Both short, intense sprints and steady, moderate workouts boost teenage boys' stamina just as much after six weeks — either way, their bodies get better at using oxygen.

Older men in their 60s and 70s didn’t get better at using oxygen during exercise after three weeks of intense sprinting, but younger men did—so aging might make it harder for your body to improve aerobic fitness from short, intense workouts.

Doing short bursts of intense exercise for 12 weeks doesn't improve the maximum oxygen your body can use during exercise in people with excess body fat, even though they can exercise longer before getting tired.

Doing steady, moderate workouts might boost your heart and lung fitness more than super intense but short sprints, even though the moderate workouts take longer.

Doing short bursts of intense exercise might boost heart fitness more than steady, moderate workouts for people with heart disease — on average by a small but measurable amount.

When young and older men do short, super-intense bike or sprint workouts, the young guys get better at using oxygen during exercise, but the older guys don’t — their bodies just don’t respond the same way.