You would hope that no Olympian needs extra motivation to win medals, but BMX racer Arielle Martin, 27, has some just in case. Four years ago, she was ranked eighth in the world and needed only to finish a world-championship race a few weeks before Beijing in order to clinch a spot. And she was comfortably in second place when she came in to a jump too fast, overshot the landing and crashed. "It came down to one race, one lap, and I blew it," Martin says. Her crash caused the U.S. team to drop out of the top four in the world rankings, which meant it could send only one racer instead of two, and that racer was her close friend Jill Kintner. "It was pretty devastating," Martin says. "I was top eight in the world and didn't make the Olympics." She had to reset her goals and prepare to wait four long years. "The day after Beijing it felt like it would be a lifetime away until London," she says. But she rededicated herself to racing. Two months after the Olympics, she won a World Cup series race. "And now I'm just days away from being there."