" Events are usually grouped into several classes, each requiring substantially different athletic strengths and involving different tactics, training methods, and types of competitors. Running affects not only the body, but the mind as well . Runners who finish a great run are often said to have a "runner's high" - a strong feeling of accomplishment and pride. Some sources point to the origin of a runner's high being increased endorphin production as a result of exercise. Running injuries There are many injuries associated with running (due to it being a high impact activity). Common injuries are "runner's knee" (pain in the knee), shin splints, pulled muscles (especially the hamstring), "jogger's nipple" (soreness of the nipple due to friction), twisted ankles, and Iliotibial Band Syndrome. The most common running related injuries are due to over-use. Nike Running Camp Repetitive stress on the same tissues without enough time for recovery or due to improper form or muscle imbalances, leads to many of the above. Generally these can be minimized by warming up beforehand, wearing proper running shoes, improving running form, performing strengthening exercises, and getting enough rest. "

" Aerobic fitness, or the ability of the body to utilize oxygen, is important to have to complete the long distances. Anaerobic fitness, that is, the body's capability at responding when there isn't enough oxygen for the muscle, is necessary to charge up hills and past competitors on the finish line. A common saying for runners is that the sport is 90% mental. Recreational running became popular due to high-profile runners such as Steve Prefontaine. Race courses are usually held on the streets of major cities and towns but they could be on any sealed road. Most road races are either 5 km (3. 1 miles), 10 km (6. Nike Running Sneaker2 miles), half-marathon (21. 097 km, 13. "