A competitor to Nike's throne claims to have built the fastest shoe on the planet. Hard to believe? It brought receipts.

Puma claims the Fast-R Nitro Elite 3 is its "fastest ever running shoe," primed for use in the London and Boston marathons.

Puma Fuse is a workout shoe ... vying for the title of best workout shoe. Making shoes like this is not the same as trying to construct the best running shoes. They need to be stable enough ...