NEWS about stretching seems to come in waves. Stretch as part of your warm-up. No, stretch after your workout. No, don’t even bother stretching. Or the doozy: Even if you think you like it, it’s been oversold as a way to prevent injury or improve performance.

The truth is that after dozens of studies and years of debate, no one really knows whether stretching helps, harms, or does anything in particular for performance or injury rates. Yet most athletes remain convinced that stretching helps, and recently more and more have felt a sort of social pressure to show that they are limber, in part due to the popularity of yoga. Flexibility has become another area where many athletes want to excel.

They’re like one of my running partners, Claire Brown, a 35-year-old triathlete.

“I always feel like, well, athletes should do yoga,” Claire said. “It’s supposed to be really good for running, and when I do it regularly, it does loosen up my hips and make me feel better for running.”

Yet she puts off going to yoga.

“It shouldn’t feel like an obligation, but it always does,” Claire said. “The good classes are often an hour and a half long, and I’m thinking: ‘I could be running, I could be biking. But here I am, stretching and breathing.’