Muscle Light Therapy
One of the lesser known parts of the body that light therapy studies have examined is the muscles. Human muscle tissue has highly specialised systems for energy production, needing to be able to provide energy for both long periods of low consumption and short periods of intense consumption. Research in this area has accelerated dramatically in the last couple of years, with dozens of new high quality studies every month.
Red and infrared light have been studied intensively for a variety of ailments and conditions, from joint pain to wound healing, possibly because the cellular effects are theorised to work on a foundational energetic level. So if light penetrates down into muscle tissue, can it exert beneficial effects there? In this article we will examine how light interacts with these systems and what benefits it may bring, if any.
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Light might interact with muscle function, but how?
- The light therapy mechanism
- The muscle-energy connection
- Muscle stem cells – growth & repair enhanced by light?
- Inflammation
Light therapy may or may not also help muscles indirectly by:
- Thyroid regulation
- Sleep improvement
- Testosterone boost
The potential benefits to muscle function from light therapy
Hypertrophy
The increase in size of muscles as a result of exercise (known as hypertrophy) has been studied in conjunction with light therapy, with interesting results2,14. In the context of muscle tissue, hypertrophy is part of an adaptive response that helps the tissue to generate more force with less fatigue. The physical appearance of long term gains in muscle size is highly sought after by bodybuilders and anyone trying to improve their shape/physique.Changes in muscle size over an 8 week period of resistance training of leg muscles. Control (no exercise, no light) vs Exercise only vs Exercise+Light.2
There is interesting evidence in some limited studies that using appropriate forms of near-infrared light before weight training potentially improves hypertrophy and muscle size gains compared to doing the same weight training exercises without any light. In the limited studies referenced above, specifically a group of untrained people, weight training with light therapy was associated with a doubling in muscle size gains over a period of 8 weeks, compared to doing the same exercise without any light therapy. This makes light therapy a potentially interesting tool for personal trainers10, or for elite athletes exercising alone11,12,16,18, or even just for regular people especially after a period of being sedentary2, potentially aiding your first few month’s progress, and being an aid in the long term too. Although this specific study was done on untrained individuals, there is reason to believe it will be effective for even well trained athletes10,11,18, maybe adding an edge to exercise results.Strength – get stronger with light therapy?
Briefly mentioned above, light could interact with Myosatellite cells and regular muscle cells by potentially improving energy production. This would in theory give an immediate increase in strength and endurance through the regular muscle cells12,13,14,20, but also a long term increase through the myosatellite cells (relative to exercising without any complimentary light therapy)4.One-rep max after dozens of training sessions, followed by either placebo treatment or 850nm LED treatment, in identical twins14.
The studies looking at this tend to examine peak torque – the maximum force generated by a specific movement – and how this changes over time. Just like with hypertrophy, or to some extent because of hypertrophy, light therapy in conjunction with exercise, in these studies, clearly improved the gains in strength compared to exercise alone2. The gains have been significant across a wide range of studies, so much so that international regulatory authorities for sports are considering whether light therapy should even be permitted10.Reduce DOMS/soreness with light therapy?
Several studies on muscle light therapy now point to the potential reduction, and quicker resolution, of delayed onset muscle soreness4,14 – the uncomfortable, yet sometimes satisfying, feeling you get in muscles the day after a tough workout. DOMS is thought to be caused by microtrauma to muscle fibers and is characterised on a cellular level by a rapid influx of calcium into the cell (amongst other things), which inhibits respiration. The displaced calcium entering the muscle cells can lead to damage and inflammation, hence the painful/sore feeling.Severity of muscle soreness after exercise (DOMS) measured by the visual analogue scale (VAS) with placebo or with 850nm LED light therapy after exercise14
The calcium needs to be transported out of the cell again for recovery to proceed, and the cell needs ATP (energy) to do this. Fortunately the hypothesis explaining light therapy is that it potentially speeds up production of ATP (not to mention helping us to produce CO2 which reduces inflammation), and would thereby perhaps speed up the whole muscle recovery process7,8,9, which would in theory reduce both the severity of DOMS and the length of time until full recovery.Improve injury/strain recovery with light?
