Exercise stretches muscles and joints, which in turn can increase flexibility and help prevent injuries. Exercise may also improve balance by increasing strength of the tissues around joints and throughout the body, thus helping to prevent falls. Weight-bearing exercise, such as brisk walking and weight training, strengthens bones and helps prevent osteoporosis. Exercise often can improve function and reduce pain in people with osteoarthritis, although regimens must be developed specifically for each person, and exercises that put undue strain on joints, such as jumping and running, may need to be avoided.