Exercise Exercise doesn't have to be vigorous to offer health benefits. Aim for at least 30 minutes of moderate physical activity daily, or on most days of the week. Patellofemoral Pain Syndrome (Runner's Knee) Runner's knee occurs when the kneecap rubs against the thighbone as it moves. The condition can be caused by a structural defect or a certain way of walking or running. Preventing Sports Injuries Good preventive steps: Warm up before you work out, alternate days for exercising certain muscle groups, and cool down when you're done. Sports and Fractures Stress fractures are weak spots or small cracks in the bone caused by continuous overuse. They often occur in the foot after training for basketball, running, and other sports. Shin Splints Shin splints involve damage to one of two groups of muscles along the shin bone that cause pain. The location of the shin splint pain depends on which group of muscles is damaged. Exercise and the Aging Person Exercise is good for people of all ages. It helps lower blood pressure, reduces the risks for falls and serious injuries, and slows the body's loss of muscle and bone mass. Patellar Tendonitis (Jumper's Knee) Jumper's knee is also known as patellar tendonitis. It may be caused by overuse of the knee joint, such as frequent jumping on hard surfaces. Lumbar Strain (Weight Lifter's Back) A lumbar strain is an injury to the lower back, which results in damaged tendons and muscles that spasm and feel sore.