Red Light Before vs After Workout for Muscle Growth

About the author

Evelyn Reed, M.S.

Health Science EducatorCertified Wellness Coach

Evelyn Reed, M.S., is a Health Science Educator and Certified Wellness Coach specializing in evidence-based, at-home wellness solutions. With a Master's degree in Health Science, she focuses on translating complex scientific research on cellular health and light therapy into practical, accessible protocols. Evelyn is dedicated to empowering individuals to manage pain, improve sleep, and enhance skin vitality. Her science-first, empathetic approach makes her a trusted advocate for achieving long-term health goals.

Red Light Before vs. After Workout: Which Boosts Muscle Growth More?

When people add an at‑home red light panel to their gym corner, one of the first questions I hear is very simple: if the goal is muscle growth, should I stand in front of the red light before I lift, or after I rack the last set?

As a red light therapy wellness specialist, I see both curiosity and understandable skepticism. You work hard for every pound of strength and every inch of muscle. You do not want to chase a gimmick, but you also do not want to miss a safe tool that could give you an extra edge.

In this article, I will walk you through what credible research says about red light therapy, how it interacts with resistance training, and what we actually know about using it before vs after workouts for hypertrophy. I will lean on evidence from independent reviewers such as Examine.com, medical centers like MD Anderson Cancer Center and University Hospitals, and peer‑reviewed trials summarized in sports medicine and rehabilitation literature. At the same time, I will keep this practical and grounded in real‑world experience with home devices and busy training schedules.

How Red Light Therapy Affects Muscle Tissue

Red light therapy, often called photobiomodulation or low‑level laser therapy, uses low‑energy red and near‑infrared light, usually in the range of roughly 630–850 nanometers, to influence how cells work. Unlike tanning beds, it does not emit ultraviolet light, does not tan or burn the skin when used correctly, and is considered non‑invasive and non‑thermal according to clinical descriptions from MD Anderson Cancer Center and WebMD.

Multiple sources, including Stanford Medicine and reviews hosted on the National Institutes of Health’s open‑access platforms, describe a common core mechanism. Photons of red and near‑infrared light are absorbed by chromophores in mitochondria, particularly an enzyme called cytochrome c oxidase. When this happens, several things seem to occur at once: mitochondrial activity increases, adenosine triphosphate (ATP) production rises, nitric oxide is released and can promote vasodilation, and downstream signaling alters inflammatory and antioxidant pathways.

In plain language, that means well‑dosed red light can help your muscle cells make more energy, increase local blood flow, and shift the chemical environment toward less inflammation and better repair. Sports recovery articles from clinics and gyms, such as City Fitness and other athletic centers, emphasize these effects in practical terms. They describe reduced soreness, faster bounce‑back between sessions, and support for older joints that do not recover as quickly as they used to.

Different wavelengths reach different depths. Red light around 630–660 nanometers tends to act on more superficial tissues, which is why dermatology and hair clinics use it for collagen stimulation and hair follicle support, as described by Stanford dermatology experts and WebMD. Near‑infrared light around 810–850 nanometers penetrates deeper into muscle, fascia, and even near bone, making it the workhorse for performance and musculoskeletal recovery in many athletic protocols summarized by sports medicine providers.

Overall, major medical centers portray red light therapy as relatively low risk when used properly, while also stressing that evidence for many newer claims, especially around sports performance and systemic benefits, is still developing. University Hospitals and Stanford both highlight that athletic and performance benefits remain less solidly proven than skin and hair applications.

What The Science Says About Muscle Growth And Performance

Muscle size and strength over weeks of training

The most relevant studies for hypertrophy are those that combine red light therapy with a resistance‑training program for several weeks and then measure muscle size and strength.

An open‑access randomized, placebo‑controlled trial using light‑emitting diode therapy during a lower‑body strength program found that participants who received real near‑infrared and red light over the trained muscle before each workout gained more muscle cross‑sectional area and strength than those who trained with a sham device. According to the researchers’ summary, the light‑treated group also showed less rise in blood markers of muscle damage, reported less delayed‑onset muscle soreness (DOMS), and showed gene expression changes that favored muscle growth, mitochondrial energy metabolism, and antioxidant defenses. Importantly, no meaningful adverse events were reported.

