For endurance athletes like your marathon runner, this is certainly the case. Strength and power athletes can certainly expend far more energy in a shorter time

For endurance athletes like your marathon runner, this is certainly the case. Strength and power athletes can certainly expend far more energy in a shorter time than someone who is less fit. It's a bit of a paradox where the better shape you are in, the sooner you can tire yourself out. From everything I've read, it certainly seems possible to reach oxygen depletion in a very short period of time. https://mobile.nytimes.com/blogs/well/2016/04/27/1-minute-of-all-out-exercise-may-equal-45-minutes-of-moderate-exertion/?referer= https://mobile.nytimes.com/blogs/well/2016/04/27/1-minute-of...