Reader-funded, in development
What Your Watch Isn't Telling You
A handbook on training-watch metrics: what each one actually measures, when it lies, and what to do instead. Built on our studies of 81,000 activities and 375,000 days of training data.
The same research behind the free studies on this site, assembled into one coherent, practical read.
The race predictor is a ceiling, not a target
Why the number is 20–23% ahead of your training reality, within 0.6% on race day, and how to train off it without overcooking every week.
Readiness scores account for load. They do not forecast you.
What 5,136 runs say about Training Readiness, what the score is genuinely good at, and the morning decision process that beats it.
One recovery signal wearing three outfits
Body Battery, HRV status and sleep score move together because they are built from the same inputs. How to read them as one signal, not three confirmations.
VO2 max: ignore the number, use the line
The estimate cannot be verified against a lab, but its slow trend is useful. What moved it, and what did not, across a year of data.
Zones your body actually agrees with
Why default heart-rate zones are wrong for most people, and the field tests that fix them for running and cycling.
When to ignore the watch entirely
The situations where every score above breaks at once — illness, heat, altitude, life stress — and the low-tech signals that still work there.
$29 when it ships. Nothing today.
We are gauging demand before we write it, which is the honest version of a pre-order. Leave your email and you get first access at $29 when it is ready, plus the first chapter free. No payment now, no obligation later, and if we decide not to ship it, you have lost nothing.
Why reader-funded? Because it is the only revenue model that does not create a reason to soften a finding. Our research pages and calculators carry no commercial links, ever; selling our own work directly to you is the trade-off we chose instead. How we make money spells out the full rules.
Every claim in the handbook traces to a study you can read for free in the research library. The handbook is the assembled, practical version — the free material is not crippled to sell it.