The independent research group Examine.com reviewed the long‑term training literature and reached a cautious but similar conclusion in young adults. They note that in one multi‑week study of young men, red light therapy applied before strength training led to greater increases in muscle size and strength than training alone. At the same time, Examine.com points out that an analogous study in older men found no additional benefit of pre‑exercise red light on strength or muscle mass, and that a study in older women who received red light after strength training did not show extra strength gains and did not report muscle size at all.

Clinical sports‑medicine summaries, such as those compiled by physical therapy centers and sports performance clinics, add more nuance. They highlight trials where photobiomodulation used after strength training promoted muscle hypertrophy, improved muscle thickness and peak torque, and reduced biomarkers of muscle damage and inflammation. One twin study described in these summaries reported that post‑training red light enhanced muscle growth and modulated genes involved in hypertrophy compared with the non‑treated twin.

Stepping outside the gym, a network meta‑analysis in critically ill adults with ICU‑acquired weakness found that “light therapy” in that context significantly improved muscle strength. These patients are very different from recreational lifters, but the finding reinforces that photobiomodulation can, under some circumstances, support muscle function.

Taken together, the hypertrophy evidence looks like this. In healthy younger men, there are small randomized trials where red light therapy before training enhanced muscle size and strength compared with training alone. In some clinical and sports settings, red light delivered after training has also been associated with more muscle growth and better strength metrics. In older populations, especially when red light was applied after training, at least one study found no additional strength benefit. Across all of these, sample sizes are small, protocols differ widely, and the effect appears to be additive rather than transformative.

Performance during a single workout

If red light therapy can help you perform better in a given workout, that could indirectly support muscle growth by letting you do more high‑quality volume.

Examine.com’s evidence review notes that red or near‑infrared light applied immediately before resistance exercise has, in some studies, slightly increased repetitions to failure in eccentric movements such as biceps curls and knee extensions. However, most of these positive findings come from a narrow group of young male volleyball players studied by a single research team. Other trials using similar pre‑workout light protocols have not found performance benefits, suggesting that any ergogenic effect is small and not reliable.

A 2015 systematic review and meta‑analysis of randomized, placebo‑controlled trials, summarized by performance‑focused wellness writers, concluded that photobiomodulation before exercise improved metrics such as maximal repetitions, speed, endurance, and time to exhaustion versus placebo. Single trials in field sports and cycling reported longer time to exhaustion, better running economy, improved sprint performance, or more time on the pitch when athletes received pre‑event red light therapy. At the same time, other triple‑blind and crossover designs, highlighted in a comprehensive review of 46 clinical studies on photobiomodulation in human muscle, observed little or no improvement in repetitions, torque, lactate, or DOMS.

A consistent theme in that large review is that results depend heavily on details such as wavelength, energy density, number and placement of treatment sites, and timing relative to exercise. Animal work suggests a biphasic dose response, where too little energy does nothing and too much can blunt benefits, but this “sweet spot” is not well mapped for humans.

The bottom line for in‑workout performance is that some protocols, especially pre‑workout exposures in young, healthy men, show meaningful improvements in fatigue resistance and work output, while others show no effect. Independent reviewers repeatedly emphasize that even when benefits appear, they are small compared with what you can gain from sound programming, nutrition, and sleep.

Recovery, soreness, and biomarkers of muscle damage

Many lifters are drawn to red light mainly for recovery. Faster recovery theoretically supports hypertrophy by allowing higher training frequency and volume.

Recovery‑oriented sources such as Greentoest Tucson, City Fitness, and other athletic recovery centers describe consistent real‑world experience: red light therapy sessions after strength training often feel as though they reduce soreness and stiffness and shorten the time needed to feel ready for the next session. They highlight a 2016 review indicating that red light after training can reduce muscle soreness, lower markers of muscle damage, and speed the recovery of strength and power.

The broader scientific picture is more mixed but still interesting. The large photobiomodulation review mentioned earlier notes that after muscle‑damaging elbow flexor protocols, post‑exercise light therapy has been associated in randomized trials with reduced DOMS, slower decline in isometric force, and less restriction in joint range of motion for up to about four days. However, improvements in soreness have not always translated into measurable performance or load‑lifting advantages.

