Horses topped out at 29% of their body weight in a study that evaluated gait changes when loaded. | Photo: Anne M. Eberhardt/The Horse

By measuring gait symmetry—the evenness of a horse’s left steps to its right during various gaits—scientists are able to gather significant information about loading, or the weight horses can carry on their backs. Gaits that get sufficiently out of sync, they say, are a strong indicator of how much is too much.

“We showed a widely applicable and welfare-friendly method to evaluate loading capacity of horses by gait analysis using an accelerometer,” said Akihiro Matsuura, PhD, lecturer in the department of animal science at the Kitasato University School of Veterinary Medicine in Aomori. Scientific analysis of the accelerometer readings revealed certain “peaks” that could be defined as the symmetry of the gait, he added.

Matsuura colleagues from Kitasato University and the Towada Riding Club, studied Japanese horses at the walk and trot. The six study mares—relatively small Hokkaido native horses—averaged 14.1 hands in height and 340 kilograms (750 pounds) in weight. They were ridden by the same 66-kilogram (145-pound) rider in all tests, but researchers loaded the horses progressively with more and more weights, with a maximum of 130 kilograms (287 pounds) total weight. Researchers evaluated the horses with an accelerometer as they moved in a straight line at predetermined, fixed speeds