Fatigue means that you cannot lift the weight anymore without resting first. Marathon runners don't train to fatigue. They run 10 or 20km. They could still run

Fatigue means that you cannot lift the weight anymore without resting first. Marathon runners don't train to fatigue. They run 10 or 20km. They could still run more if they wished. The reason sprinters are more muscular is that they do a lot of strength training outside running, while marathon runners don't -- although there's some evidence that doing more than they do now would improve results.