A 2019 comparative review summarized by a sports medicine supplier evaluated three clinical trials and two animal studies that directly compared cryotherapy with red light therapy for post‑exercise recovery. Across all five studies, red light therapy outperformed cryotherapy for reducing DOMS and muscle inflammation. Biomarkers like creatine kinase, a marker of muscle damage, were significantly reduced in the red light groups but not in the cryotherapy groups. Interestingly, all of these red light protocols used relatively modest intensities, suggesting that more is not automatically better.

On the other side of the ledger, Examine.com highlights multiple studies where red light therapy did not reliably reduce delayed‑onset muscle soreness in the days following a workout. The comprehensive human muscle review also reports several high‑quality trials with no meaningful changes in soreness, lactate, or performance measures.

In short, there is credible evidence that red light therapy, often used after exercise, can reduce soreness and biochemical markers of muscle damage in some settings. There is also a nontrivial set of studies where it does very little. That is why independent reviewers and academic authors alike call the overall evidence “mixed, protocol‑specific, and based on a small number of trials.”

Pre‑Workout vs Post‑Workout: How Do They Really Compare?

Because studies rarely compare pre‑workout and post‑workout red light head‑to‑head, we need to look at patterns across the literature rather than a single decisive trial. The table below summarizes what the current evidence and clinical experience suggest.

Aspect	Pre‑workout red light	Post‑workout red light
Primary intent	“Pre‑conditioning” muscles to perform better and adapt more	Supporting recovery, soreness reduction, and tissue repair
Evidence for hypertrophy	Randomized training trials in young men and a multi‑week LED therapy study found extra gains in muscle size and strength when light was applied before each session compared with training alone, though sample sizes were small and older men did not benefit	Some clinical trials, including a twin study, show post‑training photobiomodulation can promote muscle hypertrophy and favorable gene expression; other work in older women found no additional strength benefit from post‑exercise light
Acute performance	Several small studies and a 2015 meta‑analysis show more repetitions, better fatigue resistance, and improved endurance when light is applied immediately before exercise; many other trials show no benefit	Rarely used solely for acute performance; most post‑exercise protocols target recovery rather than extra reps in the moment
Recovery and soreness	Some protocols show lower creatine kinase and less fatigue when light is used both before and after training; evidence is less focused on pre‑only recovery	A 2016 review and a 2019 comparative review report that post‑exercise red light reduces DOMS and muscle damage markers and outperforms cryotherapy, although other trials show no effect; commonly used for “I want to hurt less tomorrow” goals
Practical considerations	Requires planning into the warm‑up window; you need to be near your device shortly before training	Easy to pair with cooldown or evening routine; may feel relaxing and ritualistic after a hard session

Putting this together for a lifter whose main goal is hypertrophy, several points stand out.

First, when we look specifically at trials that actually measured muscle size and strength over time, the clearest positive data in healthy young men come from protocols where light was applied before each strength workout. The multi‑week LED therapy study and the long‑term trial highlighted by Examine.com both used pre‑exercise exposures and reported extra hypertrophy and strength compared with training without light.

Second, there is also evidence that post‑workout red light can promote muscle growth. The twin study summarized by sports medicine clinicians involved post‑training photobiomodulation and found increased muscle thickness and favorable gene expression compared with the non‑treated twin. Another clinical trial in which light was applied after strength sessions showed larger gains in lifting capacity and peak torque compared with training alone.

Third, not every population responds the same way. The older men in one pre‑exercise trial did not gain additional strength or mass from red light, and older women receiving post‑exercise light did not see extra strength benefits. That suggests age, sex, baseline training status, and possibly hormonal and mitochondrial differences influence outcomes.

Fourth, for pure recovery and soreness relief, a number of positive studies use post‑exercise protocols, and the direct comparisons with cryotherapy favor red light. That makes post‑workout or same‑day recovery sessions a reasonable choice if your priority is feeling ready for the next training day rather than squeezing out a marginal gain in today’s performance.

Given all of this, my evidence‑based, real‑world answer is that pre‑workout red light seems to have the strongest support when the specific outcome is “more muscle and strength from the same training plan,” especially in younger adults. Post‑workout red light has better, though still mixed, support for reducing soreness and biochemical markers of muscle damage, and there is at least some evidence that it can support hypertrophy as well. There is no high‑quality evidence that doing both pre and post around every session is dramatically better than an optimized single timing, and one trial summarized by sports clinicians even noted no extra benefit from adding post‑exercise light to an already effective pre‑exercise protocol.

