Holmer adds durability as a fourth endurance predictor
The standard three lab numbers are measured rested, and Holmer says that is the problem.
Brady Holmer says the usual three predictors of endurance performance are missing one, and the missing one is durability.
He was replying to a post from Wendi A. Irlbeck, who listed the three main predictors as VO2 max, economy and lactate threshold. Her post spells each one out. VO2 max is the maximum amount of oxygen your body can take in, transport and use during intense exercise. Economy is how little oxygen and fuel you need to hold a given pace or power. Her example is a runner with a world-class VO2 max and lactate threshold who still ends up slower than a more economical runner with slightly lower numbers, because poor form and excessive bouncing burn more energy at the same pace.
Holmer's addition is durability, which he describes as how long you can hold onto your VO2 max, economy and lactate threshold during prolonged exercise. His framing is blunt. Fresh you is not fatigued you.
Why it matters for a marathon
All three of the standard numbers get measured on a rested athlete in a lab. A marathon is not decided rested. It is decided hours in, when the pace that felt easy at 10 miles costs more oxygen and more effort at 20. Durability is the word for how much of your fresh self you still have at that point.
Holmer's point is that two runners can test the same and race very differently. If you line up next to someone with identical lab values but better durability, he says, you lose.
If you line up next to someone with identical lab values but better durability, then you lose.
What it actually means
This is a framing argument between two people on X, not a new study. Holmer does not cite data here and does not say how to train or measure durability. It is also not a knock on the other three numbers, which Irlbeck's post explains in detail and which Holmer does not dispute.
It is a useful reminder that a lab profile describes you at your freshest, and that the last hour of a long race is where races are actually sorted out.
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