Isn't any running unsustainable though ?

Not really. Google ultramarathoning, Humans are incredibly well designed to run long distances at a sustained pace, it's like the one other thing we rock at better than other animals other than intelligence.

A sprinter is wasted after 100m. A marathon runner is wasted after 26.2 miles. Then there are the ultra marathoners. I believe the analogy holds.

Humans evolved to be really good at long distance running and given proper training, time and discipline you can run an absurd distance compared to most mammals.

Sprints also have a specific meaning in Agile/Scrum vocabulary which should be pretty common around here. That's like suggesting github promotes physically aggressive behavior because it's centered around pushing. Nothing about a sprint in Scrum terminology is meant mean an unsustainable pace.

'I don't know what you mean by "glory",' Alice said.

Humpty Dumpty smiled contemptuously. 'Of course you don't — till I tell you. I meant "there's a nice knock-down argument for you!"'

'But "glory" doesn't mean "a nice knock-down argument",' Alice objected.

'When I use a word,' Humpty Dumpty said, in rather a scornful tone, 'it means just what I choose it to mean — neither more nor less.'

-- L. Carroll