Originally Posted by zaphod1
Hi Tutt,I’m curious to your take on the advantages/disadvantages of NIR vs FIR. The following page (loaded with references to the literature at the end) seems to suggest some advantage of NIR over FIR - sun pumps out more NIR, humans have evolved to utilise it more than FIR, yadda yadda etc. Plus they cite some NASA study claiming that NIR penetrates human tissue up to a depth of 23cm! (I assume this probably uses a million watt emitter that also reduces flesh to a carbonised lump in the process :-) ).
https://livingl ovecommunity.co … ight-therapies/
Cheers!
Well there are several things in this post. Let me tackle them one at a time. Have humans evolved to utilize the most abundant light? That’s a pretty safe assumption even without scientific proof, and definitely NIR is more abundant than FIR. Did NASA run an experiment that showed 23cm depth penetration into tissues? Yes, they did. Does this mean that we should be using NIR instead of FIR? No. it is widely recognized that FIR produces more heat deeper in the tissues than NIR. Keep reading if you want the explanation.
Let’s take a step back and look at physics and the literature. There is no doubt that our bodies have incredible adaptive response to the immediate environment. In terms of evolution, protection against and utilization of light energy is among the most important. For example, on the other side of the visible spectrum, we have the ability to darken our skin within hours of the cells sensing an abundance of UV light. This is a defense against the damaging effects of UV light. Simultaneously, our skin utilizes UV light in creating Vitamin D. So our bodies recognize that light radiation is harmful, but necessary. Now jumping back to the red end of the spectrum, both visible and invisible light on this end trigger cellular response. Much of it is still not understood, but some of it is well documented now. It is becoming very well established that light therapy on the red end of the spectrum is overall quite beneficial. The cited study by NASA was driven by the discovery that astronauts in zero gravity experience cellular degradation because cell growth is triggered by gravitational forces. They ran studies to show that light therapy could be used to trigger cell growth in microgravity environments. It worked, and they shared the findings. In their study they used a high sensitivity spectroscope to detect light penetration through the tissues. They found that they were able to detect some light signal on the opposite side of the leg muscle, which was 23cm thick. They used LED light in both the red and very near infrared range (680nm, 730nm, and 880nm). FYI, 880nm is just barely outside the visible range. This is very important as we will see in a moment.
The source of your article is in the business of selling a NIR product for a specific purpose. They are selling light therapy for overall tissue health, specifically in the NIR range, so it is in their best interest to promote that product. Once one of them cited the NASA study, all the other sellers of NIR treatments grabbed onto it. None of them are fairly representing it. The reality is that we are not primarily using this light to trigger cell growth like NASA did. We are using it primary for generating heat. What NASA didn’t discuss, but others have, is that depth of penetration is highly correlated with power. In their case, they needed to use intense LED light to achieve deep penetration of visible and nearly visible light. But if they were using it to deep heat the tissue, they wouldn’t have used visible light. Also, LED technology is abundant and robust in the visible and nearly visible spectrum, which made it handy to construct blankets out of for the astronauts that would hold up to abusive environments.
Once you get up into the true infrared range, you have to be very careful with power levels, because light above the visible red range begins to generate heat energy. If they would’ve used FIR at high power for cell growth triggering, it would’ve risked heat stroke and surface burns. They weren’t about to wrap astronauts in high power deep heating blankets for long periods of time. They didn’t even need to test this aspect because it is already a known phenomenon. When you want to quickly heat up that frozen burrito, what’s the fastest way to do it? Toss it in the microwave. Why? Because long wavelengths travel through materials, generating heat along the way. Microwaves are generally ideal for this in terms of balancing heat generation in food items at the lowest possible power input. Go even further up the spectrum and you reach radio waves that can literally travel through buildings relatively undisturbed. So the point is that we already know that longer wavelengths penetrate deeper through the tissue. Radio waves at high power would literally cook you all the way through at an even rate. Anyone arguing otherwise is just trying to sell something.
Now jumping to the other literature. FIR not only penetrates deeply, but has the ability to actually provide measurable heating to the tissues up to a depth of about 2cm. Tests measuring relatively high power NIR repeatedly showed that less than 2% of the energy made it to a depth of 2cm. Power necessary to actually heat the tissue at that depth would’ve charred the surface tissue. Conversely, FIR can provide heat to those depths without surface burns. Microwaves can perform that function even better, heating the inside and surface nearly equivalently in some tissues, but the microwave emitter is relatively dangerous and not very useable. So in PE we are left with FIR at the moment as the deepest heat treatment utilizing electromagnetic waves. Because of this, we have jumped over into sound waves as a reliable way to generate heat in deep tissues. Because US devices at requisite power levels are readily available in handheld form.
The biggest problem with sound waves is that they need a medium to travel through. So the US sound head must be in perfect contact with the tissue. I keep working on jumping back over into the EM waves realm, because it offers the potential benefit of being contactless. Meaning that we can hover the wave plate over the area and it will generate heat much like a heat lamp. But in order to do this, we need to jump into the radio frequency realm, so I haven’t quite figured it out yet for PE. Although, the fat removal industry has already solved the problem, and the RF devices are absolutely the most effective non-invasive fat removal methods available.