Ah, look at this happy, healthy individual. Sure, he could be watching tv on the couch, enjoying a bowl of ice-cream with cheetohs sprinkled on top, feeling a little more gravitational pull. But why would he want that? Look at the joy in his face!
As he looks at his watch, he realizes he did not enjoy his run enough - he is running out of time to meet his goal! He must run faster! That will make him healthier, pushing his knee joints and cardiovascular system to the brink. If you're not risking injury, you're not being healthy. If you're not thoroughly emaciated, you're a threat to yourself and the entire health system.