O, the irony. Researchers at Nike have found a way to improve your running speed. The catch? You have to train in bare feet. The idea is that barefoot running strengthens feet that have been coddled, pampered, and isolated from their traditional contact with the ground. That won't sell a lot of shoes, though, so the company came up with the Free 5.0, which provides all the benefits of being barefoot without the distracting shards of broken glass.