Red Light Therapy for Muscle Growth: What the Training Trials Show

Red light therapy for muscle growth has its best support as an add-on to lifting, not as a stand-alone method: in small training trials in young men, near-infrared light on the thighs at each session gave larger strength gains and, in some studies, more muscle thickness than training alone. Below: the muscle-size studies and their numbers, the two-person twin study behind the 20% figure, timing, wavelengths, dose, trial schedules, what matters more than light, safety and a panel routine.

Key takeaways

• In an 8-week trial of 30 young men, summed quadriceps thickness rose 15.4% with 810 nm laser light before eccentric training, against 9.4% with training alone. Baroni, 2015
• In a 12-week placebo-controlled trial of 48 men aged 18 to 35, light before each leg session gave greater strength gains than light after, light both before and after, or placebo. Vanin, 2016
• The widely quoted 20% gain in thigh muscle volume comes from a two-person study of identical twins, against 5% in the twin who had placebo light. Ferraresi, 2016
• A 2018 review of 39 trials with 861 people found positive muscle results across 655 to 950 nm, with evidence quality rated very low to moderate. Vanin, 2018
• Across 49 trials of resistance training, protein supplements added 0.30 kg of fat-free mass, with gains levelling off at about 1.62 g of protein per kg of body weight a day. Morton, 2018

Does red light therapy for muscle growth work?

In some small trials, yes, as an add-on: young men who had light on their thighs at each session gained more strength, and in a few studies more muscle thickness, than men who trained without it. Every study that measured muscle size added light to a resistance programme, and the training groups grew too.

A 2016 review gathered 46 studies with 1,045 participants, using laser probes, LED clusters and flexible LED arrays in red, near-infrared and mixed wavelengths. J Biophotonics review, 2016 Its authors wrote that the evidence suggests light can increase the muscle mass gained from training. They also reported less inflammation and oxidative stress in muscle biopsies.

That review is narrative, so it gives no pooled figure. In older adults, a 2026 meta-analysis of 11 trials found no clear extra strength gain from light over training alone. Chen, 2026

How much extra muscle did lifters gain in the light trials?

In one 8-week trial, summed quadriceps thickness rose 15.4% with light against 9.4% with training alone. In a 12-week trial, the difference in thigh perimeter was too small to count as significant.

Study	Who	Light	Timing	Weeks	Muscle-size result
Baroni, 2015	30 young men, 10 per group	810 nm laser, 240 J in total	Before each session	8	Summed quadriceps thickness +15.4% with light, +9.4% training only
Ferraresi, 2011	36 young men	808 nm laser, 50.4 J over 140 seconds	Immediately after	12	Thigh perimeter +4.52% with light, +2.75% training only, not significant
Ferraresi, 2016 (twins)	2 identical twin men, aged 19	850 nm LED array, 75 J in 15 seconds	Immediately after	12	Thigh volume on MRI +20% with light, +5% placebo

In Baroni's trial, the extra gain showed in the summed thickness of the quadriceps, not in each muscle on its own. Baroni, 2015

Ferraresi's men did the leg press at 80% of their one-repetition maximum (1RM). Ferraresi, 2011 Thigh perimeter is a tape measure, a rough guide to muscle size.

Both trials compared light plus training with training alone, without a placebo light. These small studies are the main basis for red light therapy muscle hypertrophy claims in young lifters.

What does the 20% twin study show, and why does it need context?

One 19-year-old twin had 850 nm LED light after each session and gained 20% thigh muscle volume on MRI, against 5% in his brother on placebo. It is a two-person study, so it shows what is possible rather than what to expect.

The twins trained 3 times a week for 12 weeks: leg press at 80% of 1RM and leg extension at 50%. Ferraresi, 2016 A flexible array of 50 LEDs sat in contact with the skin over both quadriceps for 15 seconds.

• Volume: 2937 to 3523 cm³ in the LED twin, 3152 to 3316 cm³ in the placebo twin.
• Leg press 1RM: +53% with LED, +28% with placebo.
• Leg extension 1RM: +37% with LED, +20% with placebo.
• Recovery: creatine kinase, a marker of muscle damage, and soreness were lower in the LED twin.
• Genes: myostatin, a protein that limits muscle growth, fell more in the LED twin.

