Over the past few years, the sport of running has been upended by a debate over shoe technology. It all began in early 2017, when Nike announced a prototype called the Vaporfly that was billed as improving a runner’s efficiency by 4 percent—a claim that was hard to believe until that spring, when Kenyan Eliud Kipchoge came seconds away completing a marathon in under two hours. The running community’s reaction was swift, with many claiming that the shoe wasn’t a breakthrough, it was a cheat. A lot has changed since then, with records at numerous distances being obliterated while other shoe brands look to duplicate the Vaporfly’s success, even as they call for new Nike prototypes to be banned. Today, even with the Olympics and other major athletic events postponed to prevent the spread of the coronavirus, the sport of running remains upside down, with the focus still on shoes instead of on who’s wearing them. Outside editor Chris Keyes speaks with our Sweat Science columnist, Alex Hutchinson, about how we got here and what it all means for the future of the sport.