“I have really bad knees,” says Rebecca Ouding. “I have an old knee injury that gets aggravated,” says Bud Uyeda. “I ran a marathon 20 years ago, and after that, my arches collapsed,” says Dave Hafera ...

Like every fitness activity, running has its niches. Some people want to fight for first-place finishes, others cover wildly long distances in ultrarunning and cross country. For diehard minimalists, ...