You can do anything that makes your heart and lungs work harder, such as walking, biking, jogging, swimming, fitness classes, or cross-country skiing. Mowing your lawn, going out dancing, playing with your kids -- it all counts, if it revs your heart.
If you don’t exercise and you’re a man over 45, a woman over 55, or have a medical condition, ask your doctor if you should avoid any types of activities.