Can red light therapy increase muscle recovery and muscle mass?

Helmut uses his panels around training, so this question comes up a lot, and it deserves a proper answer rather than a slogan. The short version: there is a real body of trials, most of them small, the best results come from light applied before exercise, and two well-run studies found nothing at all. Here is what they say.

What the 2016 review actually says

The paper everyone quotes is a 2016 review by Ferraresi, Huang and Hamblin in the Journal of Biophotonics. It is a review, not a single study: the authors searched the literature up to 2016, kept 46 trials covering 1,045 participants, and sorted the light settings into those that improved muscle performance and recovery and those that did not. Their conclusion is the line on our research page: light around training "can increase muscle mass gained after training, and decrease inflammation and oxidative stress in muscle biopsies", to the point that they "raise the question of whether PBM should be permitted in athletic competition by international regulatory authorities". Those are the authors' words, and they are striking. They are also a summary of 46 mostly small trials, which is why the rest of this post is about the trials.

Before training or after?

Before, on the balance of the evidence. A 2023 review of 15 randomised trials concluded light therapy "has a positive effect on sports performance", most consistently when applied before exercise, in contact with the skin, at 655-950nm, with reduced muscle damage in five of seven strength studies. A 2021 narrative review of 25 human studies published since 2014 found protective and performance effects, again with pre-exercise use the common thread. The 2016 review calls this pre-conditioning: light delivered to the muscle before the work.

The studies that stand out

The one people remember is the identical twins. Two twin soccer players did the same 12-week strength programme; one had 850nm LED on the trained muscles after every session and the other a placebo. The LED twin gained 20% thigh muscle volume against 5%, improved leg-press strength 53% against 28%, had less soreness and smaller creatine kinase rises. It is a study of two people, so it is a demonstration rather than proof, but it is a clean one.

In 28 healthy men given 630nm red or 940nm near-infrared LED before a damaging plyometric workout, both wavelengths improved jump recovery over 72 hours, only the 940nm arm cut the creatine kinase rise, and pre-treating did not blunt the body's own "repeated bout" adaptation. In 40 people with exercise-induced soreness, 830nm LED raised pressure-pain thresholds at 48, 72 and 96 hours and improved range of motion, while swelling and strength were no different from placebo. And in 28 soccer players an 810nm five-diode cluster before eccentric exercise increased strength and lowered soreness and damage markers over 96 hours, with the lowest power setting working best - that one used lasers, and the authors of a separate review note that LED light can be as effective as laser, with similar biological effects.

The null results

Two trials deserve equal billing because they found nothing. Twelve trained men used a whole-body 660 and 850nm LED bed for 15 minutes before and after a heavy resistance workout, and creatine kinase over 72 hours and salivary IL-6 were no different from sham. In 36 healthy men, a 660-850nm LED cluster after sprint-interval sessions changed none of the inflammatory markers, soreness or jump performance, and matched cold-water immersion and active recovery. The bed study applied the light before and after the session, the cluster study afterwards. The fair summary is that the effect depends on timing, dose and where the light goes, and that whole-body beds at low settings have not shown what targeted, pre-exercise light has.

How we use it

Helmut uses his panels before the gym and again afterwards: the first session is the pre-conditioning the reviews describe, the second is for how he feels the next day. For session times, the Dosage Estimator has a "High-dose large muscle" preset based on the doses used in the research. For a specific muscle or joint, HeroBelt™ puts the light in contact with the skin, which is how most of the positive trials applied it; for legs and back together, a panel. The muscle recovery collection groups the devices, and the device finder will narrow it down.

What about the athletes?

Red light has reached professional sport. NBA star LeBron James has described using it for muscle and joint pain, and the San Francisco 49ers built a dedicated light therapy recovery room; the sources for each are on our Celebrities & Athletes page, which only lists what people have said publicly. An earlier version of this post named other athletes without a source; they are gone until we have one. The muscle research page has every study above and more, wavelength by wavelength.