Want to live longer? Lace up your sneakers, and start running! Because new research shows that for every hour you run – no matter how far or fast you go – you’ll add 7 hours to your lifespan. That may not seem like much. But if you consistently run for an hour, 4 days a week, it’ll eventually add up to more than 3 extra years.

To come up with these numbers, researchers from Iowa State University analyzed numerous studies on exercise and mortality, involving nearly 60‑thousand adults over a 15-year period. The result: When couch potatoes started walking or bicycling regularly, their risk of premature death dropped 12%. And if they started running, their risk dropped an additional 28%. And that was true even after researchers controlled for smoking, drinking, and a history of health problems, like obesity.

So, why is running so good for our longevity? Because aerobic fitness helps fight two of the most common risk factors for early death: High blood pressure and dangerous visceral belly fat. Plus, running puts a moderate amount of stress on the heart which, surprisingly, can make us less prone to heart attacks. In fact, researchers discovered that if every non-runner in the study had taken up running, there would have been 25% fewer fatal heart attacks.

But don’t go overboard with the running. Four hours a week is the magic number. Researchers aren’t sure why, but running MORE than that does NOT extend our overall life expectancy any further.