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Discover the science behind photobiomodulation therapy (PBMT) for dogs’ athletic performance enhancement. Dr. Chris Zink explains!
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You’ve likely heard of the healing effects of laser therapy. There is abundant, peer-reviewed scientific evidence that light can penetrate the skin and cell membranes and enter mitochondria (the energy producing factories of the cell). There, the light energy is converted into adenosine tri-phosphate (ATP), the form of energy that the cell uses for healing. This is a photochemical effect comparable to photosynthesis in plants whereby light is absorbed by a leaf and undergoes a chemical change to provide energy for the plant.
We shouldn’t really be surprised that light has power. We know, for example, that sunlight can kill bacteria. Although laser technology was invented in the early 1960s, recently, the field has exploded with studies demonstrating the healing effects of light therapy, now officially referred to as photobiomodulation therapy (PBMT). Hundreds of peer-reviewed studies show that PBMT can promote tissue regeneration, reduce the pain of inflammatory conditions such as arthritis, and relieve pain in soft tissues such as muscles, tendons, and ligaments.
Just in the last few years, studies have revealed that PBMT can improve hard-to-treat neurological and psychological conditions such as stroke, traumatic brain injury, Parkinson’s disease, and depression. So, let’s check out how that works.
No one hates physics more than I do, but actually, it is pretty interesting (and simple) when we are talking about how PBMT works. So here are a few FAQs to explain that:
Only light in the infrared or near infrared wavelengths (600 to 1064 nm) can be converted by the cell into energy. These wavelengths of light can be produced by lasers or LEDs. The main difference between the two is that lasers produce more potons, and they are all aimed in one direction, whereas LEDs produce fewer photons that are scattered multidirectionally so that it is hard to determine exactly how much light therapy is actually reaching the target tissue.
In general, the longer the wavelength, the deeper into the tissue the light penetrates.
When dosing with light, we use a unit of energy called the joule (J). One watt (W), or 1000 milliwatts (mW) of power, produces one joule per second. So, a typical laser with a power of 500 mW will produce one joule every two seconds. On the other hand, one LED light in a string of holiday lights has a power of approximately 70 mW, so it will take about 14 seconds for one of those lights to produce one joule of energy. When applying light therapy to a tissue, we describe dose exposure in J/cm2. Doses usually range from 2 to 10 J/cm2.
The best scientific evidence consists of systematic reviews of randomized clinical trials. It just so happens that there is a systematic review of randomized clinical trials examining the effects of PBMT on human sports performance.
That study reviewed 46 randomized, placebo-controlled clinical trials that included 1,045 participants. It concluded that PBMT can increase muscle mass gained after training, and decrease inflammation and oxidative stress in muscles. They postulate that these effects are related to the fact that PBMT is known to increase ATP, the biological source of energy needed for muscle work. The review quotes many different studies that show improved performance of various muscle groups in humans. As an example, lets discuss one of the most practical, real-world studies—one that examined the effects of PBMT on the performance of high-level rugby players.
In that study, 12 male, world-class rugby players were treated with PBMT (using both lasers and LEDs) or placebo, then run seven times through a timed sprint test that included turns, much like a dog Agility course. PBMT significantly improved the average time for all sprints as well as measured and perceived fatigue, and blood lactate levels (a by-product of muscle energy metabolism). Pretty cool!
The question of dosing is especially important because many people think, “If low doses are beneficial, higher doses must be even more so!” Unfortunately, that is not the case. Numerous studies have shown that low doses of PBMT are beneficial, but higher doses can have no effect or might, in fact, be harmful. This biological process is called hormesis (Figure 1), just so you can impress your friends with your scientific vocabulary. In any case, this little detail makes knowing the appropriate dose of PBMT very important!
Another important question to be answered is: how can we apply these bare-skinned human studies to our hairy dogs? How do we know how much of the light source will penetrate a dog’s coat to get to the skin? A laser treatment can be applied by hand, parting the coat and ensuring that the skin is exposed to the light, but ideally, the dog should be shaved to get the full effect of the light that is emitted. This is even more true for LED products, which usually consist of arrays of small LEDs in a stiff or flexible casement. The Internet abounds with LED products that claim to treat a variety of problems in dogs (based loosely on the effects of PBMT in humans), but not a single one takes into account LED penetration through the fur. In fact, there are even concerns with penetration of laser light through fur. With so many different densities of fur in different breeds, this is an important issue. Perhaps we should only use LED arrays on Chinese Cresteds or Xoloitzcuintlis!
An additional confounding factor is the fact that the darker the skin, the less the light penetrates to the tissues below. This factor also has only been studied in humans, not dogs. So, if you have a hairy, dark-skinned dog, how much of the light is going to penetrate to the muscles where you want it to have its effect? We don’t know, but some have suggested less than 5%. So, at this point, at least for dogs, PBMT to improve performance is not quite ready for primetime.
Despite all of these cautions, however, the evidence is quite convincing that, if you can get light of the right wavelength and power to penetrate to the muscle, it has the potential to significantly improve your dog’s athletic performance. The data in humans are so convincing that some studies suggest that PBMT be placed on the World Anti-Doping Agency’s list of prohibited substances, although how they will know whether a person has been treated has yet to come to light! 
A dog receiving laser therapy, with the therapist using the correct precautions against errant light for both herself and the dog.
Can I Start Using Laser Therapy to Improve My Dog’s Performance?Despite growing evidence of the benefits of PBMT on sports performance, there are many questions to be answered before you can magically use laser or LED to turn your favorite furry athlete into a super-canine star.
This is one place where the expression “let the buyer beware” has never been more true. Many companies sell lasers that are completely ineffective for treating your dog’s injuries. After all, you can use a laser pointer when giving a presentation or to play with your cat, but it certainly wouldn’t be effective in healing.
Expect to pay several thousand dollars for a Class IIIB laser with a minimum of 500 mW power. The less power the laser has, the longer it will take to treat your dog. Before purchasing, get the advice of a veterinarian certified in rehabilitation therapy.
“If low doses are beneficial, higher doses must be even more so!” Unfortunately, that is not the case.
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