Various studies point to the potentially positive effects of appropriately used light on post-injury recovery3,4,7,9. One risk of muscle injuries in general is the formation of fibrosis or scar tissue. Just as we get scars on the skin as a result of damage, we can also get them inside the muscles as the inflammatory response causes a spike in collagen formation. Light therapy may help to prevent that scarring5. When scar tissue forms in muscles, this permanently alters the function and mechanical properties of the muscle, leading to reduction in mobility/strength, long term pain, perhaps ending an athlete’s career or even disability in extreme cases. Resolving the injury as quickly as possible with as little inflammation as possible is crucial. Light therapy could be effective here for several reasons – as mentioned above it seems to be useful in reducing the acute inflammatory response, but also in kick starting and supporting the key processes of the muscle recovery process on a cellular level. Indeed this healing effect found in some studies on light therapy is apparent on not just muscle injuries, but also studied on wounds anywhere on the body, such as the skin but even brain trauma and broken bones.Ideal light for muscle light therapy
- Infrared penetrates more than red
- Higher power density / high dose required
- Before or after exercise?
- What light specifically?
Summary
- Exercise recovery, injury recovery, muscle strength/endurance, hypertrophy, pain reduction and more.
- In theory requires a high power density of light (200mW/cm² or more) to achieve the penetration in bigger muscles.
References
- Low-level laser (light) therapy (LLLT) on muscle tissue: performance, fatigue and repair benefited by the power of light. Cleber Ferraresi et al. 2012
- Effect of low-level laser therapy on muscle adaptation to knee extensor eccentric training. Baroni BM et al. 2015
- The low-level laser therapy on muscle injury recovery: literature review. Daniel Rodrigues dos Santos et al. 2010
- Does Phototherapy Enhance Skeletal Muscle Contractile Function and Postexercise Recovery? A Systematic Review. Paul A Borsa et al. 2013
- Low-level laser therapy (808 nm) contributes to muscle regeneration and prevents fibrosis in rat tibialis anterior muscle after cryolesion. Assis L et al. 2013
- Mitophagy-driven mitochondrial rejuvenation regulates stem cell fate. Vazquez-Martin A et al. 2016
- Red and Infrared Low-Level Laser Therapy Prior to Injury with or without Administration after Injury Modulate Oxidative Stress during the Muscle Repair Process. Ribeiro BG et al. 2016
- Effects of low-level laser therapy on ROS homeostasis and expression of IGF-1 and TGF-β1 in skeletal muscle during the repair process. Luo L et al. 2013
- Effects of low-level laser therapy on skeletal muscle repair: a systematic review. Alves AN et al. 2014
- Photobiomodulation in human muscle tissue: an advantage in sports performance? Ferraresi C et al. 2016
- Muscular pre-conditioning using light-emitting diode therapy (LEDT) for high-intensity exercise: a randomized double-blind placebo-controlled trial with a single elite runner. Ferraresi C et al. 2015
- Photobiomodulation Therapy Improves Performance and Accelerates Recovery of High-Level Rugby Players in Field Test: A Randomized, Crossover, Double-Blind, Placebo-Controlled Clinical Study. Pinto HD et al. 2016
- Light-emitting diode therapy in exercise-trained mice increases muscle performance, cytochrome c oxidase activity, ATP and cell proliferation. Ferraresi C et al. 2016
- Effects of Light-Emitting Diode Therapy on Muscle Hypertrophy, Gene Expression, Performance, Damage, and Delayed-Onset Muscle Soreness: Case-control Study with a Pair of Identical Twins. Ferraresi C et al. 2016
- Effect of phototherapy (low-level laser therapy and light-emitting diode therapy) on exercise performance and markers of exercise recovery: a systematic review with meta-analysis. Leal-Junior EC et al. 2015
- Comparison between cold water immersion therapy (CWIT) and light emitting diode therapy (LEDT) in short-term skeletal muscle recovery after high-intensity exercise in athletes–preliminary results. Leal Junior EC et al. 2011
- Effect of 830 nm low-level laser therapy in exercise-induced skeletal muscle fatigue in humans. Leal Junior EC et al. 2009
- Effect of 830 nm low-level laser therapy applied before high-intensity exercises on skeletal muscle recovery in athletes. Leal Junior EC et al. 2009
- 830 nm light-emitting diode (led) phototherapy significantly reduced return-to-play in injured university athletes: a pilot study. Foley J et al. 2016
- Near-infrared light therapy to attenuate strength loss after strenuous resistance exercise. Larkin-Kaiser KA et al. 2015