My Sprint Form

I thought adding more stuff to my last thread would be kind of unorganized so I made a new one.

http://www.youtube.com/watch?v=MefyAqizdLI

The main thing I noticed about this video was the fact that I definitely wasn’t stepping over my knee when I was sprinting and I feel like this is a problem I’ve been having lately. Does anybody know why I might be having problems stepping over? Is it usually a flexibility problem or a problem with force production or something else?