Whether your horse takes several short, quick trot steps into the canter or jumps right into that rocking-horse gait, the moment when his legs change sequence probably seems fleeting. To a group of researchers from Michigan State University (MSU) though, that moment of change is of great interest.
In their recent study, the researchers found that the moment when horses switch between the trot and the canter results in a brief loss of stability and coordination, which appears to happen just after a change in the angle of the horses’ joints.
Researchers observed four Miniature Horses moving from the trot to the canter using infrared cameras that photographed 34 reflective tape markers placed on different parts of the horses’ bodies. The horses, without being given cues about when to pick up the canter, were led by a human who increased speed gradually, and the researchers analyzed the angles and ranges of motion captured on film.
The team observed that the joints closest to the center of the horse's body—the hip and the shoulder—showed an increase in variability of their angles, meaning that the legs were swinging farther forward and farther back during the transition than they did at a normal trot. The angles returned to the expected range once the transition to canter was complete.
The researchers concluded that the hip joint of the trailing hind limb showed the most variability just before the transition, perhaps indicating how critical the hip is to gaits like the canter, in which the legs do not move in pairs. The hip is responsible not only for the movement of the joints below it but also the pelvis and the spine, which could be especially critical to the canter. This hip likely initiates the transition from trot to canter, a transition that takes about two-and-a-half strides to complete, the team said.
But why study locomotion so intensely?
“Gaits and gait changes are fundamental to locomotion,” said study author Hilary Clayton, BVMS, PhD, MRCVS, Dipl. ACVSMR. “Scientists are interested in the mechanics of the gaits themselves and how these differ among species with different conformations, bipeds, quadrupeds, etc. The trigger factor for gait changes is a source of much controversy but the actual mechanics of gait changes have received relatively little research attention.”
Clayton, the Mary Anne McPhail Dressage Chair in Equine Sports Medicine at MSU, doubts that the changes in joint angle noted during the switch from trot to canter have much connection to injury risk. The horses were using their joints in those instances the way they were intended to be used—as springboards into a new gait.
While the horses used in the experiment were considerably smaller than the average riding horse, Clayton said there’s no reason to suspect that the sequence or timing of their leg movements would differ from their larger relatives.
But one area she said merits more research is how the added weight and balance of a rider might affect a horse’s gait transitions.
“That's the sort of information that will be useful to trainers,” she said. “For example, if the initiation of the transition is different depending on whether the horse is on its forehand or more collected. I don't know the answer to that question yet.”
That next step in exploring this phenomenon will require significantly more infrared cameras (the ones in this study cost $15,000 each, Clayton said) to capture an adequate number of strides using a larger horse.
The study, "Spatio-temporal gait characteristics during transitions from trot to canter in horses," was published in Zoology (Jena).
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