Best red light therapy settings for injury treatment and exercise recovery
- Maryke Louw
- Jun 21
- 11 min read
Updated: Jun 23
Red light therapy can be effective for treating many sports injuries and supporting post-exercise recovery. But each type of tissue (e.g. muscles, tendons) responds better to slightly different settings. And if you overuse it, it can actually slow healing! Read on to learn the ins and outs of how to use red light therapy at home for best results.
Remember, if you need help with an injury, you're welcome to consult one of our physios online via video call.
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In this article:
How does red light therapy work?
Red light therapy works by stimulating mitochondria – the energy-producing structures in your cells – using wavelengths of red or near-infrared light.
This increases the production of adenosine triphosphate (ATP), which fuels cellular repair. It also reduces inflammation, improves blood flow, and might reduce pain through changes in nerve activity and releasing endorphins.
In practical terms, the people in the white lab coats (who call it "photobiomodulation") have found benefits in especially pain reduction for certain types of injury, and speeding up healing for injuries closer to the surface. Studies have also shown that red light therapy helps with post-exercise recovery.
However, results vary depending on the wavelength, dose, timing, and the condition being treated (see below). Some studies have shown no effect, likely due to improper dosing or other treatment errors.
It's not a silver bullet
Red light therapy on its own isn't enough for injury recovery.
Hopefully it would be obvious to everyone that an uninjured person isn’t going to get stronger biceps by just using red light therapy on their upper arms while not doing a single bicep curl. It’s the same with a body part that has been weakened by an injury.
👉 So, while red light therapy has been shown to reduce pain and speed up healing, it doesn't actually strengthen tissue. For your injured body part to regain its full strength and endurance, you have to still follow a rehab plan that includes strengthening exercises.
Red light therapy risks and dangers
Red light therapy is low-risk when applied with proper dosage, timing, and precautions – but like most treatments, it’s not risk-free. Most studies report no serious adverse effects, and it’s approved by health authorities like the USA’s FDA for various therapeutic uses.
⚠️ The main risk is overexposure. Delivering too much energy can reduce effectiveness due to the biphasic dose-response – a phenomenon where too much light slows healing instead of helping it.
Repeated overtreatment may also cause temporary fatigue, dizziness, or skin irritation. (See below for dosage recommendations.)
Another concern is eye safety. Red and near-infrared light can damage the retina if you stare directly into a high-powered device, especially lasers. Always avoid direct eye exposure and use protective goggles if your device lacks built-in safety filters.
People with photosensitivity, or those taking photosensitising medications, should consult a doctor first. Additionally, red light therapy should not be used without medical supervision over active cancers, thyroid glands, or infected wounds because it might promote growth of these unwanted tissues or bugs.
Inflammation reduction: Good or bad?
Red light therapy reduces inflammation. But inflammation plays a crucial role in the early stages of injury healing as well as recovery after hard exercise.
🤷 So, won’t red light therapy work against healing and recovery in this regard❓
Excessive or prolonged inflammation can actually be harmful and might delay recovery from an injury or from exercise.
👍 Red light therapy doesn’t eliminate inflammation altogether. Instead, it modulates it – dampening excessive or chronic inflammation while still allowing the essential early-phase inflammatory processes to occur.
In a 2016 study, identical twins did a 12-week leg strengthening programme. One was given actual red light therapy on his quads after each strength session and the other was given “fake” red light therapy. The one who received the real therapy had bigger and stronger quads after the 12 weeks, even though he had less inflammation.
However, some evidence suggests daily red light therapy over many weeks might blunt adaptation in strength gains – alternating treatment days and non-treatment days or taking a week off red light therapy, say, every three weeks is advisable for strength athletes.
What type of red light therapy machine is best for home use?
Three types of device are used for red light therapy:
low-level lasers (LLLT),
LEDs,
and infrared heat lamps.
👍 Clinical research has historically focused on lasers, which deliver focused, coherent light that penetrates deeply. However, lasers are expensive, require professional handling, and are impractical for treating large areas (e.g. your quad muscles) at home.
👍 LED devices have become increasingly common in research and offer comparable benefits when used correctly. Unlike lasers, they emit non-coherent light, but can treat larger areas and are safe, affordable, and easy to use at home. Modern LED pads and panels are now used in clinical trials and often match or exceed laser effectiveness when treating injuries over large areas and/or that don’t require deep light penetration.
👎 Infrared heat lamps, on the other hand, are not supported by high-quality research. They produce heat, not targeted photobiomodulation effects, and are ineffective for cellular repair.