The authors called for studies with more volunteers.

Should you use red light before or after lifting for muscle gains?

Before, if you can manage it: in the one trial that compared timings inside a strength programme, light before each session with placebo after gave the largest gains. After training is the fallback, and two of the size studies applied light straight after.

The 48 men in the timing trial did leg extension and leg press for 12 weeks. Vanin, 2016 The light came from clusters of 905 nm laser diodes with 875 nm and 640 nm LEDs. Light before training beat light after, light both before and after, and placebo for peak torque and 1RM in both exercises.

Training trials applied light immediately before the session. Field trials in sport used it about 20 to 40 minutes before play, as our red light therapy for athletes guide explains.

A practical fit: 10 to 15 minutes on the muscles you are about to train, then your warm-up. Our article on red light therapy before or after a workout covers the timing in more depth.

Does red light add strength (1RM) as well as size?

In young men, the strength results have been more consistent than the size results. Leg press 1RM rose 55% with light after each session, against 26% with training alone, over 12 weeks.

That trial used 808 nm laser light on both quadriceps. Ferraresi, 2011 Only the light group improved on the isokinetic tests.

• Isometric peak torque: +20.5% with light before training, +13.7% with training alone. Baroni, 2015
• Eccentric peak torque: +32.2% with light, +20.0% with training alone.
• Pooled trials: the 2018 review found "some effect in favor" of light for repetitions, time to exhaustion and peak torque. Vanin, 2018

Strength gains across all trials are not yet conclusive, so log your lifts and judge by your own numbers.

Which wavelengths did the muscle growth trials use?

Mostly near-infrared: most training trials used 808 to 810 nm lasers, and the twin study used 850 nm LEDs. A 2018 review found positive results across 655 to 950 nm.

The timing trial added 640 nm red to 875 nm and 905 nm near-infrared. Vanin, 2016 Near-infrared passes deeper into tissue than red, which suits large muscles such as the quadriceps.

Our panel's 810, 830 and 850 nm channels sit closest to the trial wavelengths. Its 660 and 670 nm red channels sit at the lower end of the review's range. See 660 nm vs 850 nm for how the two bands differ.

Do LED panels work for muscle growth, or only lasers?

The closest evidence comes from lasers and LED arrays placed on the skin, mostly for seconds to a few minutes per site. The one size study with LEDs used an 850 nm array in skin contact for 15 seconds after each session.

All the devices in the 2016 review delivered light from outside the body, on the skin over the working muscle. J Biophotonics review, 2016 A panel lights a whole thigh from a short distance, so home use follows the pattern of the trials: near-infrared with red, on the trained muscle, at each session, for weeks.

Is a longer session better for red light therapy muscle hypertrophy?

No: in muscle studies, more light energy did not mean more effect. In a placebo-controlled trial of 28 soccer players, 10 J and 50 J per site helped strength recovery while 30 J showed no differences.

That trial used 810 nm light at 6 sites on the quadriceps before eccentric exercise. Photomed Laser Surg, 2016

• 50 J per site: higher maximal strength from just after exercise to 24 hours.
• 10 J per site: higher maximal strength from 24 to 96 hours.

The 2018 review found positive results most often with 20 to 60 J for small muscle groups and 60 to 300 J for large ones. Vanin, 2018 Our guide to how much red light therapy is too much explains this dose curve.

How many weeks of training with light did the trials run?

Between 8 and 12 weeks, with light at every training session on the trained thigh muscles. The twin study used 3 sessions a week.

Study	Wavelength	Dose or time	Timing	Sessions a week	Weeks
Baroni, 2015	810 nm laser	240 J in total	Before	Not stated in abstract	8
Vanin, 2016	905 nm laser, 875 and 640 nm LEDs	Not stated in abstract	Before gave the best result	Not stated in abstract	12
Ferraresi, 2011	808 nm laser	50.4 J over 140 seconds	Immediately after	Not stated in abstract	12
Ferraresi, 2016 (twins)	850 nm LED array	75 J in 15 seconds	Immediately after	3	12

All applied light on the skin over the muscle. Plan a block of at least 8 weeks and compare your training log at the start and the end.

