Look at the back arm in this photo:
larger original – flickr – by foto-plaul
That’s a pet peeve of mine. If a runner straightens the arm at the back, it tends to slow the sprint. (The legs can only turn over as fast as the arm swing.)
With kids I call that common error, “throwing money away”. She needs more drills for correct arm action.
I like the front arm position, happily.
