Exercise reduces risks for serious illness. Exercise reduces people's chances of developing and dying of illnesses such as heart disease. It does this by lowering illness risk factors such as triglyceride and overall cholesterol levels, while improving the level of HDL (the "good" cholesterol which is thought to reduce the risk of heart disease). Weight-bearing exercise and strength training activities help to maintain or increase bone mass, reducing a person's risk for osteoarthritis and associated bone fractures. Regular exercise also lowers resting blood pressure rates for hours after an exercise session is over. In addition, moderate exercise may significantly reduce the risk of developing type II diabetes. Arthritics who exercise often experience more strength and flexibility in their affected joints as well as a reduced pain levels. Furthermore, exercise may delay or prevent the development of arthritis in other joints. Regular walking of over a mile a day has been shown to reduce the risk of stroke significantly. Exercise even appears to reduce the risk of developing some cancers, especially cancers of the breast and colon.