CORTINA d’AMPEZZO, Italy — In the little resort town of Stratton, Vermont, the pine trees are green, the summers are quiet, and the cross-country ski community is tight. It’s there that Jessie Diggins, the most decorated American Olympian in her sport, trains in the late spring through the fall. It was there, in August, that Diggins rode a stationary bike while a group of elite cross-country racers worked out around her.
