It was the end of a long, rather blah workday in early March, most likely a Wednesday. I was not excited about attending an evening seminar at the University of Vermont Department of Physical Therapy devoted to the topic of photobiomodulation, a term which describes the ability of light to affect living tissue (Photosynthesis in plants is an example of photobiomodulation). Three weeks before, it had sounded like something interesting and fun to do, and there also was the possibility I might make some new PT friends. Three weeks later, I was tired and trying to come up with excuses to bail out last minute. I could not come up with a good reason to not go, so I went. It turned out that I was absolutely meant to be at that seminar.

The seminar consisted of a presentation by a doctor and a sales representative, both of whom are affiliated with Chattanooga Rehabilitation, on the company’s new class 4 high-powered therapeutic lasers. [Author’s note: When I realized that a sales rep, whose name is Ryan, was part of the presentation, I almost packed up my things and left because I figured they just wanted to sell me something. But there was pizza coming, and I was starving. Now Ryan and I are friends and professional colleagues, and he has been an incredibly patient, knowledgeable and invaluable resource and help to me]. Figuring this was just the usual attempt by a rehab company to sell something, I instantly composed a list of questions in my head about the efficacy of the laser in different clinical cases, the reliability and validity of studies supporting therapeutic laser for musculoskeletal and neurological conditions, and points that I felt were contradictory to the use of laser for certain conditions, such as treating an infected wound (turns out the points weren’t contradictory at all). The presenters calmly and politely provided acceptable answers to all my questions. I’m sure I drove them nuts.

All sounded great, but of course a gang of hardworking, frugal and skeptical PTs needed to see it in action. Fortunately, when you get a gang of PTs together, usually at least one or two people in the group are dealing with some sort of work-related injury (sometimes the entire group is injured), so there were plenty of volunteers for the laser demo. The doctor and sales rep, to their credit, were very clinically objective. They not only obtained a pain rating from each volunteer, but also a clinical measurement, which could be an actual measurement of range of motion at a joint, a measurement of fluid in a joint, or an ability to perform a functional task, such as stand on one foot, or squat as low to the floor as possible. After a short laser treatment, the pain level and objective measurement of every volunteer improved. Some of the volunteers were even a little freaked out by the fact that one treatment made a measurable difference.

So naturally I had to try it, and as luck would have it, I’ve been dealing with chronic tendinitis in my left wrist for probably eight years, work-related and exacerbated by mountain biking. It comes and goes, I had accepted it and figured that one day it would probably end my clinical career. I had fortuitously just returned from a mountain biking trip, so I had a big swollen lump at the base of my thumb that was perfect for the demonstration. The laser treatment lasted four or five minutes and felt like a spa treatment, warm and healing. It was not as sore as usual right after the treatment, but I had no objective improvement. I figured it would work for everyone except me since the tendinitis had persisted for so long, but I couldn’t discount the results of laser treatment on everyone else’s injuries. I left the seminar very interested, but not sure I would be willing or able to invest in the very expensive technology.

As I thought about the class 4 laser over the next few days, an interesting thing happened. The swollen lump above my thumb began to shrink and heal. One week after treatment it was gone. It has not returned, despite doubling my clinical load this summer. I occasionally feel a trace of soreness in the area that used to be swollen, after mountain biking or after a long workday, a transient 1 out of 10 on the pain scale. I called Ryan and scheduled a laser demo day at Points North PT.

The demo day had a party vibe and was a blast. Eleven clients and my husband, all with a condition for which laser treatment could be indicated. We ran the demo in a similar fashion to the UVM seminar, collecting subjective pain scale rating and objective measurements before and after the laser treatments. Everyone exhibited some subjective and/or objective improvement after one treatment—except my husband, naturally, which I figured was intentional so that I wouldn’t spend money on the laser. Interestingly, his issue that was treated with the laser—chronic leg swelling after a persistent skin infection—gradually disappeared within a month of the laser treatment. Whether it was the natural course of healing or that the laser catalyzed resolution of inflammation in his leg, I honestly cannot say.
So the short ending to a long story is that I bought the top-of-the-line laser, the Lightforce XLi class 4 40-Watt laser. I received extensive in-person and online training and now hold two certifications in laser treatment for musculoskeletal conditions. It’s been up and running since May 2023.

I agree that it all sounds too good to be true. It sounds like magic, and also like nonsense. Here’s the science behind laser photobiomodulation: The wavelengths of light in red and near-infrared light, which are the wavelengths of light used in the class 4 laser, act on structures in our cells to stimulate healing. What happens first is that our tissues absorb the light. Next, the light wavelength stimulates our mitochondria, organelles (structures in our cells) which are involved with energy production by acting on an enzyme in the mitochondrial membrane known as cytochrome C oxidase. As part of the cellular respiration, this enzyme catalyzes the conversion of stored energy to active energy (ADP to ATP as part of the Krebs cycle, for the molecular biology/biochemistry/AP bio people reading this). By stimulating this natural process of cellular respiration, the by-product of which is an active energy form then used by the cells, the laser light actually improves the health of the cells via improved oxygenation and more energy. Many benefits come from healthier cells in an injured area, including but not limited to faster resolution of inflammation, improved circulation, improved nerve firing, faster deposition of new tissue, improved immune response, and improved muscle performance.

Photobiomodulation itself is not a new concept. Lasers have been used in physical therapy for quite some time, under the former name of “cold laser,” now know as class 3a and 3b laser. These also work well. The difference between the class 3 lasers and the class 4 lasers lies in the amount of power used. A class 3B laser delivers up to 500 mW of continuous treatment, or up 10 W of pulsed treatment, the cumulative pulses of which combine to deliver approximately 1 W of treatment.

Why does power matter? Higher power reaches greater tissue depths, which gives a high-powered laser the ability to be more effective when treating deeper structures and conditions, or larger people. It also reduces treatment time. For example, a 5-minute treatment of a small area using a low power setting on the high-powered laser, for example 10 Watts, will take 50 minutes with a class 3 laser’s maximum power of 1 Watt. The higher power laser simply can accomplish more in a shorter amount of time.

Red light treatment has become trendy. We now have the ability to purchase red light lamps, red light heating pads, and other red light gadgets on Amazon and other websites and use them for injury, and also indiscriminately for health. Something to know is that over-the-counter red light gadgets are made for usage by the general population and contain extremely low power. To obtain the same tissue effects on an injury that would be provided by a 10-minute treatment of a 1-Watt class 3b laser, one would have to use the red light gadget for 8 to 12 hours, depending on the quality of the device.
The past three months have been a fascinating experience, during which I have been learning how to best use this amazing new technology to help people. What I have found is that the class 4 laser is not magic. It does not work for everything and should not be used on everyone. It does not help people with generalized or nonspecific pain. Like all of physical therapy, and medical treatment in general, it works extremely well, and efficiently, when we can identify and target the specific injured tissue. So far, I am having great results incorporating the laser into treatment of conditions including but not limited to muscle and ligament strains, bursitis, soft tissue contusions/trauma, tendinitis/tendon injuries, nerve root inflammation, scar tissue, and disc bulges.

Kathleen Doehla, PT DPT