Talk to surgeons and speech language pathologists, and you quickly learn that there’s a whole universe of professionals at risk for vocal damage whose job descriptions, technically, do not emphasize the use of their voices at all. Like teachers, for instance. Also lawyers. And a growing number of group fitness instructors like Ms. Cohen.

Image Coco Cohen, a fitness instructor, developed vocal paralysis and had surgery on her vocal cords. Credit... via Coco Cohen

“This is a group that is so mindful of being healthy and taking care of their bodies, but their voices are really neglected,” said Leanne Goldberg, director of Grabscheid Voice and Swallowing Center at Mount Sinai Hospital in New York City.

Comprehensive data on this particular population is limited, but a small body of evidence suggests that fitness instructors are now among those at high risk. In 2016, Christine Estes, a speech language pathologist at the Weill Cornell Medicine Sean Parker Institute for the Voice, noticed that her patients featured a recurring cast of fitness instructors. She decided to conduct a study of them over a two-year period. What she discovered amazed her: They had polyps. They had nodules. They had hemorrhages. Real damage to the vocal cords that needed real treatment. All 24 were referred for behavioral treatment, and 10 opted to have surgery.

Instructors typically average around 15 classes per week, some starting as early as 5 a.m. Many lead several classes back-to-back, with almost no breaks in between. Throughout the day, they’re shouting directives — often while demonstrating the moves they’re describing — over loud, upbeat music and, in some cases, competing with the noise coming from treadmills, stationary bikes and clanging weights.

Most of all, they’re motivating their clients to push themselves, and that motivation generally takes the form of volume. And while most instructors do wear microphones, those devices may not help much if the studio has a low-quality sound system, or if the instructors don’t know how to use them to their vocal advantage. A result: Many instructors compromise their vocal health by giving what is a very taxing performance.