Can red light replace protein, sleep or progressive overload?

No. Every muscle-size study added light to a lifting programme, and the training did most of the work.

The NHS advises strengthening activities "on at least 2 days a week", working the legs, hips, back, abdomen, chest, shoulders and arms. NHS Each set should go to the point where you need a short rest.

A 2018 meta-analysis pooled 49 trials with 1,863 people, each with at least 6 weeks of resistance training. Morton, 2018 Protein supplements added 0.30 kg of fat-free mass and 2.49 kg to 1RM.

In order of impact:

• Progressive training: at least 2 strength days a week, adding load or reps over time.
• Protein: gains levelled off at about 1.62 g per kg of body weight a day in total.
• Sleep and rest days: muscles adapt between sessions.
• Light: an optional add-on at training sessions.

Light on the skin is not a hormonal route either: as our article on red light therapy for men notes, no controlled study in men shows it raises testosterone.

Who should not use a red light panel for training, and when should you wait?

Skip the panel if any of our precautions apply, and give a freshly pulled or strained muscle 2 to 3 days before using light on it. Dark or brown urine with muscle pain, swelling or weakness after hard training needs urgent medical care, not light.

Our precautions rule the panel out:

• Pregnancy: while pregnant, breastfeeding or preparing for pregnancy.
• Seizures: epilepsy or seizures triggered by light.
• Thyroid: a thyroid condition or thyroid medication.
• Light sensitivity: photosensitising medication, or being photosensitive.
• Skin: broken skin or an open wound on the area, sunburn on the body in the past 2 weeks, or Fitzpatrick skin types V or VI.
• Sleep: not for use while asleep or by anyone unconscious.

If you take any medicine, check with your pharmacist or doctor before using the device. See a doctor or physio for a suspected muscle tear, and see our red light therapy for muscle pain guide for other warning signs.

Cleveland Clinic advises you to "shield your eyes for protection". Cleveland Clinic Wear the included goggles, keep your eyes closed and never look into the panel. Keep it on the muscles and away from the groin.

How do you use a Kivorla panel alongside resistance training?

Use it on training days, on the muscles you are about to train, for 10 to 15 minutes per area shortly before the session, then warm up. Place it at 6 inches for a smaller muscle group such as a calf, forearm or upper arm, and 12 inches for the thighs or back.

The 9-Spectrum Red Light Therapy Panel carries 480, 590, 630, 660, 670, 810, 830, 850 and 1060 nm, each dimmable from 1 to 100% on the controller.

• Position: hang it on a door or wall with the included door hook, pulley, hanging cables and screws, or stand it upright on the floor. For the upper back or shoulders, hang it at the right height and stand with your back or side to it.
• Distance: 6 inches for a calf, forearm or upper arm; 12 inches for the thighs, back or chest. The front and back of the thighs are two separate sessions.
• Channels: red and near-infrared on (630, 660, 670, 810, 830, 850 and 1060 nm); 480 and 590 nm off.
• Mode: continuous light, as in the twin study.
• Timer: 10 to 15 minutes per area. If no time is set, the panel stops at 5 minutes. The surface stays at or below 40°C.
• Skin: bare, clean skin, as clothing blocks light. If the skin feels hot, dim the near-infrared channels or step back.
• Eyes: goggles on and eyes closed for every session.
• Rhythm: sessions on training days for the trained muscles, about an hour of light a week, for a block of 8 to 12 weeks.

The trials gave small, fixed doses through probes or arrays on the skin. To stay nearer that studied range, use 10 minutes rather than 15, turn the channels down from 100%, or step back to 12 inches. Leave at least 6 hours between 30-minute sessions.

The 4-Wavelength mask is a face-only shell with a red mode and a blue mode, and it is not designed for muscle sessions.

Standard shipping to the US, UK and Germany is free. Read the precautions before ordering. Under our return and refund policy, returns are accepted within 30 days: an unopened device with its seals intact is refunded less a 10% restocking fee, and an opened device that is undamaged and complete is refunded less 20%.

Kivorla devices are general wellness devices, not medical devices, and are not intended to treat muscle loss or any disease. Speak to a doctor before training hard if you have a health condition, and see a doctor or physio for a suspected muscle tear.