Participation in sports promotes a physically active lifestyle, but carries an inherent risk associated with the nature of the sport and the physical demands placed on competitors. Athletes from all levels of participation, from student, collegiate and professional to recreational, often suffer from injuries, and rapid recovery is desired for a speedy return to competition. There is a growing trend for both professional and recreational athletes to utilize chiropractic care in both official and unofficial capacities to restore function. Laser therapy has been shown to be beneficial when managing sports injuries and continues to grow in popularity.
Laser therapy was first introduced in the early 1980s as a means to resolve musculoskeletal pain. Since the first clinical trial was published investigating the effects of low-level laser therapy (LLLT) on rheumatoid arthritis,1 the positive effects of LLLT have been identified in other pathologies as well, including osteoarthritis,2 tendinopathies,3-4 wounds,5-6 back pain7 and neck pain.8-9
Low-level laser therapy has only been used in the United States since 2002, primarily in clinic settings. However, novel research continues to uncover other benefits and applications that chiropractic sports specialists in particular will find of interest. Going beyond accelerating injury rehab, LLLT has been shown to be particularly useful in the world of recreational and competitive sports by optimizing performance and training. This new research shows that laser may protect muscles from physical and chemical damage, improving athletes' field performance and recovery time following vigorous training and conditioning.
Mechanism of Action
While Albert Einstein first proposed the term LASER (Light Amplification by Stimulated Emission of Radiation) in 1905, the first laser was not developed until the 1960s, giving rise to a new form of therapy called low-level laser therapy or LLLT. As defined by the North American Association for Light Therapy (NAALT), LLLT is any modality that utilizes photons of light (usually red and/or infrared) for tissue healing and pain reduction.10
It has been hypothesized that photonic energy absorbed by the cellular mitochondria fuels many physiological responses, called photobiostimulation, resulting in the restoration of normal cell morphology and function. Photostimulation is the process whereby a chain of chemical reactions is triggered by exposure to light.
LLLT is typically applied trancutaneously through the skin with a low-power laser or light-emitting diode (LED). There are several unique properties of laser (monochromaticity, coherence and low divergence) that allow photons to reach deep tissues like muscles, tendons and others. The light is typically11 of narrow spectral width in the red or near-infrared (NIR) spectrum (600 nm - 1,000 nm), with power output in the range of 1 mW – 500 mW, a power density (irradiance) between 1 mW to 5 W/cm2. As a point of interest, the vast amount of all laser therapy research has been performed with low-level lasers with these parameters.
Uses Beyond Rehabilitation: Athletic Performance and Recovery
Despite the documented health benefits of increased physical activity (e.g., weight management, improved self-esteem, and increased strength, endurance, and flexibility),12 those who participate in athletics are at risk for sports-related injuries.13-14 Athletes from all levels of participation – student, collegiate, professional and recreational – will suffer from injuries or worse, overtraining.
Athletes engage in training programs designed to improve endurance, speed, strength, explosive power, mental focus, agility and core strength. Exercise is a stressor that produces catabolic effects on the body, consumes contractile proteins within muscles for energy and strains connective tissue. The body's reaction to this stimulus is to adapt and replete tissues at a higher level than that existing before exercising. The results of regular training exercise are increased muscular strength, endurance, bone density, and connective-tissue toughness.
Many injuries are the result of overtraining or fatigue. Some are more severe than others. It is theorized that fatigue can be a contributing factor in sports injuries because it is more difficult for the body to protect itself when fatigued.15
The genesis of many injures that occur later in an athlete's career are due to improper training early in their career. Adequate time and rest is necessary for recovery; however, athletes always desire a more rapid recovery to continue training and conditioning. Laser therapy is showing promising results in improving performance and demonstrating that recovery requires more than just rest and water intake to resolve the catabolic effects of training.
Laser-Powered Training
Skeletal muscle fatigue is a novel area of research in LLLT. In the past few years, a Brazilian research group has performed a series of animal experiments and clinical trials16-27 that suggest very positive results from LLLT in terms of improving exercise performance and exercise recovery. The following table is a summary of the main results in the clinical trials. It is important to highlight that all studies were published in peer-reviewed scientific journals. [See reference list at end of article for complete citations.]