Conclusion: High-quality LED devices are the most practical and evidence-supported option for home use.
Here are three examples of LED red light therapy machines for home use. All of them are able to deliver the settings and dosages recommended below.
There are also hand-held red light therapy devices, which might be useful for targeted treatment, for example of injured tendons, but I could not find one that stated the irradiance (see below) and therefore I cannot recommend one with confidence.
Red light therapy settings and dosage
The correct settings and dosage are essential to get results from red light therapy. The four key parameters are:
Wavelength (nm):
This determines how deeply the light penetrates.
Red light (600–700 nm) is best for surface tissues like skin and the tendons in your hand.
Near-infrared light (780–950 nm) is invisible to the naked eye – it penetrates deeper and is more effective for muscles, ligaments, and thicker tendons, or ones that are not close to the skin.
Irradiance (milliWatt/cm²):
The light intensity at the skin's surface.
It tells you how much power is delivered per square centimetre.
A common target for soft tissue therapy is 15–30 mW/cm².
The further the light source is from the skin, the weaker the irradiance when the light hits the skin.
At an irradiance of more than 50 mW/cm² you start running the risk of overexposure and impaired healing.
⚠️ Very few red light therapy machine sellers on Amazon state the irradiance, so make sure you know what you’re getting in this regard if you buy a machine on Amazon or elsewhere.
Exposure time (minutes):
How long the light is applied to a single treatment area.
This time needs to be adjusted based on the irradiance to ensure an effective dose is delivered – the higher the irradiance, the shorter the time. (See below how to calculate this.)
Energy dose (J/cm²):
This is how much total light energy is delivered per square centimetre during a session.
It’s the result of the combination of light intensity (irradiance) and exposure time, and is what actually drives the biological effect.
In various studies, the best effects were achieved within the range of 3–10 J/cm².
How to calculate the energy dose
Two steps:
Convert irradiance from mW/cm² to W/cm² (1 mW = 0.001 W)
Multiply this by time in seconds
For example, to calculate the energy dose when the machine is set at an irradiance of 20 mW/cm² and you use it for 5 minutes over an area:
20 mW/cm² = 0.020 W/cm²
Multiply this by (5 x 60) seconds
So, 0.020 W/cm² x 300 seconds = 6 J/cm²
If you have the irradiance and energy dose and you want to calculate the time, divide the energy dose by the irradiance (in W/cm²). For example,
your irradiance setting is 20 mW/cm² and the energy dose is 5 J/cm².
So: 5 J/cm² ÷ 0.020 W/cm² = 250 seconds = just over 4 minutes per treatment spot.
👉 If, like me, you feel your 🧠 brain wants to go on ✈️ vacation when you look at all of these numbers and calculations, download our Red Light Therapy cheat sheet here. It simplifies things a lot!
Now, let’s see what are the best research-backed approaches for treating various types of injury at home with a red light therapy device, and then we’ll look at red light therapy for post-exercise recovery.
Tendon injuries
〰️ Light Frequency (Wavelength)
Effective range: 630–680 nm (red light) and 780–860 nm (near-infrared light)
Most commonly used in effective studies:
660 nm (red) – shallow penetration, suitable for surface tendons
810–830 nm (near-infrared) – deeper penetration for thicker tissues
💡 Light Intensity (Irradiance)
Effective range: 5–50 mW/cm² at tissue level
10–30 mW/cm² got the best results in research
⏱️ Energy Dose
Effective dose range: 4–10 J/cm² per session
Most tendon studies use 5–8 J/cm²
📅 Number of Sessions
Most research studies showing positive effects used:
2–3 sessions per week (do not do sessions on consecutive days)
Total: 10–15 sessions over 4–6 weeks
Considerations
Tendons are slow to heal – longer treatment periods are justified.
Target tissue depth matters: Near-infrared is better for deeper tendons.
Don’t exceed 10 J/cm² per session at the tissue site unless guided by clinical data – higher doses may reduce effectiveness (the biphasic dose-response effect).
Always follow device-specific calibration, as stated output may differ from actual irradiance at the skin.
I don’t recommend red light therapy as a standalone treatment for tendon injuries such as Achilles tendonitis or tendinopathy. Research has shown that it works best when combined with the recognised best treatment approach of relative rest and strengthening exercises.
