As he does most years, Steve Waryan is preparing to compete in the Birkebeiner, the legendary 50-kilometer Nordic ski race in far northern Wisconsin. So you might think he’s skiing as much as he can. But no. He’s roller skiing, cycling, running, strength training, and completing HIIT (high-intensity interval training) workouts. And when he plays golf, he runs the hills of his local Minnesota course while carrying his clubs. “For me, it’s the ultimate cross-training,” he explains.