Red Light Therapy & Muscle Growth: The Science Explained

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.

As a red light therapy and targeted wellness specialist, I meet a lot of people who come in with the same hope: “Can red light therapy help me build muscle faster and recover better from my workouts?” The honest answer is nuanced. The biology is promising, some studies show real benefits, and many athletes feel better using it. At the same time, high‑quality evidence is mixed, and red light is nowhere near a magic shortcut.

This article walks through what we actually know about how red light therapy interacts with muscle tissue, what the research shows for strength and hypertrophy, and how you can use it thoughtfully at home or in a gym setting without wasting time or money.

What Red Light Therapy Is in a Fitness Context

Red light therapy in sports and fitness is typically a form of photobiomodulation. It uses low‑level red and near‑infrared light, usually in the range of about 630 to 850 nanometers, delivered by LEDs or low‑level lasers. The light is non‑ionizing and non‑UV, so it does not tan the skin or behave like a tanning bed.

Medical and sports sources such as Cleveland Clinic, ACE (the American Council on Exercise), and multiple sports performance clinics describe red light therapy as a noninvasive way to stimulate cellular activity, improve circulation, and reduce inflammation. Devices range from full‑body beds and large panels to smaller hand‑held wands, wraps, caps, and masks.

In athletic settings, the focus shifts from skin and hair to muscles, tendons, and joints. Clinics and fitness centers promote red light therapy as a way to support:

muscle recovery after hard training
small gains in strength or endurance when combined with exercise
reductions in soreness, stiffness, and joint pain

The key phrase here is “when combined with exercise.” Across the research notes, no credible source suggests that red light therapy builds muscle in the absence of training. It is framed as a possible ergogenic aid or recovery tool, not a stand‑alone muscle builder.

How Red Light Interacts With Muscle Tissue

Mitochondria and ATP: More Cellular Fuel

Multiple sources, including sports medicine clinics and scientific reviews, describe the same core mechanism. Red and near‑infrared light are absorbed by chromophores inside mitochondria, particularly an enzyme called cytochrome c oxidase. When this enzyme absorbs light, nitric oxide that is blocking the respiratory chain can be displaced, which improves oxygen use and increases ATP production.

FunctionSmart and other clinical sources note that under certain parameters, mitochondrial ATP output may increase substantially, in some cases reported as up to about 200 percent in experimental settings. More ATP means muscle cells have more chemical energy available for contraction, repair, and adaptation after training. This is the biological foundation for claims that red light therapy might support muscle performance and growth.

Blood Flow, Oxygen Delivery, and Vasodilation

Several fitness and rehabilitation sources, along with ACE and Stanford Medicine, describe red light as promoting vasodilation, the widening of blood vessels. This is thought to occur partly through nitric oxide–related pathways. When blood vessels dilate, local circulation increases, which can deliver more oxygen and nutrients to working or recovering muscles and help remove metabolic byproducts.

Articles from City Fitness, Fick PT & Performance, and the Physical Achievement Center highlight improved circulation and even the growth of new small blood vessels as potential benefits. Better blood flow is one of the proposed reasons red light may reduce soreness and support faster recovery after intense workouts.

Inflammation, Oxidative Stress, and Muscle Damage

Another key pathway is inflammation control. Sports performance clinics and review articles report that red and near‑infrared light can reduce pro‑inflammatory cytokines, boost endogenous antioxidant defenses, and decrease oxidative stress.

A large review on photobiomodulation in human muscle tissue summarizes animal and human studies showing reduced creatine kinase, lower markers of oxidative stress, and, in some protocols, less delayed onset muscle soreness (DOMS) after intense eccentric exercise. The randomized trial on LED therapy in resistance‑trained muscle found that participants receiving active light had smaller rises in muscle damage markers and reported less soreness than placebo.

This modulation of inflammation and oxidative stress creates an environment that may allow muscle fibers to repair more efficiently between training sessions.