Ligament injuries
〰️ Light Frequency (Wavelength)
Effective range: 630–680 nm (red light) and 780–860 nm (near-infrared light)
Most commonly used in effective studies:
660 nm (red) – effective for superficial ligaments (e.g. lateral ankle ligaments)
810–830 nm (near-infrared) – for deeper ligaments (e.g. MCL in the knee)
💡 Light Intensity (Irradiance)
Effective range: 10–30 mW/cm² at skin level
Most ligament-focused protocols use 15–25 mW/cm²
⏱️ Energy Dose
Effective dose: 5–8 J/cm² per session
📅 Number of Sessions
Effective clinical protocols generally follow:
3 sessions per week (not on consecutive days)
Total treatment duration: 4–6 weeks
Typical total sessions: 12–18
Considerations
Like tendons, ligaments are slow to heal – longer treatment periods are justified.
Early treatment (within 72 hours) improves outcomes for acute sprains.
Avoid overtreatment (>10 J/cm² per spot) to prevent slowing the repair process.
Eye safety is crucial, especially when treating ligaments near the face (e.g., jaw, cervical spine).
Muscle injuries
〰️ Light Frequency (Wavelength)
Effective range: 660–680 nm (red light) and 800–850 nm (near-infrared light)
Studies on muscle contusions and strains show better outcomes with near-infrared light due to deeper penetration.
Consider using 660 nm or dual-wavelength protocols for more superficial injuries.
💡 Light Intensity (Irradiance)
Muscle studies showing benefits generally used 20–25 mW/cm².
⏱️ Energy Dose
Effective dose: 4–10 J/cm², with most studies using 6–8 J/cm²
📅 Number of Sessions
Effective protocols for acute injuries typically follow:
Daily or every other day for the first 1–2 weeks (inflammation phase)
Then taper to 2–3×/week, and not on consecutive days, through recovery phase
Considerations
Early intervention: Best results occur when therapy starts within 24–48 hours post-injury
Avoid heating devices: Red light therapy should not generate heat – devices must stay in the low-power range
Adjust for tissue depth: Near-infrared light (830 nm) is necessary for muscle belly and fascia injuries
Treatment area: Cover the full injured region and slightly beyond margins to address inflammatory spread
Exercise recovery
Red light therapy can help with post exercise recovery by reducing fatigue, improving muscle repair, and shortening recovery time after intense training or competition, including endurance or strength-focused activity.
〰️ Light Frequency (Wavelength)
Effective range: 630–680 nm (red) and 800–860 nm (near-infrared)
Near-infrared penetrates deeper, especially helpful for large muscle groups (quads, glutes, hamstrings)
Research studies often used 660 nm + 850 nm together
💡 Light Intensity (Irradiance)
Effective range: 15–50 mW/cm²
Studies showing best results tend to use 20–30 mW/cm²
⏱️ Energy Dose
Studies have found that the effective range is 3–8 J/cm², depending on muscle size and depth
📅 Number and Timing of Sessions
When to treat: Studies show greatest benefit when red light therapy is applied immediately after exercise or within 30 minutes
Considerations
Avoid overtreatment: Doses >10 J/cm² per spot may reduce benefits
Hydration and rest still matter – red light therapy complements but doesn't replace core recovery practices
Adaptation caution: Some evidence suggests daily red light therapy over many weeks might blunt adaptation in strength gains – alternating treatment days and non-treatment days or taking a week off red light therapy, say, every three weeks is advisable for strength athletes.
Download the Red Light Therapy Guide
👉 We've simplified the advice in this article into an easy-to-read table. You can download the guide as a pdf with all the recommended red light therapy settings and dosages for tendon, ligament, and muscle injuries as well as for post-exercise recovery, by going to this page.
Final tips
For successful red light therapy at home:
Stay consistent: Missed sessions reduce effectiveness.
Use on clean, dry skin for best absorption.
Avoid sunscreen or lotion on the treatment area before sessions.
Check your device’s output: Ensure that the manufacturer lists actual irradiance (mW/cm²). And check the actual irradiance at skin level, not just the manufacturer specs.
Use dual frequency treatment if you’re not sure how deep the tissue is that you want to treat.
Keep a log: Track sessions and pain/recovery progress.
How we can help
Need more help with your injury? You’re welcome to consult one of the team at SIP online via video call for an assessment of your injury and a tailored treatment plan.
We're all UK Chartered Physiotherapists with Master’s Degrees related to Sports & Exercise Medicine or at least 10 years' experience in the field. But at Sports Injury Physio we don't just value qualifications; all of us also have a wealth of experience working with athletes across a broad variety of sports, ranging from recreationally active people to professional athletes. You can meet the team here.
About the Author
Maryke Louw is a chartered physiotherapist with more than 20 years' experience and a Master’s Degree in Sports Injury Management. Follow her on LinkedIn and ResearchGate.