Table 1: Summary of clinical trials in LLLT and exercise performance and recovery performed by our research group.
| Authors | Source of light | Wavelength (nm) | Energy density per diode (J/cm2) | Energy per site (J) | Power density per diode (W/cm2) | Treatment time per point or site (sec) |
| Leal Junior, et al. 2008 | Laser | 655 | 500 | 5 | 5 | 100 |
| Leal Junior, et al. 2009a | Laser | 830 | 1,785 | 5 | 35.7 | 50 |
| Leal Junior, et al .2009b | Laser | 830 | 1,428 or 1,071 | 4 or 3 | 35.7 | 40 or 30 |
| Leal Junior, et al. 2009c | Laser / LED | 810 / 660 and 850 | 164.85 / 1.5and 4.5 | 6 / 41.7 | 5.50 / 0.05 and 0.15 | 30 / 30 |
| Leal Junior, et al. 2009d | LED | 660 and 850 | 1.5 and 4.5 | 41.7 | 0.05 and 0.15 | 30 |
| Leal Junior, et al. 2010b | Laser | 810 | 164.85 | 30 | 5.5 | 30 |
| Leal Junior et al. 2011 | LED | 660 and 850 | 1.5 and 4.5 | 41.7 | 0.05 and 0.15 | 30 |
| Almeida, et al. 2012 | Laser | 660 or 830 | 1,785 | 5 | 17.85 | 100 |
| De Marchi, et al. 2012 | Laser | 810 | 164.85 | 30 | 5.5 | 30 |
| Miranda et al. 2013 | LED | 660 and 850 | 1.5 and 4.5 | 41.7 | 0.05 and 0.15 | 30 |
| Authors | Power output per diode (mW) | Total energy delivered (J) | Number of treated points or sites | Muscle treated | When LLLT was applied? | Results |
| Leal Junior, et al. 2008 | 50 | 20 | 4 | Biceps brachii | Before exercise | LLLT increased number of repetitions compared to placebo |
| Leal Junior, et al. 2009a | 100 | 20 | 4 | Biceps brachii | Before exercise | LLLT increased number of repetitions compared to placebo |
| Leal Junior, et al .2009b | 100 | 40 or 30 | 5 each leg = 10 in total | Rectus femoris | Before exercise | LLLT decreased CK activity and lactate levels after exercise comparedto placebo |
| Leal Junior, et al. 2009c | 200 / 10 and 30 | 12 / 83.4 | 2 sites per limb with a single diode laser or a multidiode LED cluster(69 LEDs -34 red and 35infrared) | Rectus femoris | Before exercise | LLLT significantly decreased CK activity after exercise |
| Leal Junior, et al. 2009d | 10 and 30 | 41.7 | 1 site with a LED cluster (69 LEDs – 34 red and 35 infrared) | Biceps brachii | Before exercise | LLLT increased number of repetitions and time until exhaustion, anddecreased CK, CRP, and lactate levels compared to placebo |
| Leal Junior, et al. 2010b | 200 | 60 | 2 sites with a multidiode cluster with 5 spots (6 J each spot) | Biceps brachii | Before exercise | LLLT increased number of repetitions and time until exhaustion, anddecreased CK, CRP, and lactate levels compared to placebo |
| Leal Junior et al. 2011 | 10 and 30 | 417 (208.5 per lower limb) | 5 sites each lower limb with a LED cluster (69 LEDs -34 red and 35 infrared) | Quadriceps (2 sites), Hamstrings (2 sites), Gastrocnemius (1 sites) | After exercise | LLLT significantly decreased CK activity and lactate levels afterexercise compared to cold water immersion therapy and placebo |
| Almeida, et al. 2012 | 50 | 20 | 4 | Biceps brachii | Before exercise | LLLT increased average strength and peak strength compared to placebo |
| De Marchi, et al. 2012 | 200 | 720 (360 per lower limb) | 12 sites each lower limb with a multidiode cluster with 5 spots (6 Jeach spot) | Quadriceps (6 sites), Hamstrings (4 sites), Gastrocnemius (2 sites) | Before exercise | LLLT increased VO2 max and time until exhaustion, decreasedCK and LDH activity, decreased oxidative stress and increased antioxidantactivity compared to placebo |
| Miranda et al. 2013 | 10 and 30 | 125.1 | 3 | Quadriceps | Before exercise | LLLT increased time until exhaustion compared to placebo |
Results from 10 clinical trials already published suggest that LLLT improves exercise performance and recovery. When LLLT is applied before exercise, it appears to help protect muscles against exercise-induced damage and inflammation. This means our results can be translated and used in several situations in which improvement in muscle performance is required.
Currently, we are working to establish the optimal dose and parameters of LLLT for the improvement of exercise performance and enhancement of exercise recovery. There may be additional benefits of combining LLLT with other modalities, such as cryotherapy, for instance. Our preliminary results suggest that LLLT has a dose-response pattern, and different doses must be applied for short-term or long-term improvement of exercise performance and enhancement of exercise recovery. Additionally, our data suggest that cryotherapy can decrease efficacy of LLLT regarding biochemical markers related to exercise recovery.
Laser therapy has been assisting athletes to recover from injuries for years, accelerating the healing process. Now, LLLT may have the added benefit of improving an athlete's sports performance by allowing athletes to prepare, perform and recover from the catabolic stressors of intense training and competition.
References
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