Gene Expression and Muscle Remodeling

One of the most interesting pieces of evidence comes from a controlled trial that examined gene expression in muscle tissue after LED photobiomodulation combined with resistance training. Compared with placebo, the LED group showed:

increased expression of genes associated with muscle growth and regeneration, including myogenic regulatory factors and IGF‑related pathways
decreased expression of genes linked to muscle atrophy, such as myostatin and components of the ubiquitin–proteasome system

In plain language, red light shifted the molecular “conversation” inside muscle cells toward anabolism and away from breakdown, at least under the specific study conditions. This aligns with reports of greater hypertrophy and performance gains in that trial. However, it is important to remember that these findings come from a relatively small group of young, untrained adults and do not automatically generalize to all populations.

Red light penetrating muscle tissue to boost ATP for muscle growth and repair.

What the Research Says About Muscle Growth and Strength

Short‑Term Performance: More Reps, Sometimes

Several acute studies have tested red light therapy applied just before exercise. A concise evidence review from Examine highlights that in certain eccentric resistance exercises, such as biceps curls or knee extensions, red light exposure immediately before the session has been associated with a small increase in repetitions to failure.

A 2015 systematic review and meta‑analysis of randomized, placebo‑controlled trials found that phototherapy applied before exercise improved key performance measures like maximum repetitions, speed, endurance, and time to exhaustion compared with placebo. Some endurance studies reported that combining treadmill training with light therapy led to improvements in oxygen uptake and endurance occurring about three times faster than training alone.

However, Examine and Stanford Medicine both emphasize that these ergogenic benefits are context‑dependent and not consistently replicated. Many of the more positive findings come from a limited number of research groups and small samples. So while there is real evidence that red light can sometimes enhance short‑term performance, it is not a guaranteed boost for every athlete or workout.

Long‑Term Hypertrophy: Young Adults vs Older Adults

For muscle growth, the most direct evidence comes from resistance training studies where one group receives photobiomodulation and another does not. The LED trial in untrained young adults reported that training combined with red/near‑infrared LED therapy led to significantly greater increases in muscle size and strength than training plus placebo. Participants in the active group gained more cross‑sectional area and improved maximal strength and power to a greater degree.

Sports medicine summaries, including those cited by Synergy Physical Therapy and DegreeWellness, describe similar findings from other trials: larger improvements in muscle thickness, strength (such as leg‑press torque), and overall performance when red or near‑infrared light is combined with structured resistance training. Some groups observed more than 50 percent greater increases in muscle size or strength versus exercise alone.

Yet this is where the nuance matters. Examine notes that when similar protocols were used in older men, adding red light therapy to strength training did not produce extra gains in muscle size or strength. A study in older women applying red light after strength training did not improve muscle strength either, and muscle size was not reported.

Taken together, the best conclusion from the current notes is that red light therapy can enhance hypertrophy and strength in some settings, particularly in younger, untrained or recreationally trained individuals, but it does not reliably do so across ages and populations. The heavy reliance on a small body of positive studies, often from the same research teams, is another reason to keep expectations modest.

Recovery, DOMS, and Training Frequency

Many people turn to red light therapy not just for bigger muscles but for less soreness and faster recovery. Some of the evidence supports this, but again, it is not uniform.

The controlled LED trial mentioned earlier found that participants who received active light therapy had smaller increases in markers of muscle damage and reported lower soreness after training sessions than the placebo group. Several clinical sports centers report similar real‑world observations of reduced DOMS, faster perceived recovery, and the ability to train more frequently.

The broader review of photobiomodulation in muscle tissue reports that certain protocols applied before or after exercise reduced soreness, preserved muscle force, improved range of motion, and lowered creatine kinase levels up to 72 hours after damaging exercise. However, other protocols, sometimes with different wavelengths, doses, or treatment locations, did not show meaningful effects on soreness or performance.

This pattern is echoed by Athletic Lab’s summary of a systematic review: some individual studies show less DOMS with pre‑exercise red light, but overall evidence for substantial soreness reduction is inconclusive. Examine similarly notes that red light therapy does not consistently reduce post‑exercise muscle soreness across studies.

From a practical standpoint, this means red light therapy may ease soreness and help you feel ready for your next session, but you should not count on it to eliminate DOMS altogether or assume that more light automatically equals better recovery.

