Everyone has a plan, Mike Tyson famously said, until they get punched in the face. The endurance athlete’s version of that dictum might be: everyone has a great VO2 max and an efficient running stride until they’ve run 20 miles. How you fare in those final miles depends, in large part, on how steeply these factors have declined over the course of the race.
This is the fundamental premise of “fatigue resistance,” an idea I first wrote about back in 2021 that is currently one of the hottest topics in endurance science. The old view was that you could run some lab tests to determine an athlete’s VO2 max, lactate threshold, and running economy (or an equivalent measure of efficiency for other sports) and calculate their predicted finishing time. The new insight is that these factors change as you fatigue—and crucially, they change more in some people than others. Having good fatigue resistance, then, is the ”fourth dimension” of endurance.
So far, most of the research on fatigue resistance—which is also called “durability” or “physiological resilience”—has focused on demonstrating…
