The effects of water on limb and upper-body kinematics in horses walking and trotting in a water track.

Abstract

Rehabilitation after a musculoskeletal injury has become an essential part of veterinary care. Various forms of exercise in water have been described as an effective medium to improve function while preventing further injuries. This study evaluated kinematic changes of horses walking and trotting on a water track (WTr) versus overground (OG). Eleven horses, equipped with IMU sensors (EquiMoves®; attached to the cannon bones of each leg, the head, withers, back (T15), tuber sacral and L/R tuber coxae) were measured at walk and trot overground (OG1), while going through a water track (85m long; water height 33cm), and once more overground (OG2). Linear mixed models were used to compare the different conditions (p <0.05). There was no significant difference in symmetry of head, withers and sacrum at walk. At trot, symmetry index of head, withers and sacrum decreased (-45.7%, -41.7% and -41.2%) in the WTr. Speed was significantly lower under WTr conditions compared with OG conditions at walk. At trot, speeds were similar. At walk and trot in the WTr, there was a significant increased stride duration (+14.9% and +15.6%), swing duration of both FLs (+19.1% and +38.5%) and HLs (+19.2% and +19.1%), and stance duration of both FLs (+13.5% and +7.9%) and HLs (+11.6% and +10%). Stride length increased only at trot in the WTr (+11.7%). At walk, FL pro- and retraction decreased (-14.2% and -16.2%) and HL protraction increased (+48.4%). At trot, pro- and retraction of only the HLs increased (+68.4% and +20.8%). No differences between OG1 and OG2 were found. The main conclusion of this study is that there is a combined effect of gait and water on upper-body symmetry, limb sagittal angles and stride timings, where increased hindlimb pro- and retraction yielded the most considerable change compared to overground locomotion. The reduced speed in water at walk, should be considered as a confounding factor. Since speeds were not different between conditions at trot, these effects seem to have been caused by the water. This information can help clinicians to meet individual rehabilitation requirements. Nevertheless, more studies are required to determine the long-term effects of WTr exercise.