Endurance and High‑Intensity Exercise

Endurance and high‑intensity performance are closely linked to mitochondrial capacity and oxygen use, which makes them logical targets for red light therapy.

The photobiomodulation review, DegreeWellness summary, and ACE’s expert article all describe studies in which pre‑exercise red or near‑infrared light improved time to exhaustion, running economy, and cycling performance, and led to faster endurance improvements when combined with training. In some treadmill studies, athletes combining phototherapy with training saw endurance gains occur several times faster than the group doing training alone.

At the same time, Examine and Stanford Medicine point out that anaerobic performance benefits are not consistently replicated, and sports medicine experts interviewed by Stanford remain unconvinced that red light therapy currently has a strong evidence base for enhancing athletic performance in general.

The evidence as a whole suggests that under specific conditions and with well‑chosen parameters, red light therapy can modestly enhance endurance and high‑intensity performance, but results are heterogeneous, and this should not be viewed as a guaranteed performance enhancer.

Research findings on muscle growth and strength gains for fitness training, highlighting hypertrophy.

Where Red Light Therapy Fits in a Real‑World Training Plan

A Supportive Tool, Not a Shortcut

Retro Fitness and other fitness brands are explicit about this: red light therapy is a recovery “accelerator” that works best alongside the fundamentals, not instead of them. The fundamentals remain progressive resistance training, adequate protein, sufficient calories, hydration, and high‑quality sleep.

In the research notes, even the most enthusiastic clinical sources present red light therapy as an adjunct. Examine concludes that, given mixed evidence and limited high‑quality trials, red light therapy cannot be recommended as a dependable way to enhance muscle growth, strength, performance, or recovery for the general exercising population. ACE likewise describes it as a promising but still‑emerging modality with no standardized dosing guidelines.

From a wellness specialist perspective, I encourage people to see red light as a tool that might give an extra few percentage points of benefit if everything else is already dialed in, not as a replacement for the basics.

Potential Benefits You Might Notice

When red light therapy is well‑matched to your training, overall health, and budget, the changes you notice are often subtle at first. Athletes and active adults commonly report feeling less stiffness the day after heavy training, a smoother transition between hard sessions, and easier warm‑ups. Some endurance athletes feel their legs “come back” more quickly between intervals or races.

Clinics like the Physical Achievement Center and Fick PT & Performance also see joint comfort improve over several weeks of consistent use, likely because of better tissue quality, collagen support, and reduced inflammation in tendons and ligaments that take a beating during training.

City Fitness and other practitioners highlight potential sleep improvements when red light therapy is used consistently in the evening, possibly through circadian and hormonal effects. While sports and sleep experts interviewed by Stanford remain cautious about these claims, better sleep alone can indirectly support muscle growth and recovery, so timing your sessions in a calming bedtime routine can be a reasonable strategy.

When It May Not Help Much

The notes also make it clear that red light therapy has limits. University Hospitals sports medicine experts do not expect red light to repair structural injuries like ligament tears or to reverse advanced osteoarthritis. It is most promising for inflammatory and more superficial musculoskeletal issues and as a support for recovery, not as a fix for major mechanical problems.

Evidence is also weaker for older adults looking for muscle growth. Long‑term studies in older men and women have not consistently shown extra strength or hypertrophy gains when red light is added to strength training. And Stanford Medicine experts emphasize that, for now, data for athletic performance and sleep are much weaker than for hair or skin applications.

If you are already highly trained and hoping for dramatic muscle gain solely from adding red light, the current evidence does not support that expectation. It is more realistic to hope for modest support in recovery and possibly a small boost in training quality over time.

Practical Guidelines for Using Red Light Around Workouts

Because there are no universally accepted FITT (frequency, intensity, time, type) guidelines for exercise recovery, any practical advice has to stay close to what has actually been used in research and clinical protocols.

Timing: Before vs After Exercise

Sports performance clinics and reviews describe two main strategies: pre‑conditioning and post‑exercise recovery.

