You don’t have to take up a new sport. Just work in the garden or take a brisk walk around the block. Each week, aim for at least 2 1/2 hours of activity that gets your heart going. And throw in some moves for your muscles, like push-ups or sit-ups, a couple of times. It can help you feel better, look better, and think better, too. It also helps prevent diabetes, high blood pressure, and heart disease. But check with your doctor before starting any new exercise plan.