Under his program athletes getting ready for 100-plus-mile ultra-marathons don’t run increasingly long distances until they hit their target; instead they train in 1-minute ultra bursts of activity followed by short cool downs. His routines bring a person up to the threshold of their VO2 max—the very point of exhaustion—and can transform a sprinter into an endurance athlete. The method is called high-intensity interval training, or HIIT, and breaks 50 years of running orthodoxy.
