Improved workouts / training etc too. The mile at that pace is a lot like a long sprint- which requires pretty different muscles / preparation. Look at how clo

Improved workouts / training etc too. The mile at that pace is a lot like a long sprint- which requires pretty different muscles / preparation. Look at how close the top high school kids are to breaking 4 and how many have. I don't think it can be explained away with their shoes and diet.