A few days before competing in the Engadin Marathon in Switzerland last March, Ben Sim stood atop a snow-covered hill in Germany. Sim, an Australian, was about to find out whether he could make the jump from cross-country skiing to nordic combined. Literally. Observing were Finn Marsland, the coach of the Australian cross-country ski team, and Fabian Mauz, a German coach who had assisted some Australian athletes at the Junior World Championships in the Black...