" The runner who may just have completed a fast 400 meter repetition at a sub-5-minute mile pace, may drop to an 8 minute mile pace for a recovery lap. The jog might be carried out in much poorer, looser form whose purpose is to "shake out" the body and maintain circulation to eliminate the waste products of exercise metabolism . Competitive running Perhaps the most basic of athletic contests, running races are simply contests to determine which of the competitors is able to run a certain distance fastest. Today, competitive running events make up the core of the sport of athletics. Running competitions have probably existed for most of humanity's history, and were a key part of the ancient Greek Olympics, as well as the modern Olympic games. 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. No Doubt Running 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. "

" 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. 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. There is a very strong consensus among the running and scientific community that all of those can be very effective in minimizing or recovering from running injuries. Running Sock Another injury prevention method that is very commonly recommended in the running community, but is actually controversial is stretching. While stretching is often recommended as a near requirement to avoid running injuries, the relevant medical literature does not represent as much of a consensus that it is effective. "