VO₂max, lactate threshold, training zones, and fueling — the same model the sports-science labs use, built entirely from your own data. Start for free with just 4 simple time trial efforts, or go deeper with lactate testing and a coach-run in-person option.
Four max efforts (15 s, 3 min, 6 min, 12 min) and your full metabolic profile is built in your browser — VO2max, training paces, and more. No needles, no equipment, no payment. The same model the labs use, estimated from your own power and pace.
Free with your account · estimate, not measurement
The power-only profile is estimated from sprint power and max effort — useful but rough at the edges. The measured-lactate profile is built entirely from your own blood data, sharpening every downstream number — thresholds, fat-burning peak, and zones. Same model, real measurements underneath.
An Endurance Science Labs coach brings the meter, the strips, and the experience. We run the full sprint + step-test protocol with you and walk through your results face-to-face. Boulder area; Denver-area travel by arrangement.
esMetabolicLab implements the Mader/Heck bioenergetic model of human exercise metabolism, first published in 1984 by the German Sport University Cologne group. It's the same family of model that commercial tools like INSCYD, Aerotune, and Sentiero are built on.
What's different here: the math is open, the assumptions are surfaced, the implementation is documented, and your data never leaves the browser. The trade-off is honesty about what the model can and can't tell you — see "What this tool can't tell you" below.
The Mader model assumes a standard active-muscle fraction (~28% body mass) and standard Hill kinetic constants. Individuals vary, and the model was calibrated primarily on trained European male cyclists. Sex-specific validation in the published literature is thin.
VLamax has known reliability issues — within-subject variability of 5–15% between sessions is typical. A single measurement is a snapshot, not a permanent reading.
The model captures the steady-state metabolic balance well. It is more approximate for non-steady-state efforts (intervals, surges, tactical race dynamics).