Designing An At‑Home Red Light Routine Around Your Training

Keep the foundations first

Every independent reviewer, from Examine.com to University Hospitals, makes the same point: red light therapy should never replace the fundamentals. Progressive resistance training, adequate dietary protein and overall calories, smart programming with appropriate rest, quality sleep, and good stress management will determine almost all of your long‑term hypertrophy.

Red light therapy is best thought of as a possible amplifier. If your basics are in place, it might help you recover a bit faster or translate the same workouts into slightly better gains. If your basics are shaky, no amount of light will compensate.

Choosing a device for muscle goals

Medical centers such as MD Anderson, WebMD, and University Hospitals describe red light delivery in two broad ways: higher‑powered clinical systems used in supervised settings and lower‑intensity consumer devices used at home. Home options include wall‑mounted or free‑standing panels, flexible pads and blankets, masks, and small handheld wands.

For muscle and performance goals, panels or larger pads are generally more practical than tiny spot wands, because you need to cover big muscle groups like quadriceps, hamstrings, glutes, and back. Many sports‑oriented articles recommend devices that combine visible red wavelengths with deeper‑penetrating near‑infrared, echoing the approach used in clinical and research settings.

Wellness and sports recovery guidelines from sources like Poll to Pastern and Greentoest Tucson commonly describe protocols using red light around 630–660 nanometers and near‑infrared around 810–850 nanometers. They emphasize applying the light to clean, uncovered skin and placing LEDs close enough to meet device recommendations without causing discomfort.

Session length, frequency, and timing

Different studies and clinics use different “doses,” but several patterns repeat. City Fitness, which offers in‑club red light therapy, recommends about 10–20 minutes per session for general recovery and sleep support. Greentoest Tucson describes typical strength‑training recovery sessions of about 10–20 minutes in front of a panel. Poll to Pastern’s exercise‑recovery guide suggests using red light for roughly 20–30 minutes per area, up to three times daily for active healing or two to three times per week for maintenance.

Research trials often quantify dose in energy per square centimeter rather than minutes, and there is evidence of a biphasic response where both too little and too much energy are ineffective. Because of that, it is wise to start with moderate, manufacturer‑recommended session lengths rather than assuming that “longer is better.”

For hypertrophy‑focused lifters, a practical approach based on the current evidence looks like this. On strength days, treat pre‑workout exposure as your anchor. Aim to use your device in the window roughly 15–30 minutes before you begin your warm‑up, with about 10–20 minutes of reasonably close exposure for the main muscle groups you are about to train. That mirrors the timing used in many of the positive pre‑conditioning and training studies and fits recommendations from sports clinics that suggest using light shortly before exercise.

If you want to experiment with post‑workout recovery, especially after very heavy or high‑volume days that leave you sore for more than about two days, you can add a separate session later that day or in the evening. Recovery‑oriented sources generally describe similar session lengths for post‑exercise use, around 10–20 or 20–30 minutes depending on the body area. Pay attention to how your body feels and how your training log looks rather than simply layering on more and more exposure.

Integrating into a weekly training schedule

Imagine a four‑day upper–lower routine. On Monday and Thursday, you train lower body; on Tuesday and Friday, you train upper body. If you have a panel at home, you might step in front of it before each of these sessions, focusing on the muscles you plan to use.

On lower‑body days, that might mean ten to twenty minutes facing the panel so your quads, hips, and core receive light, then turning so your hamstrings and glutes get similar exposure. On upper‑body days, you might adjust your stance or chair position so shoulders, chest, and back are in the treatment zone.

After especially demanding workouts, such as heavy squats or deadlifts that you know usually leave you sore for days, you could add a second red light session later in the day targeting those same muscles. If you notice that soreness is shorter or less intense, and that you feel ready to push hard again sooner without accumulating fatigue, that is a good sign that the protocol is helping you.

There is no universally validated schedule, so treat your own body’s response as an experiment. If, after several weeks of consistent use, you cannot see any difference in how quickly you recover or progress, it is reasonable to scale back or redeploy the time and money toward other recovery tools.

Safety and medical considerations

Major medical centers consistently describe red light therapy as generally safe and low‑risk when used correctly. MD Anderson Cancer Center and University Hospitals note that side effects are typically mild when they do occur, and that serious complications are rare at the low intensities used for skin and muscle. The main precautions focus on eye and skin safety and on people with specific medical vulnerabilities.

