Aerobic workouts can be performed outdoors or indoors. A simple aerobic workout like running may be the best choice. It requires no equipment and the intensity can be controlled by your pace. If you haven't been active, take it slow. Go for duration, not speed. Combine walking and running. Be sure you warm up by walking at a brisk pace for 5 to 10 minutes. Stretch after you run and not before. During the summer months stay hydrated by consuming at least 1 liter of fluid.