What red light actually does, and how well we know it.
This page is the long version. It walks through the proposed mechanism step by step, shows what the peer-reviewed literature supports, marks where the evidence is strong and where it is thin, and links every claim to its source so you can check the work yourself.
Follow one photon.
From leaving the LED to changing something inside a cell. Tap each step — the diagram follows along.
It leaves the diode
An LED emits a narrow band of wavelengths rather than the broad mixture of daylight. That matters, because what happens next depends almost entirely on wavelength — how deep the light travels, and which molecules can absorb it.
See the source →Why wavelength decides everything.
Drag the slider. The tissue diagram shows roughly how far that colour of light gets before it has faded to one percent of what arrived — the depth figures come from a published computational model of light in skin.
Depths are the 1%-intensity criterion from Ash et al. (2017), a Monte-Carlo model of light in skin. That study covers 300–750 nm; anything above 750 nm on this slider is shown as beyond its modelled range rather than given a number we cannot support.
What the light is thought to hit.
The leading explanation is that light is absorbed by an enzyme in the mitochondrion. Pick a part of the mechanism to read what it does — and how firmly it is established.
What the studies actually found.
Graded by the strength of the human evidence behind each one. Open any row for the detail and the citation.
Where this is still uncertain.
Every one of these is a real limitation in the literature, and knowing them is part of reading the evidence properly.
More is not better
Photobiomodulation shows a biphasic dose response: too little light does nothing, and too much can undo the effect entirely. Dose is the whole question — a longer session or a more powerful device is not automatically a better one.
The studies are not comparable
Trials differ enormously in wavelength, power, dose, distance and timing. A meta-analysis of 39 muscle trials rated the quality of evidence from very low to moderate and called for further investigation. Results from one device do not transfer to another.
The mechanism is a model
Cytochrome c oxidase absorbing light and releasing nitric oxide is the leading explanation and it is well supported — but it is still a proposed mechanism, other pathways such as light-gated ion channels are under active investigation, and "proposed" is the honest word.
None of this is evidence about a Rubaris device.
Everything above is evidence about red and near-infrared light as a field. It is not a measurement of any product we sell. Each device publishes its own wavelengths and specifications on its own product page. No study on this page should be read as a claim about what a Rubaris device will do for you.
Why 660 nm and 850 nm.
Between roughly 650 and 950 nanometres there is a stretch where haemoglobin has stopped absorbing strongly and water has not started — the so-called optical window. Light in that band travels further into tissue than anything on either side of it, which is why effectively every photobiomodulation device converges on the same region.
660 nm sits at the red end of that window. It is absorbed comparatively shallowly, which is why the skin and hair literature — collagen density, wrinkles, follicles — is built on red wavelengths. 850 nm sits at the near-infrared end. It scatters less and reaches further, which is the rationale for using it where the target is below the skin. The muscle meta-analysis found its positive results across 655–950 nm, which brackets both.
The honest caveat: "further" still means millimetres. The deepest figure in the modelling study on this page is 5.4 mm, and that is at the 1% level — the point where ninety-nine percent of the light is already gone. A reach quoted in centimetres is not describing the same measurement.
Every claim on this page, and where it came from.
Links go to PubMed or the publisher. Where a finding is from a meta-analysis or systematic review it is marked, because those carry more weight than a single trial.