Staying fit is important. Even if it seems enjoyable to lie on the couch and devour hours of YouTube videos on your iPad, science says you’re actually happier when you exercise. Fortunately, gadgets can fit in with your gym routine, and the right apps can even make it better. We’ve tested dozens of fitness apps, including ones that can help you train for a marathon, stick to a diet or do a downward-facing dog pose with the precision of a yogi. If you’re serious about getting into shape, here’s what you should download first.