The Physical Achievement Center notes that using red or near‑infrared light about 15 to 30 minutes before intense training may “prime” muscles at the cellular level, potentially reducing metabolic stress and delaying fatigue. Several trials cited by DegreeWellness and Synergy Physical Therapy applied light immediately before strength or endurance sessions and observed improved performance or faster adaptation.

For recovery, FunctionSmart and similar clinics highlight sessions delivered within about two to four hours after training, aiming to support tissue repair, circulation, and clearance of metabolic waste. Some research applied light between sets or shortly after exercise and reported less performance decline and lower muscle damage markers.

A practical way to translate this into daily life is to pick one main use case to start. For strength training days, consider pre‑session exposure if your goal is performance. For especially hard or high‑volume days, a post‑session window may be more appealing for recovery. There is no strong evidence that more sessions in both windows automatically provide better results.

Frequency and Session Length

Across gym chains and clinics, recommended session lengths for full‑body or large‑area treatment typically fall in the 10 to 20 minute range per area, which aligns with parameters described by FunctionSmart, Retro Fitness, and PhysioPedia’s evidence summary. Retro Fitness suggests sessions of roughly 10 to 20 minutes, three to five times per week, and emphasizes consistency over occasional long exposures.

Research‑oriented summaries mention a range of energy densities delivered over five to twenty minutes per muscle group, reinforcing the idea that shorter, regular treatments are generally preferred to sporadic marathon sessions.

Consistent use over weeks is important. Multiple sources, including UCLA Health and University Hospitals, note that benefits from red light therapy, whether for skin, hair, or musculoskeletal issues, tend to appear gradually and require ongoing sessions. Early changes might be reduced stiffness or soreness; more visible strength or endurance changes, when they occur, tend to show up after two to four weeks of steady use.

Device Choice and Dose Considerations

Cleveland Clinic, UCLA Health, and Stanford Medicine all point out that devices used in clinical or research settings tend to be more powerful and more carefully calibrated than most consumer products. At‑home panels, wands, caps, and masks vary widely in power output, wavelength, and treatment time. Some devices are cleared by the US Food and Drug Administration primarily for safety, not necessarily for proven clinical effectiveness.

This does not mean at‑home devices are useless, but it does mean expectations should be realistic. University Hospitals suggests starting with a home device when it is financially reasonable and emphasizes that the main risk is often to your wallet, not your health, when devices are used as directed.

From an at‑home wellness perspective, it is wise to:

choose a device that clearly specifies wavelength in the 630 to 850 nanometer range
follow distance and time instructions closely rather than improvising longer sessions
keep a simple log of when and how you use it, along with notes on soreness, sleep, and training performance

PhysioPedia’s research‑oriented summary also recommends documenting parameters like wavelength, session duration, and treatment distance, because consistency over time is essential if you want to evaluate whether red light is doing anything meaningful for you.

Red light therapy workout guidelines: muscle warm-up, recovery, and safety tips.

Safety, Side Effects, and Cost

Cleveland Clinic, UCLA Health, University Hospitals, and Stanford Medicine converge on one point: short‑term, directed red light therapy appears generally safe, noninvasive, and low risk when used correctly. Unlike ultraviolet light, it does not use wavelengths known to cause skin cancer.

However, all of these sources also highlight important caveats. Overuse, incorrect use, or directing light into unprotected eyes can cause damage, and long‑term safety data are still limited. People with photosensitive disorders, those taking photosensitizing medications, and pregnant individuals should be especially cautious and consult a physician before using light therapy devices.

There is also a clear distinction between realistic medical expectations and aggressive marketing. Stanford experts note that evidence is relatively robust for hair regrowth and modest wrinkle reduction, but much weaker or absent for popular claims such as broad athletic performance enhancement, sleep improvement, or treatment of many systemic conditions.

Cost and time are real considerations. Cleveland Clinic and University Hospitals remind patients that red light therapy is often not covered by insurance and may require multiple sessions per week for weeks or months. Active Wellness Center gives an example of pricing in a fitness setting, with packages like about $40 per session or roughly $100 per month for up to a dozen sessions. Home devices can start under about $100 for small handhelds and climb into the hundreds or thousands of dollars for larger panels or full‑body systems.

