The engine: VO2max, threshold and running economy

Your engine is three numbers, not one. VO2max is the ceiling: the most oxygen you can use per minute. Threshold is how much of that ceiling you can hold for a long effort. Running economy is how much oxygen each kilometre costs you. VO2max sets the upper limit, but speed at lactate threshold, which folds in all three, is the best single predictor of distance running performance.¹

If you lift, I explain it like this: VO2max is your 1RM for cardio. A ceiling you can't hold, and every pace you run is a percentage of it.

The articles below are written for people who train both halves. They lean on lab data and say plainly where the data stops. Where a number comes from hybridAF's own scoring, like the VO2max cut points, it's labelled as our design choice, not published science.

Start here#

VO2max by age and sex: what the reference data shows sets out the US registry percentiles, why other charts disagree, and where our cut points sit against them, including where they're stricter.

How accurate is Apple Watch VO2max? And Garmin? is the one to read before you compare your number to any chart. It covers how far off a watch can be, and which way it tends to miss if you're fit.

How to raise VO2max without losing strength covers the interval research, the 4x4 trial, what adding intervals costs your lifts, and where the session fits in a lifting week.

Lactate threshold vs VO2max: which one HYROX actually taxes is for anyone who races. An hour-long event is decided mostly by what you can hold, not by your ceiling.

Running with more muscle: body mass and running economy answers a question lifters who run ask a lot: does the extra muscle cost you on the run, and why are per-kilo numbers a little harsh on heavier athletes?

Related reading#

If you don't have a VO2max estimate you trust, the VO2max calculator turns a recent race or a steady run with heart rate into one, with a range, and grades it against the same age and sex cut points the app uses; a hard race confirmed by heart rate carries the smallest error of its inputs. The hybrid athlete standards put the strength and engine cut points side by side, and the science page separates the published evidence from our design choices.