Researchers at Brigham and Women’s Hospital analyzed data from more than 650,000 people to find out if an active life translates to a longer life. What they found is pretty convincing: People who walk 75 minutes a week live, on average, 1.8 years longer than their sedentary contemporaries. It only gets better from there. Walking briskly for at least 150 minutes a week is associated with a 3.4-year gain in life expectancy, and 450 minutes a week tacks on 4.5 years. Hoofing it an hour a day to live four years longer? That’s our kind of math.