With your feet hip-width apart, take a large step forward with your left foot. Plant the foot, then slowly bend the left knee to a 90-degree angle with your back knee lightly touching the ground. Push up with your front leg to return to the starting position, then repeat on the other side. Because exercising your leg muscles helps increase blood flow to the heart and forces it to work harder, lunges are a good part of a cardiovascular routine (and they can help prevent varicose veins!). Daily dose: Ten to 20 reps, alternating sides.