"This is the hardest conditioning drill for me," Rutten says. "It's very good for explosive power." When Rutten is at his fittest, he runs on the treadmill for 10 minutes at 11 m.p.h. Then, he does a quick static stretch before beginning sprints. Here's how: Turn the incline on your treadmill as high as it goes, then sprint at a sustained 9mph for 45 seconds. Rest for 30 seconds, and then begin your second rep of 10. "The 45 seconds seem to go very slow, and then the rest seems fast," Rutten laughs. "You just have to keep going – the 9mph part just comes." Unless you're an anaerobic beast, you'll need to build up to that level first. But it's intense no matter where you start.