In practice, I encourage people to weigh these costs against the relatively modest and uncertain benefits for muscle growth alone. Red light therapy can be worthwhile if you also value its potential effects on joint comfort, skin, sleep, or general well‑being and if the financial investment feels sustainable.

Red light therapy: safety, side effects, and cost considerations for muscle growth.

Summary Table: Muscle Growth and Red Light Therapy

Goal or Claim	Typical Use in Studies/Clinics	What the Evidence in the Notes Suggests
Increase reps or short‑term performance	Light applied immediately before strength or endurance sessions	Small, context‑dependent benefits; not consistently replicated
Enhance hypertrophy and strength	Pre‑ or post‑exercise light plus progressive resistance training	Clear benefits in some young adult trials; no added effect in some older adults; evidence limited overall
Reduce DOMS and speed recovery	Light before or soon after intense or eccentric exercise	Some protocols reduce soreness and damage markers; others show no effect; overall mixed results
Improve endurance and time to exhaustion	Pre‑exercise light in treadmill, cycling, or running protocols	Several positive studies; broader experts remain cautious and call for more research
Support joint comfort and pain relief	Repeated sessions targeting tendons, joints, and affected muscles	Early promise for tendinopathies and musculoskeletal pain; used as adjunct, not stand‑alone cure
Replace training or fix structural injuries	Light alone without load or in place of surgery	No evidence that red light builds muscle without training or repairs major mechanical damage

FAQ

Can red light therapy build muscle if I do not work out?

Based on the research summarized here, no. In trials where red light therapy enhanced muscle size or strength, it was always combined with structured resistance training. The light appears to support cellular processes that help muscles respond to training stress, not to stimulate muscle growth independently in the absence of that stress.

Is it better for younger or older adults?

The strongest positive findings for muscle hypertrophy and strength come from studies in younger, generally healthy men doing structured resistance training. When similar protocols were tested in older men and women, researchers did not consistently find additional gains in strength or muscle size. That does not mean older adults cannot benefit at all; some evidence suggests improvements in pain, mobility, and endurance. It does mean that expectations for extra muscle growth from red light therapy alone should be conservative in older populations.

How long does it take to see results?

Most clinical and research‑based discussions emphasize that red light therapy is not a “one and done” treatment. For musculoskeletal benefits, many athletes and patients notice subtle changes such as reduced stiffness or soreness after a few sessions, with more meaningful improvements in recovery or performance metrics appearing after two to four weeks of consistent use. For skin and hair applications, dermatology sources often mention several months of regular treatment. If you do not notice any difference after a few weeks of faithful use, it is reasonable to reassess whether the time and money are well spent.

Is at‑home red light therapy worth it for muscle growth?

At‑home devices can be a reasonable entry point, especially if they are not a major financial strain and if you appreciate potential benefits beyond muscle growth, such as joint comfort or skin improvements. However, consumer devices vary widely in power and quality, and large medical centers like Cleveland Clinic and Stanford Medicine note that effectiveness is difficult to predict. If you choose a home device, treat it as an experiment: commit to a consistent protocol for several weeks, track how you feel and perform, and be prepared to adjust or discontinue if you do not see meaningful benefits.

Red light therapy is an intriguing intersection of light, biology, and performance. Mechanistically, it makes sense that targeted red and near‑infrared wavelengths could support muscle energy production, recovery, and adaptation. A number of well‑designed but relatively small studies show real, measurable benefits, especially in younger individuals training hard. At the same time, larger institutions and independent reviewers consistently remind us that the evidence is still limited, inconsistent, and heavily dependent on specific protocols.

As a red light therapy wellness specialist, my role is to help you use this tool in a grounded, practical way. If your training, nutrition, and sleep are dialed in, and you are curious about adding a low‑risk modality that might make recovery feel smoother and training slightly more effective, red light therapy can be worth trying with clear eyes and healthy skepticism. Start conservatively, stay consistent, listen closely to your body, and always coordinate with your healthcare team when you are managing pain or medical conditions alongside your fitness goals.