Using inertial measurement units (IMUs) placed on all four hooves, German and Dutch scientists have determined that breakover—the moment when the hoof’s position moves over the toe—lasts a shorter amount of time in certain gaits when the horse has wedges, rolled-toe shoes, or back-placed shoes compared to normal shoes. That should relieve pressure on the navicular bone and toe, which can be particularly beneficial for horses with pain in those areas, said Jenny Hagen, DrMedVet, of the Institute of Veterinary Anatomy, Histology, and Embryology in the Faculty of Veterinary Medicine at Leipzig University, in Germany.

“Our findings support the use of these therapeutic methods to ease breakover,” Hagen said.

IMUs on Each Hoof Detail Breakover Times in Different Shoes and Barefoot

Hagen and her fellow researchers equipped 10 sound Warmblood riding horses with IMUs attached by Velcro strips to the top of the front hooves and the sides of the back hooves (to keep them from getting hit by the horse’s front hooves during movement). They then measured how long it took for each foot to break over at walk and trot in different situations, in one of the first studies to investigate breakover in all four feet.

They found that a standard metal shoe caused breakover to take longer than if the horse were barefoot, she said.

A rolled-toe shoe or a palmarly placed (backward) shoe made up for that difference at the walk, however, by shortening breakover. The equipment didn’t improve the breakover rate compared to barefoot, but it helped bring it closer to the barefoot breakover rate. “Rolled-toe and palmarly placed shoes reduced the side effect of shoeing itself, which emphasizes the importance of these modifications to maintain soundness,” she said.

None of these factors affected breakover at the trot. However, when the researchers added a 5-degree wedge under the study horses’ heels, breakover was significantly shortened at both the walk and the trot.

“Heel elevation is associated with a steeper hoof angulation, causing reduced extension of the distal interphalangeal joint (DIPJ, or coffin joint) and an advantageous position of the hoof to break over,” said Hagen. “This effect is associated with less strain on the deep digital flexor tendon (DDFT) and decreased pressure on the navicular bone in the final part of the stance phase. Therefore, our study emphasizes the value of shoeing with heel wedges in the context of therapeutic shoeing related to these structures.”

They also found that regardless of the condition, breakover had a significantly different duration in the back feet than the front feet for each horse. In general, breakover in the back feet was shorter at the walk and longer at the trot compared to the front feet. “Overall, the findings suggest that fore and hind feet should be considered separately in analyses, but not left and right,” Hagen said.

On Average, Regular Trims Show No Change in Breakover Time

The team noted that, contrary to certain beliefs, regular trims didn’t change average breakover time. That might be because the study horses’ regularly scheduled trimming every seven to nine weeks didn’t lead to a big enough difference in hoof angle, Hagen explained. In their study, the average difference in hoof angle after trimming was less than 1 degree.

On an individual scale, however, some horses might benefit more from regular trimming than others. And those that have not been trimmed for several months or more might have a better breakover time after trimming. But the researchers did not investigate that in this study.

“A lot of people think that if you just trim the hoof, it should be faster on breakover,” Hagen said. “That might be true for some horses, but not for all horses in general.”

The study, “Influence of trimming, hoof angle and shoeing on breakover duration in sound horses examined with hoof-mounted inertial sensors,” was published in August 2021 in Veterinary Record.