The list of studies that show that aerobic exercise prevents or reduces the occurrence of cardiovascular disease is so long that it would take this entire article and probably five others just like it to review all of the research. One of the most important is one of the earliest. In a study of more than 13,000 men and women, it was shown that the least fit individuals had much higher rates of cardiovascular disease than fit individuals -- in some cases, the risk was twice as high. Aerobic exercise works in many ways to prevent heart disease; two of the most important are by reducing blood pressure and allowing blood vessels to be more compliant (more compliant means that they become less stiff and it's less likely for fat to accumulate and clog up the vessels). Results like these have been proven over and over again.
4. It eases joint pain. Several studies have found that walking reduces arthritis-related pain, and that walking five to six miles a week can even prevent arthritis from forming in the first place. Walking protects the joints — especially the knees and hips, which are most susceptible to osteoarthritis — by lubricating them and strengthening the muscles that support them.