Blog

Articles on training physiology, fitness data and how to make sense of the numbers.

Nov 4 · 10 min read

We track everything. But do we really understand our fitness?

Wearables give endurance athletes plenty of fitness data. What steps, heart rate, pace, calories and oxygen uptake estimates can and can't tell you.

Sep 17 · 4 min read

No hoses, no metabolic cart. Here's the physiology behind how the ARO2 sensor pod turns a single sealed breath into live VO2, ventilation and RER.

Sep 11 · 2 min read

Founder and CEO Matthew Behr on ultramarathons, why AeroCardia exists, and building a device that measures instead of estimates.

Aug 20 · 4 min read

What three weeks of racing at the limit of human endurance teaches the rest of us about VO2 max, pacing, and training.

Jul 27 · 4 min read

How VO2 max is measured, what an elite score looks like by age and sex, and the training protocols that actually move it.

Jul 13 · 3 min read

What VO2 max is, why it matters for endurance training, and how to measure it, in the lab and on the go.