This better understanding of how rein tension affects horses through different equipment could help handlers improve their training skills and, thus, performance and welfare, said Marie Eisersiö, MSc, of the Faculty of Veterinary Medicine and Animal Husbandry at the Swedish University of Agricultural Sciences, in Uppsala.

Eisersiö and her team found horses respond faster and to lighter rein tension with a bitted bridle than with a halter—though they often fight the bit more. They also pay less attention to the handler when wearing a halter.

Horses have likely learned to associate bridles and halters with different experiences, including trying to pull the reins out of people’s hands to relieve their discomfort, she said.

“The bit is a sharper tool, and generally when people go to the store to get a more severe bit, it’s because they want more control of their horse,” Eisersiö said. “So that means the horse is being controlled through pain, basically, which is not okay.”

Horses can learn to respond to “softer” equipment, such as halters, she said. However, that requires better training and mastery of negative reinforcement—meaning the handler should know exactly when to release pressure.

Rein Tension Studies With Halters Versus Bits

Eisersiö and her colleagues worked with 20 riding school mares and geldings, ranging in age from 4 to 15. Using a rein tension meter, they measured how much backward force the horses accepted on the reins before backing up. The researchers tested each horse eight times with a flat-band (not a rope-knot) nylon halter and eight times in their usual bridle with a snaffle bit. They also observed the horses’ behavior.

They found the horses responded to less rein tension when they had a bit compared to the standard halter, Eisersiö said. This wasn’t surprising, she added, as most handlers would already expect this from personal experience.

However, they noted that with the bit, the horses tossed their heads and opened their mouths more, acting like they were trying to avoid the bit, she said. They even appeared to try to yank the reins away, probably based on previous experience. “All behaviors recorded during the rein tension signal phase likely reflect the horse’s understanding of what can lead to release of rein tension and/or its motivation/eagerness to get relief from rein tension,” she said.

When trained properly, horses should understand that their correct response to cueing is what leads to relief from tension, Eisersiö explained. However, in these riding school horses—as well as many other horses—relief often comes from conflict behavior that forces the handler to drop or loosen the reins. Ironically, that behavior briefly but significantly increases the tension.

“Bits can be painful, or at least create some discomfort for the horse,” she said. “In those cases it’s the discomfort that becomes the motivator to get the horse to do what’s been asked.”

Meanwhile, the horses were frequently less attentive when they wore the halter, she said. When they were paying attention, they responded to only slightly more rein tension than with a bit. Again, this could be based on horses’ past experiences. They “may have associated the halter with nontraining time and, thus, their attention was more on other things than on paying attention to rein tension signals,” Eisersiö stated in their study report, which appeared recently in Frontiers in Veterinary Science.

“We need to be aware of how much we affect our horses through our equipment,” she told The Horse. “Using bits or sharper tools might work because they’re more uncomfortable. But learning should be about communication between horse and rider, not how sharp the equipment is. When handlers apply learning theory and negative reinforcement correctly, softer equipment like halters can work very well.”

Bits Require Good Rider Training

The findings do not suggest people should not use bits, Eisersiö cautioned. Rather, bits should be recognized as a refined tool that requires the handler to be more aware of how to use them to avoid pain—including paying attention to rein tension.

And in fact, an earlier study by German researchers showed horses accepted an equal amount of rein tension when wearing bitted versus several kinds of bitless bridles, suggesting they find them equally aversive.

“Bits are not necessarily evil, and they shouldn’t be banned,” Eisersiö said. “But it’s important to train the hands that hold the reins.”

Eisersiö M, Byström A, Yngvesson J, Baragli P, Lanata A, Egenvall A. Rein Tension Signals Elicit Different Behavioral Responses When Comparing Bitted Bridle and Halter. Front Vet Sci. 2021;8:652015. Published 2021 May 7. doi:10.3389/fvets.2021.652015