2026 · 05 · 18
Where it began
The argument that started it all, and the decision to stop debating and start building.
Indirect Calorimetry Made Personal
Propoxity is a consumer-grade metabolic system that measures VO₂max and both lactate thresholds. The same science as a sports lab, built to live in your gym bag.
VO₂max
Maximal oxygen uptake, measured breath by breath.
LT1 & LT2
The ventilatory thresholds that define every training zone.
Under $300
Lab-grade accuracy, without the lab-grade price.
The origin
It started as an argument.
Deep in Ironman training, with one of us chasing a sub-4:15 mile, we kept circling the same disagreement. One of our closest friends was convinced our Garmins were completely inaccurate when it came to VO₂max. Wrist estimates, he insisted, weren’t measuring anything real.
Half to prove a point, half to finally get my hands into real hardware and software integration, I set myself a constraint: build something that measures VO₂max properly, from actual breath gas exchange.
That constraint is still the whole philosophy. Prove the measurement first, make it comfortable second. The point was never to look good on a wrist. It was to tell the truth.
The build log
Build log.
The honest, unpolished record of getting Propoxity from an argument to an instrument. Updated as it happens.
COMING SOON
The first Propoxity system is in the workshop.
propoxity.com