If you follow health news, you’ve probably heard a lot about the benefits of intense exercise in recent months.

A September 2024 study found that high-effort physical activity reduces the risk of death from any cause. A study published in August found that high-intensity interval training, aka HIIT, helps stroke survivors rapidly increase their cardiovascular (or heart and blood vessel) fitness.

You can burn more calories by alternating high-energy cardio like jumping rope and burpees with periods of rest. Other recent studies suggest pushing yourself a little harder could help curb hunger, boost brain power, and reduce the risk of the most aggressive types of cancer. “Literally a few minutes a day can be beneficial,” said Martin Gibala, PhD, a professor of kinesiology at McMaster University in Ontario who’s studied HIIT for the past 20 years. And by “literally,” he means literally.

In 2022, he and his co-authors showed that people in a study who built up just 4.4 minutes a day of “vigorous intermittent lifestyle physical activity” – defined as doing something strenuous for a minute or two at a time – reduced their risk of dying from cancer, cardiovascular disease, or any other cause by 26% to 34%, compared to people in the study who didn’t do any. So … what’s going on inside our bodies during and after intense activity that makes it even healthier than a quieter effort? The short answer: The helpful effects of brief but challenging exercise begin with a complex biochemical cascade. Those signaling chemicals trigger extensive remodeling of your metabolism and physiology. That, in turn, leads to the ultimate benefit: higher cardiovascular fitness, which is the most important predictor of a longer, healthier life.

In a 2016 review on interval training, Gibala and co-author Martin MacInnis noted that “higher intensities of exercise elicit a greater metabolic signal than moderate intensities.” Gibala compares it to fuel efficiency when driving. If you give yourself plenty of time to reach your destination, you can drive at a steady speed and use a minimal amount of fuel.

But if you’re running late and drive like a maniac, your trip is a series of abrupt starts and stops. Each time you mash down on the gas pedal, you’re burning way more gas than you would typically need to get from one place to the next.

Doing high-intensity intervals is the human equivalent of driving like a bat out of hell. You rapidly use up your muscles’ stores of adenosine triphosphate (ATP), which is their primary energy source – their “gasoline.” ATP depletion triggers a protein called adenosine monophosphate-activated protein kinase (AMPK). AMPK helps regulate cellular energy and, in this case, flips the “on” switch for another protein, PGC-1a.