Jessica Diggins’s 30 kilometres cross country silver medal on Sunday is even more remarkable because the American suffered from food poisoning the previous day. Diggins skied on her own behind Norwegian winner Therese Johaug for two-thirds of the race in brutal conditions to claim her biggest individual career success. Silver in the longest race came after bronze in the shortest, the sprint, earlier in the Beijing Games, her first individual medals after a team sprint gold in 2018. That in itself was impressive enough as Diggins said: “To have a medal in the sprint and the 30km are the ultimat…