Benefits of running

While there is the potential for injury in running (just as there is in any sport), there are many benefits. Some of these benefits include potential weight loss, improved cardiovascular health, increased muscle mass, increased bone density, and an improved emotional state. Following a consistent routine of running can increase HDL levels, reducing the risks of cardiovascular disease.[citation needed] Running, like all forms of regular exercise, can effectively slow or reverse the effects of aging.

Running can assist people in losing weight and staying in shape. Different speeds and distances are appropriate for different individual health and fitness levels. For new runners, it takes time to get into shape. The key is consistency and a slow increase in speed and distance. While running, it is best to pay attention to how one's body feels. If a runner is gasping for breath or feels exhausted while running, it may be beneficial to slow down or try a shorter distance for a few weeks. If a runner feels that the pace or distance is no longer challenging, then the runner may want to speed up or run farther.

Running can also have psychological benefits, as many participants in the sport report feeling an elated, euphoric state, often referred to as a "runner's high". Running is frequently recommended as therapy for people with clinical depression and people coping with addiction.
In animal models, running has been shown to increase the number of newly born neurons within the brain. This finding could have significant implications in aging as well as learning and memory.

http://en.wikipedia.org/wiki/Running