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.

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.

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 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%.

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.

After just three weeks of short, intense bursts of running, older men had less of a biological marker in their blood that signals stress or damage in the body—this might mean their bodies are under less strain as they age.