For more than a century, racehorse trainers have tied horses’ tongues to the front and side when they work or race. The purpose, trainers say, is to reduce breathing noises and help the horses perform better. But, until now, researchers have never confirmed that the tongue tie actually has a physical effect on the upper respiratory structures.

“My aim was to objectively assess if tongue ties contribute to upper airway stability,” said Heather J. Chalmers, DVM, Dipl. ACVR, assistant professor of radiology at the University of Guelph's Ontario Veterinary College in Ontario, Canada. “Based on my research, I think they do.”

Chalmers and colleagues investigated 12 Standardbred racehorses with and without tongue ties at a standstill. The team applied the tongue ties using a standard industry procedure, which involves pulling the tongue as forward as possible and tying it close to its base around the lower jaw with a nylon strap. The tongue is then pulled out to the side of the horse’s mouth. The horses did not appear uncomfortable during the procedure, Chalmers said.

Then the team took ultrasound images of five different regions of the upper respiratory tract, including the positions of several bones and cartilages responsible for supporting the upper airway, attaching the windpipe to the back of the throat, and joining the tongue to the skull. The team measured these structures' positions and their relationship to each other using an ultrasound technique that Chalmers developed in earlier work