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High Intensity Laser - Alarming lack of evidence ?

Dear colleagues

My name is Rok, and i am a sports physiotherapist . In my practice i have been using high intensity laser (K-laser, cube 3) for the last 5 years.

Recently, i have tried to get some better understanding on the basic mechanisms of class 4 (HILT) therapy (which seems to be beneficial in a clinical setting, but purely anecdotal). Even though i am quite skilled in finding adequate scientific literature, i have been really struggling to find good (exact) information on class 4 laser mechanism of action and would really appreciate some help ...

My questions are following:

1.) How that even class 4 laser producers advocate and sell their expensive therapeutic machines based on papaers that have been studied on LLLT ? As the main advantage of HILT (having potential clinical benefits) should have been the ability to generate greater power and deliver much energy to the healing tissue? 2.) Can we make a direct comparison between LLLT and HILT mechanisms of action ? 3.) Can we take seriously some commercial claims that using multiple vavelengths (: 660 nm, 800 nm, 905 nm, 970 nm) are superior in comparison to lesser? This is especially confusing as there is some literature out there ( ), suggesting that different wavelengths may actually have an opposing effect on ROS and even contra productive effect on healing?

I would be really thankful on your feedback, and hopefully we can get a better understanding on some of these topics

Kind regards, Rok

Rok Zagar

1 month ago

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Cliff Eaton
Cliff Eaton

Dear Rok Firstly please accept our apologies for not getting back to you sooner. Unfortunately for the second time now this site has been attacked by hackers. The site therefore has not been active and panel members are still not being notified of new posts. Why hackers wish to attack a site like this beggars belief! Ive just completed a 1.5 hr on -line webinar for Australia and NZ on the subject of HPL I will try to be concise in giving you some answers As a relatively new intervention it is not surprising that as yet we do not have the quantity of evidence we would like. As you rightly point out the claims for biological effects are based on LLLT. Perhaps not surprisingly though as the property of the light is the same. The effects are nicely summarised by Hamblin et al., (2017). Quite a bit of interest in this paper at present, form ICUs, as they mention the use of LLLT to reduce lung inflammation. Ash et al., (2017) demonstrate that longer wavelegths travel deeper into the tissue. That alone though does not mean more therapeutic value. The therapeutic value comes from the amount of Photos that reach the affected area. So it is hypothesised that having a long wavelength with more power should result in deeper therapeutic values. Huang et al., (2011) showed that short wavelengths were mostly absorbed in the epidermis, with a large drop off after this level (50%) but longer wave lengths travelled deeper. So the theory behind adding short and long wavelengths is to allow more photos to be transmitted deeper into the tissue. The analogy I use in my talks is one of a tower of sponges. Each one representing tissue. If a short wavelength was like paint in viscosity it would only penetrate very superficially if poured onto the sponges. This would be the case however much paint we poured on. If long wave lengths could be likened to water, a small amount (low power) would penetrate the top sponge. However if more water (more power) was poured onto the sponges far more would get wet. The suggestion being that once superficial cells (top sponge) has fully absorbed the photon energy, then more photons applied will pass these cells and influence cells (sponges) below The systematic reviews that I have read (a couple cited below) comparing outcomes, for the same condition, using LLLT or HPL all appear to show 'higher clinical effectiveness' (Prouza etl., (2013) or 'better outcomes for all parameters' (Ordahan et al., (2017), for HPL From a clinician's point of you I will say that I did not use LLLt in practice (mainly due to the issues highlighted in the Cochrane database). Having tried HPL though I have found, like the literature, much better outcomes I hope this is of some help Cliff


Tim, many thanks for this reply. As you said, it would be really helpful if other professionals could jump in, and provide some clinical/scientific insight.

In the meantime, i have another question for you, as i really respect your expertise, critical thinking and evidence-based approach.

1.)Namely, what do you understand to be the main therapeutic mechanism of action (LLLT) and what would be potential combinations of different mechanisms (cellular events) that have an interplay, lets say in the sub-acute stage of soft tissue (ligament) injury LLLT management?

2.)Your opinion on the cytochrome C-oxidase enzyme role and its ability to fascillitate ATP production together with better tissue oxygenation. This is the main commercial claim and in theory it seems pretty reasonable ... however, there have been some papers published recently suggesting otherwise:

3.) And lastly, what would be your insight (a simplified explanation, if possible:) of the role/change of Nitric Oxide conc.and intracellular Ca+ levels when it comes to therapeutical benefits of LLLT? Would that provide some different/complimentary explanation compared CcO enzyme role?

Looking forward to constructive debate Thanks in advance

Prof Tim Watson
Prof Tim Watson

Rok. Thank you for your query. There is a lot of controversy around out there with regards the High Power Laser evidence. I have looked at it, and certainly a LOT of the evidence cited - by the manufacturers - actually related to work done on LLLT (i.e. low power) - so on one hand they are saying that High Power is different - and then, on the other hand they are citing research from another intervention. The effect of laser light on the tissues is based on a lot of factors but primarily (a) wavelength and (b) energy - or, more properly energy density. The high power laser systems will certainly deliver more energy in less time - but I fail how that is 'better' other than treatment times will be shorter. The claims that it penetrates 'deeper' into the tissue - and I can't see this directly supported from the evidence that I have looked at. More energy will reach the tissues in less time, but I can't see that it goes further into the tissue. Anecdotally, I agree with you that there seems to be support for the modality - but that is not the same thing. Laser in general, and high power laser in particular are not my specialist fields. There are those on the forum for whom this is right up their street, so lets see what they have to say on the topic - I might have missed some critical evidence out there. The best that I have seen appears to say that if you deliver the same amount of energy at the same wavelength, the effects are the same (whether you happen to use a low or high powered device). Not sure that this resolves the issue in any way, but it might serve to spark an informed debate. Tim

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