More than once, Ms. Kostal has made the mistake of taking conference calls from bed. She has one client in Britain, which puts her on calls in the middle of the night in San Francisco. She recalled recently falling asleep during a call and being awakened by her own snoring.

“The sound quality of those calls is so poor, I don’t think anyone noticed,” she said. But she has stopped taking conference calls while supine. “That was a real wake-up call to start paying better attention.”

And in conference calls, no one knows you’re in the downward-dog position. One 52-year-old financial consultant in Manhattan said she spent the time during conference calls working her way through her daily yoga regimen. Like several other people interviewed for this article, she did not want her name used. “The image of my butt in the air isn’t exactly what I want to put out there as my professional persona,” she said.

Aware of the danger of distraction, some people request that conference calls be conducted via video. “You can tell if people are distracted from a person’s tone,” said Jason Reece, a web developer in Atlanta. “People are more likely to be engaged when the camera is on. It inspires a person to be sitting up and paying attention.”

Mr. Reece asks his clients to use videoconferencing. He says there are always people who will resist, telling him their Internet connection is too weak, for example. Giving them the benefit of the doubt, he asks that they put up a still photo. “Even if you only get a photo, it’s more humanizing,” he said.

Art Schoeller, vice president and principal analyst at Forrester Research, said it was common for people on video calls to choose the voice-only option. “That does allow for the yoga scenario,” he said.

Mr. Schoeller added that while he had seen some companies require videoconferencing to encourage a higher degree of attentiveness, the conversion from audio to video has remained slow. “Video is on a long, slow curve of more expansive adoption,” he said, “but the industry has long struggled with how to accelerate it.”