Muscle Light Therapy

One lesser-known area of the body studied in light therapy research is muscle tissue. Human muscles have highly specialized energy production systems, designed to supply energy both for sustained low-intensity activity and for short bursts of high-intensity effort. In recent years, research in this field has surged, with numerous high-quality studies published each month. Red and infrared light have been widely researched for various conditions, such as joint pain and wound healing, likely due to their potential to affect cells on a fundamental energetic level. But can light penetrate muscle tissue and have beneficial effects? In this article, we explore how light interacts with muscle systems and the potential benefits it may offer.

How Might Light Affect Muscle Function?

To understand how light might influence muscle tissue, it’s important to first grasp how muscle tissue functions. Energy is essential for all cells, but this is especially evident in muscle tissue, which is responsible for movement. Muscles rely on energy generation and usage to facilitate movement. Anything that enhances this energy production could have significant benefits.

The Mechanism of Light Therapy

Light therapy operates through a well-understood mechanism in almost any cell that contains mitochondria—the organelles responsible for energy production. The key players here are Cytochrome C Oxidase and Nitric Oxide. The hypothesis is that red and near-infrared light help mitochondria optimize cellular respiration, leading to increased production of CO2 and ATP (the cell’s energy). This effect would theoretically occur in nearly every cell of the body, except for cells without mitochondria, such as red blood cells.

The Muscle-Energy Connection

Muscle cells are particularly rich in mitochondria to meet their high energy demands. This is true for skeletal muscle, cardiac muscle, and smooth muscle found in internal organs. While the density of mitochondria in muscle tissue varies between species and different parts of the body, all muscle tissue requires significant energy to function. This abundance of mitochondria makes muscle tissue an appealing target for light therapy research, possibly even more so than other types of tissue.

Muscle Stem Cells – Can Light Enhance Growth and Repair?

Myosatellite cells, a type of muscle stem cell involved in muscle growth and repair, may be a key target for light therapy—perhaps even the primary target responsible for its long-term effects. These satellite cells become active in response to physical strain, such as from exercise or injury, and this activation process could potentially be enhanced by light therapy. Like other stem cells in the body, myosatellite cells act as precursors to regular muscle cells. Normally in a dormant state, they become active and differentiate into either new stem cells or fully functional muscle cells during the healing process after injury or muscle stress.

Recent studies suggest that mitochondrial energy production is a crucial regulator of stem cell activity, determining their function, efficiency, and growth rate. Since light therapy is believed to promote mitochondrial function, there is a clear mechanism that could explain how light therapy might enhance muscle growth and repair by boosting the activity of these muscle stem cells.

Inflammation

Inflammation often accompanies muscle damage or stress, and some researchers suggest that light therapy may help reduce inflammation when used properly. By increasing CO2 levels, light therapy may inhibit the release of inflammatory cytokines and prostaglandins, potentially leading to more efficient muscle repair and less scarring or fibrosis.

Thyroid Hormones and Muscle Performance

Thyroid hormones, often considered the body’s master regulatory hormones, play a major role in cellular energy production, which is crucial for both muscle performance and recovery. Given this connection, studies have explored the effects of near-infrared light on the thyroid gland to determine if it can help normalize thyroid hormone levels, potentially enhancing muscle performance. For more information on thyroid light therapy, you can read further here.

Sleep Improvement

Improved sleep is one of the most commonly reported benefits of red light therapy, with several studies supporting this claim. Since deep, restorative sleep is critical for muscle recovery—something athletes and bodybuilders strongly emphasize—any improvement in sleep quality can positively impact muscle function and healing.

Testosterone Boost

Some researchers and animal studies suggest that red light therapy, when applied near the testes, may increase testosterone levels in men. This hormone is well known for its role in boosting muscle strength, size, and performance, making it a potential tool for enhancing athletic outcomes. You can read more about this topic in our dedicated blog post.

The Potential Benefits of Light Therapy on Muscle Function

Light therapy has been studied in a wide range of individuals and animals, from athletes and bodybuilders to those with muscular injuries or disorders. It has even been researched in animals like horses and dogs, particularly in competitive environments. Some key muscle-related effects of light therapy include:

Hypertrophy: The increase in muscle size resulting from exercise, known as hypertrophy, has been studied alongside light therapy with promising results. In muscle tissue, hypertrophy is an adaptive response that allows for greater force generation with less fatigue. This increase in muscle mass and strength is highly desired by bodybuilders and anyone looking to improve their physique.

Hypertrophy and Muscle Size Gains with Light Therapy

Some limited studies suggest that using near-infrared light before weight training may significantly improve muscle hypertrophy and size gains compared to performing the same exercises without light therapy. In one study involving untrained individuals, those who combined weight training with light therapy saw double the muscle size gains over an 8-week period compared to those who trained without light therapy. This makes light therapy a potentially valuable tool for personal trainers, elite athletes, or even regular individuals—particularly after periods of inactivity—by enhancing early progress and providing long-term benefits. While this study focused on untrained people, there is reason to believe it could benefit even highly trained athletes, giving them an additional edge in their exercise results.

