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Biomechanical Findings in Horses Showing Asymmetrical Vertical excursions of the Withers at Walk

Penelitian - Researchers shows the existence of consistent and repetitive vertical movement asymmetry of the forehand during walking in high-level dressage horses. Asymmetrical vertical motion of the forehand was systematically associated with contralateral differences, but not with differences in vertical ground reaction forces.

The walk and trot are inherently symmetrical gaits, which makes them potentially suitable for the detection of left-right asymmetries in spatiotemporal and ground reaction force (GRF) variables. Detection of such asymmetries is relevant both in veterinary medicine and in equestrian sports, especially dressage.

Penelitian Biomechanical Findings in Horses Showing Asymmetrical Vertical excursions of the Withers at Walk

Lameness is typically associated with kinematic asymmetries that result in redistribution of vertical ground reaction forces (vGRF) from the lame limb to the compensating limbs. The trot is the preferred gait for lameness detection, because the presence of a suspension phase results in higher vGRF compared to the walk. Peak vGRF and vertical impulse are the most reliable indicators of weight bearing lameness.

Although the gait is regarded as being less important for lameness diagnosis, the walk is of great importance in a number of equestrian disciplines. This is exemplified by the fact that all current international dressage tests award a double coefficient for the quality of both collected walk and extended walk.

Symmetry and regularity are important criteria for judging overall gait quality and hence for dressage performance. Horses exhibiting irregularity in the walk may even be eliminated from competitions and, consequently, be presented for clinical work up. This warrants the study of asymmetries in the walk of non-lame dressage horses.

With the increasing availability of equipment capable of accurate quantification of equine gait, the measurement of even subtle asymmetries has become possible. However, this poses new problems for the interpretation of the data since asymmetry and lameness are not interchangeable terms.

No living being is perfectly symmetrical, locomotor asymmetries may be the result of non-pathological conditions such as cerebral laterality, which is manifested as a motor dominance of the left/right side of the body. This type of sidedness is known to be present in many animal species and may be associated with low level kinematic and GRF asymmetries.

Motor laterality in horses has, for example, been studied in terms of preferred canter leads, kinematic asymmetries in the gait of young Standardbred trotters and a preference for grazing or halting with one forelimb in a more advanced position.

Sound horses exhibit left-right asymmetries in axial moments around the fore hooves when walking on straight lines and on circles and these have been interpreted as manifestations of sidedness. Several studies have focused on non-pathological sources of asymmetry at trot, in which the vertical excursions of head, withers and/or pelvis are commonly used for symmetry evaluation.

Withers symmetry has been shown to be the most direct indication of asymmetry in the forelimbs that is least prone to confounding influences. However, the walk has been largely neglected and relatively little is known about inherent asymmetries in this gait.

“Our objective was to determine the amount of asymmetry of the vertical excursions of the withers, in a group of non-lame high-level dressage horses walking freely on a treadmill,” said Anna Byström of the Swedish University of Agricultural Sciences and team.

This was performed using kinematic and kinetic data from an earlier study. For any systematic and consistent asymmetry pattern that was identifiable at group level, mixed-models were used to determine which asymmetries in vGRFs, and/or inter-limb timing, and/or limb kinematics that best predicted the asymmetric withers movement at the walk.

“We used an approach that involved plotting graphs and performing mixed-effects modelling on data from stride- and trial-level and aimed at obtaining stable results from the models that were congruent with conclusions drawn from graphical representations of raw and descriptive data,” said Byström and team said.

Journal : Anna Byström et al. Biomechanical findings in horses showing asymmetrical vertical excursions of the withers at walk, PLOS ONE, September 27, 2018, DOI:10.1371/journal.pone.0204548



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