M.S.
Hi Angela,
I am afraid I haven't anything helpful to say about the gravity defyers. But for running shoes, really nothing can beat going to an actual running shop and getting help. Here is a link to Hanson's Running shop's site (which honestly, I have never used them online ... but it looks like they sell online too) http://www.hansons-running.com/ But I can say -- in person -- I can't speak highly enough of their staff. I am not a hardcore runner, so their advice was extra helpful to me and they really understood my needs and judged my foot falls and everything! All the staff are highly qualified and just so nice. They have a locations in Utica, Royal Oak, Lake Orion and Grosse Pointe Shores. Good luck!!