“I’ve been small and weak my entire life—just, like, totally underdeveloped. I’ve always wondered what it would feel like to be big and strong.

“To be an elite marathoner with a body that’s light and lean: while you’re running, you feel amazing. You’re fluid and economical, floating along without having to carry a lot of muscle mass,” says Hall. “But the rest of the day, to be honest, is not a lot of fun. My energy was super low [throughout most of my career]. I took naps every day and felt pretty much useless when I wasn’t running.”

– Elite marathoner Ryan Hall (now retired)

Marathoner Ryan Hall says that even during his best years as a competitive athlete, he was “healthy” only in a narrowly defined way. As he put it, he was good at one thing: running. Everything else was rather laborious. Hall said he could be stirring pots of chili while making dinner and feel soreness in his shoulder the next day.

Not exactly the robust image that the running industry wants to promote.

The highest levels of performance come at the expense of health. In fact, I would say that the two are mutually exclusive,” says Mark Twight, former elite-level alpinist, competitive amateur cyclist, and professional trainer. When I spoke to him on the phone, Twight told me that the ideal physique for an athlete is defined by the singular task that athlete is trying to achieve. (Photographer Howard Schatz’s “Athlete” series offers a striking visual depiction of the range in athlete body types.) In the hyper-competitive and hyper-specialized world of professional sports, physical versatility is a common sacrifice. And it’s not just endurance sports.

“You can look at top level [male] cyclists, who always joke about having their wife or girlfriend carry the groceries, because they don’t have the upper body to do so,” says Twight. “But also, how healthy is the offensive lineman playing professional football, where it’s just size for the sake of size? That could certainly be considered ‘unhealthy’.”

Twight said that he was extremely light—around three percent body fat—while racing his road bike as a masters athlete around 2007. While this took a serious toll on bodily functions like testosterone levels and mood, he was faster than ever.