How deep does Red and NIR actually penetrate though the body?
This diagram is more like what you would find in peer reviewed published literature.
In several studies, the penetration ranges between 1mm to just beyond 5mm deep for both Red and NIR. Not much! Definitely not as much as those misleading diagrams!
Studies note that to optimize penetration they should also use higher intensities, skin contact, and continuous wave (not pulsing). Pulsing is helpful for penetration ONLY if excessive heating becomes a problem!
So it would be great if other panel companies would be honest about intensity so people can properly understand dosing and penetration. And at least acknowledge the disadvantage of being 6+ inches away. Oh yeah and not add pulsing just to make new false claims about it.
Some studies have found penetration up to 40-50mm when employing higher intensities (even with Red)! However, they note that high intensity can become detrimental to the skin and upper tissue. Which is where pulsing may be helpful.
And we know many people are getting great benefits with LED panels and parameters that don't directly penetrate as deeply as we thought.
So how does that work? Is it all placebo?
Certainly not, many studies understand that the penetration isn't as deep as we thought. And the benefits for the brain and deeper tissue could be explained through secondary mechanisms and systemic effects that bring the benefits deeper into the body.
So we don't need to get caught up trying to blast our brains with high intensity lights. We can use lower intensity and allow the body to do what it needs to do.