Aerobic exercise, which requires oxygen, elevates heart rate through sustained movements of the body at moderate intensity. Activities such as brisk walking, swimming and stationary bicycling are considered aerobic exercise. There is a long list of diseases associated with a sedentary lifestyle, e.g., heart disease, obesity and osteoporosis. The risk of developing these disorders can be reduced by regular aerobic exercise. Being in pain doesn't mean you should neglect overall health and well-being.
For people in pain, water exercises can be especially relaxing because you lose about 70 percent of gravity's effect in water. Since movement is so much easier in water, there's a tendency to exercise longer and harder. It's always best to start out low and slow.