Tonight I was in the rather unfortunate position to sit through a chiropractor doing a series of demonstrations of how low-level laser therapy could be used to, “fix,” asymettries in leg muscles of a cycle pedal stroke. :dubious:
Basically, he would do this demo where he could push down or up on a leg on one side against a person’s maximum resistance, but couldn’t do so on the otherside. Voila, after 30 seconds of low-level laser therapy, this asymetry was resolved and he couldn’t push up or pull down or shove aside either leg. I was a little dubious of course, and he frankly went on to make a fool of himself by claiming that this therapy could even be done through clothing because, “those photons could penetrate so far that they aren’t only going through a shirt, they’re going through the table, the floor, and two feet into the dirt.” Right, at 635 nm.
Anyway, I’ve decided to Google around on it, and to my marked suprise, I’ve found that there in-fact do appear to be some well-controlled double blinded studies on LLLT that show that it does indeed seem to have some effects.
Here’s one that shows reduced inflamation in mice:
In periodontal work:
Yet you also have a number of studies that show no effect:
Well, I was frankly suprised to see that it had any effect on anything, but what do the erudite individuals of the SDMB think about the theapy. Can it actually alter neuromuscular recruitment as my chiropractor claimed, and if not, what is it good for? Also, can someone propose a realisitc model for how LLLT might work if it actually does?
I can’t imagine how dim laser light could solve any medical problems that regular sunlight couldn’t.
I think you can safely ignore anything that chiropractor said about it, though. Visible light doesn’t penetrate through tables and floors, last I checked. If it did, you wouldn’t be able to see the table.
Right, I’m sure of that, so that’s when I wrote off this chiro, but I imagine that these lasers still do penetrate a few cm’s, like putting your hand up to a flashlight, etc. And no, I can’t imagine how they work either, but apparently they do affect some biological processes.
The showmanship was pure and obvious quackery, as, pretty much, were the assertions about the penetration of photons (I say pretty much because absorption of photons is a statistical thing and it is probably incorrect to say that none of them ever penetrate the table…
Anyway… why might it work? Well, assuming the research is reliable, one thing that might be a factor is that vitamin D synthesis takes place in the human skin in response to light - usually sunlight, but I’m not sure exactly what component of sunlight is most responsible, and whether this is provided by the laser therapy.
I don’t know anything about (does the quote thingy with his fingers ala Dr Evil) L A S E R S fixing boo-boos, but I’ve seen those magical magnet guys at trade shows pull this same snake oil trick.
“Stand on this magnet insole I’ve taped to the floor. Wow, I can hardly push your arms down now. See how much they’ve helped you already?”
I recall seeing some medical laser treatments exhibited at an alternative medicine exhibition in London about 25 years ago, so the concept isn’t new. I’m damned if I can remember how they were supposed to work now.
As luck would have it, IR (relative) laser diode expert. Laser light is different from sunlight in that:
It’s light of just one wavelength;
It’s polarised.
Now the optical power of sunlight is about 1000W to 2000W per square metre. A laser pointer is about 2mW, and a 650nm laser in a 16X DVD recorder is between 150mW to 200mW. That doesn’t sound like a lot, but 2mW concentrated into a very small area has a much greater power density than sunlight, which is why a laser beam can burn out your retinal cells if you catch an eyeful. And a 200mW laser is very bright, and guaranteed to damage your eyes.
Absorbed light increases the temperature of an object, and given that human flesh is a bit translucent a laser beam would have no problems penetrating to reasonable depths, heating any cells or pathogens in its path. Aside from burning flesh, I can only guess at what effect this has on the body. It may kill pathogens while only mildly warming healthy cells, it may stimulate the immune system, it may stimulate certain free-radical chemical reactions. I dunno.
Another thing you can do with semiconductor lasers is modulate the brightness at very high speeds. If the laser is modulated, there may be a key frequency that would have some effect at a cellular level - it would cause the cells to vibrate slightly with the rapid heating/cooling of the laser pulses.
On thing to consider with laser therapy is that the laser spot is very small relative to the human body. What works on a mouse might not scale up!
Oops, did I say laser light was polarised? I meant coherent, not polarised. You can polarise laser light with a polarising filter, but they’re not fitted to laser diode modules as standard. You’ll forgive me my old-age brainfade.
Coherent light is very special, and gives a very strange dimply effect when reflected off an uneven surface due to the static nature of the areas of constructive and destructive interference. This may have medical effects when used on flesh under certain conditions, or it may not.
Optics guy checking in here. I’ve never heard of this before, but it sounds like a scam to me.
Laser light is coherent, monochromatic (or at least of a more restricted range of wavelengths), directional and generally more intense than other forms of light. It can be generated as polarized in many cases, rather than polarizing and existing beam (and throwing half the output away).
There are several probes that send light through the skin and look at the transmitted light out the other side (as in the flaslight example) or at scattered ligh returning. In many cases, the light doesn’t have to be a laser at all. They’re making disposable oxygen meters from blood that consist of an LED and a detector mounted on tape that you tape around a finger.
There are some laser treatments in which laser is light is shone through the skin or, more commonly, piped in via a fiber optic. These can be used to remove blockages in blood vessels, or to irradiate tumors. These are pretty special cases, though. They’re high power lasers, and sometimes the tumor or whatever has been senstizede with injected or injested chemicals. Not at all like what this sounds like.
The body uses sunlight to facilitate the making of Vitamin D. Too much sun will cause your skin to tan. Aside from the mechanism of vision and these I don’t know any bodily processes that use or require light, so I have no idea what low-level laser treatment can be doing. The laser wavelengths are already present in daylight that’s already getting into your skin, if not at as high a level, so it’s not clear that this is adding anything. Finally, I’d like to note that it’s not ecven clear to me that throwing extra light levels into the innards of the body is necessarily good, or necessarily not dangerous. I don’t see how it would be, just sayin’ that the body doesn’t “expect” light levels (or higher light levels) there, and so hitting it with light might a=have unintended and possibly not-good effects.