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 short bursts of intense exercise a few times a week for 12 weeks makes people with excess body fat able to exercise longer before getting tired, but doesn't significantly improve their maximum oxygen capacity.

Eating very few carbs and more fats for 12 weeks doesn't improve the maximum oxygen your body can use during exercise in people with excess body fat when measured in absolute terms.

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.

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.

Doing light, steady exercise like brisk walking regularly can significantly boost your heart and lung fitness—even if you're just starting out. That kind of improvement could lower your risk of dying from any cause by over 10%.