10 Facts About running surfaces That Will Instantly Put You in a Good Mood
http://josueekyn284.angelfire.com/index.blog/1659689/why-you-should-focus-on-improving-running-surfaces/
Asphalt - Now you would think that asphalt is simply as bad as concrete, however it is not. It's actually about 8 times "softer". The genuine problem with running on asphalt roadways is not the solidity, but the