Strength – Can Light Therapy Help You Get Stronger?

As mentioned earlier, light therapy may interact with both myosatellite cells and regular muscle cells by improving energy production. This could potentially result in an immediate boost in strength and endurance by enhancing regular muscle cell function, and a long-term strength increase by stimulating myosatellite cells, especially when combined with exercise.

One-Rep Max and Strength Gains

Studies examining one-rep max strength (the maximum amount of weight lifted in a single repetition) show that light therapy, particularly 850nm LED treatment, can improve strength gains compared to placebo treatment. These studies often measure peak torque, or the maximum force generated during a specific movement, and consistently demonstrate that light therapy in combination with exercise leads to greater strength improvements than exercise alone. The results have been significant across various studies, to the extent that international sports regulatory bodies are considering whether light therapy should be allowed in competitive settings.

Reducing DOMS and Muscle Soreness with Light Therapy

Several studies indicate that light therapy may reduce the severity and accelerate the recovery of delayed onset muscle soreness (DOMS)—the muscle discomfort experienced after intense workouts. DOMS is believed to be caused by microtrauma to muscle fibers, leading to an influx of calcium into the cells, which disrupts cellular respiration and contributes to muscle damage and inflammation. Light therapy appears to help alleviate these symptoms, potentially speeding up the recovery process and reducing post-workout soreness.

Calcium and Muscle Recovery with Light Therapy

For muscle recovery to occur, calcium must be transported out of the cell, which requires energy in the form of ATP. Light therapy is hypothesized to accelerate ATP production, which could speed up the overall muscle recovery process by helping cells expel calcium and produce CO2, reducing inflammation in the process. This would, in theory, lessen both the severity of delayed onset muscle soreness (DOMS) and the time needed for full recovery.

Light Therapy for Injury and Strain Recovery

Several studies suggest that light therapy, when applied correctly, may positively influence recovery from muscle injuries. One major concern with muscle injuries is the development of fibrosis or scar tissue, similar to how the skin scars after injury. This scar tissue can alter muscle function, reduce mobility, and cause chronic pain. Light therapy could help prevent this scarring by reducing inflammation and promoting the healing process at a cellular level. The therapeutic effects of light therapy have been observed in various studies, not just for muscle injuries but for wounds on the skin, brain trauma, and even broken bones.

Ideal Light for Muscle Therapy

Infrared vs. Red Light Penetration

One of the main challenges in muscle light therapy is ensuring the light penetrates deep enough into muscle tissue. Most light is absorbed by the skin, making it difficult to treat deeper tissues. However, near-infrared light (700-900nm wavelengths) has been found to penetrate much more effectively than red light (600-700nm), making it the most commonly used wavelength range in muscle treatment studies. Infrared light beyond 900nm is less effective because it is blocked by water in the cells. Red light is still used, particularly in studies involving smaller animals, where tissue penetration is less of an issue. Wavelengths between 810-830nm are the most popular for treating larger animals like humans or horses.

Higher Power Density Required

Even with ideal wavelengths, much of the light energy is absorbed by the skin and outer layers of tissue. To achieve effective results, a light device needs to provide sufficient power. A power density of less than 50mW/cm² is too weak for penetrating muscle tissue in humans. Studies commonly use devices with power densities of 200mW/cm² or more, and doses of 100J/cm² or higher are recommended to ensure enough energy reaches deeper muscles.

Timing: Before or After Exercise?

Once you have a device with the right wavelengths and power, timing becomes crucial. Current studies show that light therapy is most effective when applied before exercise. This pre-exercise application seems to enhance performance (strength, speed, endurance) and aids recovery. It may also reduce the risk of injury. While post-exercise light therapy is still beneficial for recovery, applying it before exercise has shown superior results. Some suggest using light both before and after exercise may be the optimal approach, though this has yet to be thoroughly tested.

Choosing the Right Device

Studies on muscle light therapy consistently use either LED or laser devices, both of which are energy-efficient, heat-free, and able to provide specific wavelengths. These devices are necessary because muscle tissue is deep within the body, and high doses of light must be applied to the skin for it to reach the muscles. Using less specific lighting technology, such as heat lamps or infrared bulbs, would require extreme amounts of energy, leading to severe skin overexposure and burns.

Summary

Light therapy has been studied for muscles in various ways, including for exercise recovery, injury recovery, strength, endurance, hypertrophy, and pain reduction.

Red and near-infrared light (600-900nm) may help muscle and muscle stem cells by boosting energy production, reducing inflammation, and speeding up healing.

Near-infrared light (740-830nm) penetrates tissue more effectively than other wavelengths.

Light therapy for muscles requires high power densities (200mW/cm² or more) to penetrate deep muscle tissue.

LEDs and lasers are the only viable devices for muscle light therapy; heat lamps and other broad-spectrum lights are not effective.

Current research suggests that using light therapy before exercise maximizes its benefits for performance and recovery.