Chris Hadfield helps both NASA and the Canadian Space Agency study the health implications of space travel, so he knows a thing or two about keeping the human body in good shape. “In weightlessness, you literally don’t have to hold your head up. You can be the laziest person in the universe, and you will just decay terribly,” says Hadfield.

Fighting gravity by moving your body regularly is the best way to stay in shape. In space, Hadfield spent two hours a day harnessed to a treadmill or clipped to a stationary bike in order to exercise; but down on Earth, we have the luxury of using gravitational pull for resistance. “Instead of buying another piece of exercise gear, a new set of shoes and a gym membership, go for a walk or do jumping jacks, which need no equipment,” says Hadfield. “What you really need is impetus and discipline.”

If you want to learn more about Chris Hadfield and hear some of his best advice, check out our meet the May guest-editor page.