).
FAQ
Does red light therapy help sore muscles? Some trials found lower soreness ratings or better strength after exercise compared with placebo, and others found no difference. The pooled evidence came from only four small studies.[1][2]
What wavelength did muscle studies use? Between 660 and 950 nm, often near-infrared or red plus near-infrared.[1]
Should I use it before or after a workout? The evidence is mixed and limited. The main review only included use after exercise.[1]
How close should a panel be? Our sources don’t give a distance for muscles. Look for irradiance published at a stated distance.[4]
Is it a replacement for rest or physio? No. None of our sources compared it with those, and injuries or ongoing pain need personal advice.
If you have ongoing pain, an injury, or joint or back pain, please see a physio or doctor.
Related reading on our blog
- Red light therapy before or after a workout?
- How often should you use red light therapy?
- How to build a simple evening red light therapy routine
Sources
- Tsou YA, Chang NJ, Chang WD. Effects of photomodulation therapy for delayed onset muscle soreness: a systematic review and meta-analysis. Journal of Functional Morphology and Kinesiology. 2025;10(3):277. https://doi.org/10.3390/jfmk10030277
- Tsuk S, Har Lev Y, Fox O, Carasso R, Dunsky A. Does photobiomodulation therapy enhance maximal muscle strength and muscle recovery? Journal of Human Kinetics. 2020;73:135–144. https://doi.org/10.2478/hukin-2019-0138 (open access: https://pmc.ncbi.nlm.nih.gov/articles/PMC7386143/)
- de Freitas LF, Hamblin MR. Proposed mechanisms of photobiomodulation or low-level light therapy. IEEE Journal of Selected Topics in Quantum Electronics. 2016;22(3). https://doi.org/10.1109/JSTQE.2016.2561201
- Spongberg CV, Stack ER, Aprigliano C, Grinis D, Sawicki S, Elway M. What to look for in red light therapy: a product guide backed by science. Cureus. 2026;18(3):e105378. https://doi.org/10.7759/cureus.105378 (open access: https://pmc.ncbi.nlm.nih.gov/articles/PMC13085462/)
