Radcliffe, 31, combines extreme training with breakthrough technology. Most of her practice sessions are logged at altitude near Font Romeu in the French Pyrenees or in Flagstaff, Arizona, where running in the thin alpine air boosts the oxygen-transporting red blood cells that are crucial to endurance. And two years ago, she began working with Nike engineers to design a marathon shoe. In Nike's Beaverton, Oregon, design lab, she ran on a specialized treadmill coupled with high-speed 3-D cameras that analyze foot strike, pressure and alignment. The result, the 6.8-ounce Zoom, is also available to mortals ($85).