Four small models of the physics underneath a session. Touch them. Nothing here is a claim — it’s the plumbing, rendered honestly.
Supply and rate. Pressure brings more oxygen to the door; light speeds up the machinery inside. Turn them on and watch the energy rise.
Pressure raises the supply of oxygen; light raises the rate the cell can use it — near-infrared lands on cytochrome c oxidase and electrons move faster down the chain. Both at once make the most ATP. What that buys you isn’t a number on a screen — it’s more cellular energy, and the steadiness you tend to feel later.
The red blood cells are already full. Slide the pressure up and watch where the extra oxygen actually goes.
Hemoglobin’s already full — it can’t hold more, so the red cells don’t change. Pressure fills the plasma instead, dissolving roughly ten times more oxygen into the fluid your blood cells ride in. And plasma is what reaches the corners blood flow leaves short. We measure that reach — the point is the corner lighting up, not the number.
Biology runs on right amounts. Slide the input up and watch the benefit rise, peak, and then — past a point — fall.
Too little does nothing. The right amount helps. Too much stops helping — and can cost you. There’s no unit on that axis on purpose; the shape is the truth, not the digits. We measure, so you stay in the band that works for you.
There’s a band of light your body lets through. Slide across the spectrum and watch how deep each color actually reaches.
Below the window your skin soaks the light up; above it, the water in your tissue stops it. In between — roughly 650 to 1350 nm — light slips past the surface and reaches centimeters down, to the mitochondria waiting to use it. That band is why the light works at depth instead of just warming your skin.