If you're interested in the science behind it, and also a really neat story, pick up "Born to Run: A Hidden Tribe, Superathletes, and the Greatest Race the World Has Never Seen" by Christopher McDougall. He was a runner who kept injuring himself in running shoes and also a journalist. His doc one day told him that humans just weren't designed to run; being stubborn and getting paid to find interesting stories anyway, he went in search to see if this was true.
One of the more interesting things to come from this is the earliest form of hunting, called endurance hunting. Our ancestors would literally just chase a deer or elk or whatever until the animal collapsed from exhaustion, and then just brain it with a stick or rock or whatever.
Check it out. These guys have shoes but ancient man did not, and our old hunting technique was apparently to run our prey to death:
http://www.youtube.com/watch?v=826HMLoiE_o