Apr 28, 2020Why are more sports healthcare professionals seeing the light?
The use of light therapy for therapeutic purposes has been around for over 50 years. In 1967, Mester, et al. (1) reported on the effects of laser biostimulation for the treatment of musculoskeletal conditions. Since then, the use of therapeutic light has rapidly gained acceptance in both the medical and rehabilitation communities.
LASER, which stands for “light amplification by stimulated emission of radiation,” is a type of device that can now be found in a variety of settings, with most professional sports teams and many collegiate division I programs utilizing this modality as part of their treatment protocols. As technology has progressed, these devices have become more sophisticated, as well as more affordable.
The vast majority of laser therapy being utilized in the therapeutic setting is referred to as Low-Level Laser Therapy, or LLLT devices, which are also referred to as cold lasers. These are low-powered devices that primarily create non-thermal effects, and are relatively safe to use. Other forms of light therapy include high powered lasers and light-emitting diode (LED) devices.
The science behind these devices is based upon the concept of photobiomodulation, which suggests that the penetration of light deep into tissues can initiate a multitude of both physical and chemical changes. This is primarily dependent upon the type of light form used, as well as the wavelength and dosage. Light with a wavelength in the red to near-infrared region (600nm- 905nm) is most commonly utilized in these devices (2).
When therapeutic light is sent into the tissues, some of it is absorbed into the epidermis, however, photons can reach deeper structures as well. One of the cellular targets of this type of therapy is the mitochondria of the cell, in particular Cytochrome c oxidase (COX). COX is a terminal enzyme of the electron transport chain and plays a vital role in the bioenergetics of the cell (3). It is believed that an increase in electron transport activity can lead to an increase in the production of ATP as well, which is vital to cell energetics.
Another biochemical target of laser therapy is the production of Nitrous Oxide (NO). It has been proposed that laser irradiation could lead to the dissociation of NO from the COX enzyme, which has the potential benefit of preventing the inhibition of COX, leading to an increase in cellular respiration as well (Farivar-18). This is thought to lead to a light-mediated vasodilation in the tissues (4). It is also thought that the inhibition of NO can lead to a decrease in cell death (induced by NO) as well (5).
Studies by Karu (6) suggest that LLLT produces a shift in the cell toward greater oxidation by an increase in the generation of reactive oxygen species (ROS). This is associated with a change in the activity of cellular signaling pathways as well as gene expression within the cell. Furthermore, this activity can be associated with an increase in protein synthesis, nucleic acid synthesis, and cell cycle progression (7).
So what parameters should a clinician consider, when deciding what type of light therapy to use. With regard to low-level laser therapy, most of the devices work by exhibiting a biphasic dose-response curve, otherwise referred to as the Arndt-Schultz principle (8,9). This principle suggests that lower doses of light are possibly more effective than much higher doses.
As alluded to earlier, most of these LLLT devices generate light in the red visible, or near-infrared bands of the electromagnetic spectrum, with wavelengths in the range of 600-1000nm. These devices are identified as class 3A or 3B lasers and are not thought to stimulate any appreciable thermal effects. These devices are often designed as a single emitter, or in a “cluster”, which is a less common configuration. The output may be either continuous or pulsed. The longer wavelengths (>1300nm) appear to be rapidly absorbed by water, thereby having less penetration, hence why most units sold work within the lower wavelengths previously noted.
The parameters of how to use these devices are dependent upon the output power (watts or mW), irradiation area (cm2), and time (seconds). The energy delivered is measured in Joules (J). The energy density is calculated by the total amount of energy divided by the irradiation area (J/cm2). Units that have a higher power output, and larger irradiation area, often require shorter treatment times. This is one of the arguments put forth for the use of high powered lasers, which allow clinicians to treat tissues utilizing much shorter treatment times. However, with increasing power, comes the risk of potential tissue damage if overtreatment occurs. The use of LLLT devices is not thought to present this same risk, hence why they are more commonly found in most clinical settings. Treatment times often fit into the range of 30 to 60 seconds per treatment point for most devices, and the total treatment time depends upon the number of points being treated in a session. Larger tissue areas, such as the lower back, often require more treatment points than a smaller structure like a toe. This is why new devices like LED pads are becoming increasingly popular, as they allow for larger areas to be treated, often unattended, allowing for greater clinical efficiency. Another advantage to LED devices is a decreased risk to ocular structures in the eye, which has long been one of the chief concerns with using laser devices in a clinical setting without wearing appropriate eyewear for everyone in the room where the treatment is occurring.
It has long been acknowledged in the literature that therapeutic lasers can have a beneficial effect in the treatment of dermatologic conditions, as well as to stimulate intra-oral healing. The use of therapeutic light therapies for musculoskeletal conditions is less clear, although over the last few decades research has begun to demonstrate a clearer appreciation for its role in the treatment of tissue pain, and stimulate a more rapid healing response in muscle and joint conditions, amongst other clinical uses. Recently, a systematic review and meta-analysis of the effects of LLLT on pain and disability in knee osteoarthritis, published in the British Medical Journal, found that it significantly reduced pain, as compared to placebo, as well as a notable reduction in disability (10). Takenori (11) and colleagues, in a randomized, double-blind placebo clinical trial, found that LLLT performed on a cohort of collegiate athletes led to an almost immediate 30% reduction in pain in almost 75% of the participants. A paper by Vinck (12) suggests that one potential role that laser therapy may play in reducing pain may be through its ability to modulate nerve conduction and reducing action potentials. Other studies have come to similar conclusions.
