From starting and stopping to turning and galloping, the repetitive movements of polo ponies place demands on their muscoluskeletal system that could predispose them to injury and lameness. Researchers recently determined that, compared with performance horses in other disciplines, polo ponies display a high degree of movement asymmetry, though this doesn’t always mean the animal is lame or in pain.
To take a closer look at this movement asymmetry, Thilo Pfau, PhD, a senior lecturer in bio-engineering at The Royal Veterinary College in the United Kingdom, evaluated 60 polo horses using inertial measurement units (IMUs) and compared the results to two established thresholds for movement symmetry. The current thresholds are based on slightly different approaches.
“One commonly used and cited threshold is 3 mm asymmetry for pelvic movement and 6 mm asymmetry for head movement,” he explained.
The other system, which Pfau used in his study, results in slightly higher asymmetry values. “The threshold for pelvic movement in our system is more like a 4 to 5 mm threshold and for head movement it’s more like 8 to 9 mm, but we accounted for the difference,” he said.
The team placed IMUs on each horse’s poll and between the tubera sacrale, the highest point of the hipbone on either side of the croup.
Of the horses studied, 60% to 67% of horses fell outside threshold limits for symmetrical movement. Pfau stressed, however, that, “very importantly, asymmetry in movement is not always caused by pain, which would then be clearly a lameness.”
Conformational issues could be a contributing factor to movement asymmetry, which, Pfau said, is a bit of a “chicken and egg” scenario: “Do differences in conformation cause movement symmetry, or do changes in movement and hence force, between limbs, lead to long-term changes in conformation?”
Further, long-term studies are needed to find out how many of the horses that move asymmetrically are suffering from pain-related lameness, he said. Currently, Pfau is collaborating with researchers from Uppsala University, in Sweden, on a study on racehorses investigating the sources of these asymmetries and how they relate to training regimens.
The study, “Movement asymmetry in working polo ponies,” will appear in an upcoming issue of the Equine Veterinary Journal.