On a ripe June morning at the base of Stratton Mountain in Vermont, Jessie Diggins is squatting down in the dirt and lifting a volleyball-size boulder to her chest. Then the power-packed 5-foot-4-inch Olympic cross country skier suddenly springs up and heaves the rock high into the air like a shot put. No one marks the distance of her throw. No fans are there cheering her on. Diggins is simply grinding...

I took my first strides as a hockey player at Minnehaha Arena, an old-school ice rink in Minneapolis known for its punishing cold temperature and sweeping barrel-truss roof. My dad was right there beside me, his outstretched hands both a lifeline and a parental spatula. After every fall, every flailing wipeout, he would flip me back over and scrape me off the ice. Then he’d dust me off, take my hand, and we’d start all over again...