Nosebands can restrict horses’ natural jaw movements, often preventing them from indicating discomfort when ridden. But whether this restraint method is stressful to horses has never been proven—until now.

In a recently released study, Australian researchers revealed that horses wearing nosebands show physiological signs of stress, which increase as noseband tightness increases. What’s more, they “rebound” from their physical restrictions as soon as those nosebands come off—suggesting that welfare has been compromised.

“The horse has a lot of information to give us about how we’re riding, but it has to be allowed to open its mouth to do so,” said Paul McGreevy, BVSc, PhD, MRCVS, MACVS (Animal Welfare), professor of animal behavior and animal welfare science at the University of Sydney.

“As a community of riders, we could be a lot more thoughtful about the price our horses pay when we prevent them from moving themselves in the way they would wish,” he said.

In their study, McGreevy and his fellow researchers evaluated 12 horses fitted with a double bridle and crank noseband (prior to the experiment none of the test horses had ever worn either piece of equipment), which are commonly used in elite dressage competitions, he said. They tested the horses with four different noseband settings: unfastened (loose); respecting the “two-finger” rule (two fingers can fit between the noseband and the horse’s nose); wide enough for a single finger to pass through; and adjusted so tight that no fingers can pass.

They found that as noseband tightness increased, so