Comparison Between Inertial Sensor and Video-Based Detection of Spatiotemporal Limb Movement Parameters During Equine...

Equine swimming is increasingly used for injury prevention and rehabilitation, but objective analysis of movement during swimming remains limited compared to land-based locomotion. Spatiotemporal parameters are essential for evaluating therapeutic outcomes, yet capturing these parameters is technically challenging due to difficulties in observing limb motion in water. Inertial sensors, already widely applied in equine science, offer a promising solution for measuring swimming kinematics objectively. The objective of this study was to evaluate the reliability of inertial sensors placed on equine distal limbs in detecting key spatiotemporal events during swimming by comparing it with video-based detection made by veterinarians. For the duration of the hindlimb swimming cycle, 24 data values were analysed and showed an "excellent" agreement, with an intraclass correlation coefficient = 0.96, 95% CI: 0.904-0.983, and Bland-Altmann analysis showed an upper limit of agreement of 50 ms (95% CI: 70 ms, 30 ms) and lower one of -60 ms (95% CI: -40 ms, -80 ms). The estimates of the "swimming" duty factor of the hindlimb (n = 24) demonstrated "moderate" to "excellent" with intraclass correlation of 0.82 (95% CI: 0.625-0.920) and limits of agreement of 4.39% (95% CI: 6.21%, 2.53%) and -5.28% (95% CI: -3.42%, -7.14%). The results of the forelimb were mixed, suggesting that the cycle duration and "swimming" duty factor parameters determined for this limb should be used with caution. Overall, the findings confirm that inertial sensors, particularly on the hindlimbs, provide reliable spatiotemporal measurements and are well suited for studying equine swimming.