For Sera Wheeler, the Olympics is the reason for everything. It’s why she trains thirty hours a week, starves herself to under 100 pounds, and pops Advil like Tic Tacs. For her mother, Charlene, hungry for glory she never had, it’s why she rises before dawn to drive Sera to practice in a different state, and why the family scrimps, saves, and fractures. It’s why, when Sera’s best friend reports the gymnastics doctor to...