Understanding PBM or laser light therapy dosing is a bit like understanding cooking — heat intensity and time are crucial…
Photobiomodulation (PBM THERAPY), previously known as low-level laser therapy (LLLT) or “cold laser,” is a popular tool for a wide range of musculoskeletal pathologies (back pain, neck pain, muscle, tendon and joint pain). Laser light therapy is cleared in the United States by the U.S. Food and Drug Administration for the “temporary relief of minor muscle and joint pain and stiffness, minor arthritis pain, or muscle spasm; the temporary increase in local circulation and the temporary relaxation of muscle.”
Laser light therapy: evidence base, effectiveness and overdosing
At least 200 randomized placebo-controlled clinical trials (RCTs) have been published on the effects of PBM on musculoskeletal pain, with a further 500 RCTs published on a variety of pathologies including neuropathies, non-healing wounds, headaches, dental pain, cancer treatment side effects, and even the brain. More than 90 systematic reviews with meta-analysis have pooled the data for a wide range of clinical applications providing summaries mostly in favor of PBM as a safe and effective medical intervention.
In a systematic review and meta-analysis of laser therapy on tendinopathies (Tumilty et al. 2009), 13 out of 25 published randomized controlled clinical trials (52%) of laser tendinopathy studies failed to produce a positive result. The reason identified was “treatment overdose.” Tumilty subsequently wrote a paper titled “The Dose That Works: Low Level Laser Treatment of Tendinopathy.” It is a free-to-download paper and worth searching for online.
Have we been doing it wrong?
Understanding laser light therapy dose is a bit like understanding cooking. The two things you have to get right when cooking are the heat intensity of your oven and the cooking time. It is the same for PBM — the two things you have to get right are the light intensity and treatment time.
There is a myth on the internet that you can increase PBM laser power intensity by a factor of 10, treat for 1/10th of the time and expect to achieve the same result. It does not work in cooking and it does not work in PBM. Tumilty and many others have found limits to the total dose and the rate at which it is delivered. Light intensity in PBM is called the “irradiance” and is expressed in W/cm2; this is called the “dose rate.”
The dose that works
In summary, Tumilty’s paper found that the 12 positive studies effectively used the dosage window in the World Association for Laser Therapy (WALT) guidelines. Below is a sample from a table of data showing Jan Bjordal’s dose-rate information as reported in Tumilty’s free-to-download paper.
Assuming that you already own a laser, let’s say you want to treat a superficial pathology (less than 1 cm below the skin surface, such as an Achilles tendinopathy), and you want to stay safely inside Bjordal’s dose-rate window. I suggest you deliver 50 mW/cm2 to each tender area for 1 minute (which equals 3J/cm2) 2-3 times a week for at least three weeks (then you can reduce the number of weekly treatments until the patient is discharged). Whether you own a Class 4 laser or a Class 3B laser, the manufacturer should be able to advise you on how to achieve 50 mW/cm2.
Treating more than the symptoms and increasing your business
There is more to laser light therapy than just treating the symptoms. We teach treatment of myofascial trigger points, lymphatics, nerves for analgesia and even bone marrow for stem cell release.
PBM can inhibit as well as stimulate, and the techniques and settings for consistently achieving these results have not always been clear. Should you use laser or LED, red or infrared wavelengths, use a strong or a low-power laser, use pulses or continuous, treat twice a day or twice a month?
Laser light therapy dose is critical to your patient outcomes and therefore critical to repeat business and referrals. Just like manual therapies and pharmaceuticals, getting the dose right will improve patient success and create loyal fans for your high-tech therapy investment.
James D. Carroll is founder and CEO of THOR Photomedicine and has more than 30 years of photobiomodulation experience. He has coauthored 22 PBM papers and contributed chapters to five PBM books. Learn more at thorlaser.com.