In a pilot study by Foley and colleagues (13), which examined the role of LED phototherapy in facilitating return to play in injured university athletes, a total of 395 injuries, including sprains, strains, tendinopathies, and contusions were treated over 1,669 sessions. It was found that the use of an 830nm LED device led to a quicker recovery and return to play. Although a control group was not utilized in the study, it nonetheless suggests therapeutic light may play an important role in facilitating the healing process (13).
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However, one of the most exciting developments in the literature examines the role laser therapy may play in the role of enhancing tissue recovery and improving performance. A randomized controlled trial by Tomazoni and colleagues (14) examined the role of LLLT, applied prior to an intense running session in high-level soccer players, on markers of muscle damage, inflammation, and oxidative stress in the tissues. It was found that utilizing laser therapy prior to running reduced muscle damage, led to reductions in the levels of creatine kinase and lactate dehydrogenase post-exercise, as well as interleukin-6, in addition to other biomarkers. Furthermore, the athletes treated with the laser also showed improvements in VO2 max, as well as both aerobic and anaerobic thresholds during the exercise session.
In a similar study published in the Journal of Strength and Conditioning Research (15), a randomized, double-blind, placebo-controlled study also found that pre-exercise photobiomodulation therapy not only improved average time of sprints performed and fatigue index in an anaerobic testing protocol but also decreased the percentage of change in blood lactate levels post-exercise.
It is becoming increasingly clear that photobiomodulation therapies, including low-level laser therapy, high-powered laser, and LED cluster devices, are showing efficacy in both the treatment of injuries and as a method to enhance athletic performance and recovery. It would be wise for clinicians and performance coaches alike to further explore how to incorporate these devices into their therapeutic regimens, as a way to improve their clinical outcomes and performance enhancement programs.
- Mester E, Ludany G, Sellyei M, et al. Studies on the inhibiting and activating effects of laser beams. Langenbecks Arch Chir. 1968; 322:1022-1027.
- Cotler HB, Chow RT, Hamblin MR, Carroll J. The use of low level laser therapy for musculoskeletal pain. MOJ Orthop Rheumatol. 2015; 2(5).
- Srinivasan S, Avadhani NG. Cytochrome c oxidase dysfunction in oxidative stress. Free Radic Biol Med. 2012; 53(6):1252-63.
- Ehrreich SJ, Furchgott RF. Relaxation of mammalian smooth muscles by visible and ultraviolet radiation. Nature. 1968; 218(5142):682-94.
- Hamblin MR. Mechanisms of low level light therapy. Proc of SPIE. 2009; 6140: 614001-1.
- Karu T. Primary and secondary mechanisms of action of visible to near-IR radiation on cells. J Photochem Photobiol. 1999; 49(1):1-17.
- Liu H, Colavitti R, Rovira II, Finkel T. Redox-dependent transcriptional regulation. Circ Res. 2005; 97(10):967-974.
- Woodruff LD, Bounkeo JM, Brannon WM, et al. The efficacy of laser therapy in wound repair: a meta-analysis of the literature. Photomed Laser Surg. 2004; 22(3):241-247.
- Huang YY, Chen AC, Carroll JD, Hamblin MR. Biphasic dose response in low level light therapy. Dose Response. 2009; 7(4):358-383.
- Stausholm MB, Naterstad IF, Joensen J, et al. Efficacy of low-level laser therapy on pain and disability in knee osteoarthritis: systematic review and meta-analysis of randomized placebo-controlled trials. Brit Med J. 2019; Open access 9:e031142.
- Takenori A, Ikuhiro M, Shogo U, Hiroe K, et al. Immediate pain relief effect of low level laser therapy for sports injuries: randomized, double-blind placebo controlled trial. J Sci Med Sport. 2016, Dec; 19(12):980-983.
- Vinck E, et al. Evidence of changes in sural nerve conduction mediated by light emitting diode irradiation. Lasers Med Sci. 2005; 20(1):35-40.
- Foley J, Vasily DB, Bradle J, Rudio C, Calderhead, RG. 830nm light-emitting diode (LED) phototherapy significantly reduced return-to-play in injured university athletes: a pilot study. Laser Therapy. 2016; 25(1):35-42.
- Tomazoni SS, Monteiro-Machado C, DeMarchi T, et al. Infrared low-level laser therapy (photobiomodulation therapy) before intense progressive running test of high-level soccer players: effects on functional, muscle damage, inflammatory, and oxidative stress markers- a randomized controlled trial. Oxidative Med and Cell Longevity. 2019; Hindawi-Article ID 6239058.
Pinto HD, Vanin AA, Miranda EF, Tomazoni SS, et al. Photobiomodulation therapy improves performance and accelerates recovery of high-level rugby players in field test: a randomized, crossover, double-blind, placebo controlled clinical study. J Strength Cond Res. 2016; 30(12):3329-3338.