Because light in the red and near‑infrared spectrum can still harm the eyes at high intensities, clinics require goggles or shields during treatments. Home users should avoid staring directly into bright panels and follow any eye‑protection instructions provided. WebMD and other sources also mention that high‑intensity applications can cause skin redness or blistering if misused.

Certain groups should be especially cautious. People taking medications that increase light or skin sensitivity, those with a history of skin cancer or serious eye disease, and individuals with photosensitive conditions are often advised by medical sources to consult a physician before using red light devices. In the pain and oncology worlds, MD Anderson emphasizes that red light and laser therapies are used as part of a broader pain‑management plan under specialist oversight, not as do‑it‑yourself substitutes.

University Hospitals points out that red light therapy is unlikely to repair major structural injuries such as significant ligament tears, which still require mechanical or surgical solutions. In those cases, red light may help manage inflammation or discomfort but will not reattach tissue.

Finally, it is worth acknowledging cost. University Hospitals notes that home devices typically begin just under about one hundred dollars and can run into the hundreds or thousands, and that treatments are often not covered by insurance. Given that, it makes sense to set realistic expectations. If the device represents a major financial strain, it may be better to focus on lower‑cost, higher‑impact strategies first.

Who Is Most Likely To Benefit, And Who Might Not

Sports recovery writers and clinics frequently highlight a few types of people who may see the clearest benefits from red light therapy around training. These include athletes and lifters who train intensely several days per week, whose soreness regularly lingers beyond roughly 48 hours, who are pushing close to their recovery limits, or who feel stuck at a strength or muscle plateau despite good sleep and nutrition. In these situations, even a modest improvement in recovery or workout quality can matter.

On the other hand, if you are a beginner lifting twice a week with generous rest days, your recovery reserves are probably large enough that the incremental benefit from red light is smaller. The same is true if your training or nutrition is inconsistent. In those cases, the smartest move is to put your effort into more basic levers before layering on advanced tools.

For people with chronic pain, tendon issues, or arthritis near the skin surface, early data summarized by WebMD and University Hospitals suggest that red light can sometimes reduce pain and stiffness and improve function, especially when inflammation is a big driver of symptoms. However, the quality of evidence ranges from low to moderate, and many trials are small. It is best to involve a healthcare professional if you are using red light in the context of chronic illness or rehabilitation.

FAQ

If I can only pick one, should I choose pre‑workout or post‑workout red light for muscle gain?

Based on the current body of evidence, if your primary goal is hypertrophy and you have to choose a single timing, pre‑workout is the more defensible choice. The clearest long‑term trials in healthy young men that reported extra muscle size and strength on top of training used red light immediately before each workout. That said, some studies show muscle growth with post‑training light, and recovery‑oriented benefits such as less soreness often come from post‑exercise protocols. If you value comfort, sleep quality, and pain reduction more than squeezing out a small edge in muscle size, you might reasonably favor post‑workout sessions instead.

Can I just use red light every day for as long as possible to get more results?

The research does not support a “more is always better” approach. Animal studies and human reviews on photobiomodulation describe a biphasic dose response, where too low a dose has no effect and too high a dose can negate benefits. Clinical and wellness protocols that report positive results generally use moderate, time‑limited sessions, often in the 10–30 minute range per area, a few times per week or up to several times per day for short periods during active healing. It is better to follow evidence‑informed, device‑specific guidelines and monitor how you feel than to dramatically exceed recommended exposure times.

Will red light therapy replace my warm‑up, stretching, or protein intake?

No. Independent analyses from Examine.com and expert commentary from University Hospitals are very clear that red light therapy should not be prioritized over established training, nutrition, and recovery strategies. Warm‑ups prepare your nervous system, joints, and soft tissues for load in ways light cannot. Adequate protein, carbohydrates, and total calories supply the raw materials for muscle growth. Sleep and stress management regulate hormones and repair. Red light can be a supportive modality layered on top of these pillars, but it will not compensate for skipping them.

In the end, muscles grow primarily from progressive tension, adequate fuel, and enough recovery. Red light therapy appears to offer a gentle nudge in the right direction for some people, especially when used before or around strength training, but it is not magic. If you decide to bring a red light panel into your home gym, treat it as one more thoughtful tool: integrate it around solid training, listen to your body’s feedback, and let the data from your own logbook guide whether it earns a permanent spot in your routine.