Automatic hoof-on and -off detection in horses using hoof-mounted inertial measurement unit sensors

For gait classification, hoof-on and hoof-off events are fundamental locomotion characteristics of interest. These events can be measured with inertial measurement units (IMUs) which measure the acceleration and angular velocity in three directions. The aim of this study was to present two algorithms for automatic detection of hoof-events from the acceleration and angular velocity signals measured by hoof-mounted IMUs in walk and trot on a hard surface. Seven Warmblood horses were equipped with two wireless IMUs, which were attached to the lateral wall of the right front (RF) and hind (RH) hooves. Horses were walked and trotted on a lead over a force plate for internal validation. The agreement between the algorithms for the acceleration and angular velocity signals with the force plate was evaluated by Bland Altman analysis and linear mixed model analysis. These analyses were performed for both hoof-on and hoof-off detection and for both algorithms separately. For the hoof-on detection, the angular velocity algorithm was the most accurate with an accuracy between 2.39 and 12.22 ms and a precision of around 13.80 ms, depending on gait and hoof. For hoof-off detection, the acceleration algorithm was the most accurate with an accuracy of 3.20 ms and precision of 6.39 ms, independent of gait and hoof. These algorithms look highly promising for gait classification purposes although the applicability of these algorithms should be investigated under different circumstances, such as different surfaces and different hoof trimming conditions

Biomechanical findings in horses showing asymmetrical vertical excursions of the withers at walk

The walk and trot are inherently symmetrical gaits, making them potentially suitable for the detection of left-right asymmetries. The aims of this study were to describe asymmetrical vertical excursions of the withers at walk in non-lame high-level dressage horses and to seek associations between these asymmetric movements and other kinematic variables and vertical ground reaction forces (vGRFs). Seven dressage horses, judged clinically as being sound, walked unridden and unrestrained on a treadmill with an integrated force measuring system (480 Hz), from which spatiotemporal and vGRF variables were extracted. Markers were tracked by 12 infrared cameras (240 Hz). The vertical position of the sixth thoracic vertebra (T6), limb protraction and retraction distances throughout stance, and global limb lengths were determined. Contralateral trial-mean differences were calculated, including difference in T6 minimum vertical position between contralateral steps (T6minDiff). Mixed models were used to study associations between symmetry parameters. Trial-mean T6minDiff ranged between 0.3–23 mm. Of the seven horses, five consistently dropped the withers more in early left forelimb stance, one was fairly symmetrical, and one dropped the withers more in early right forelimb stance. Comparisons between contralateral limbs showed the following associations. The forelimb that was retracted when T6min was lowest showed greater retraction at toe-off (1 mm increase predicted 0.17 mm T6minDiff increase) and shorter stance duration (1 ms decrease predicted 0.3 mm T6minDiff increase). The hind limb that was in midstance when T6min was lowest showed a greater range of motion during the stance phase (1 mm increase in protraction or retraction predicted 0.2 mm T6minDiff increase). The haunches were displaced away from the side of the forelimb that was protracted when T6min was lowest (1 mm lateral shift predicted 0.07 mm T6minDiff increase). Forelimb and hind limb vGRF parameters were non-significant. Asymmetry of vertical withers movement in horses assessed as being sound at trot was related to a complex pattern of asymmetries in spatiotemporal variables throughout the stride cycle rather than to vertical load redistribution between the forelimbs. This suggests that the asymmetry may be due to inherent laterality rather than weight-bearing lameness

Biomechanical findings in horses showing asymmetrical vertical excursions of the withers at walk

The walk and trot are inherently symmetrical gaits, making them potentially suitable for the detection of left-right asymmetries. The aims of this study were to describe asymmetrical vertical excursions of the withers at walk in non-lame high-level dressage horses and to seek associations between these asymmetric movements and other kinematic variables and vertical ground reaction forces (vGRFs). Seven dressage horses, judged clinically as being sound, walked unridden and unrestrained on a treadmill with an integrated force measuring system (480 Hz), from which spatiotemporal and vGRF variables were extracted. Markers were tracked by 12 infrared cameras (240 Hz). The vertical position of the sixth thoracic vertebra (T6), limb protraction and retraction distances throughout stance, and global limb lengths were determined. Contralateral trial-mean differences were calculated, including difference in T6 minimum vertical position between contralateral steps (T6minDiff). Mixed models were used to study associations between symmetry parameters. Trial-mean T6minDiff ranged between 0.3–23 mm. Of the seven horses, five consistently dropped the withers more in early left forelimb stance, one was fairly symmetrical, and one dropped the withers more in early right forelimb stance. Comparisons between contralateral limbs showed the following associations. The forelimb that was retracted when T6min was lowest showed greater retraction at toe-off (1 mm increase predicted 0.17 mm T6minDiff increase) and shorter stance duration (1 ms decrease predicted 0.3 mm T6minDiff increase). The hind limb that was in midstance when T6min was lowest showed a greater range of motion during the stance phase (1 mm increase in protraction or retraction predicted 0.2 mm T6minDiff increase). The haunches were displaced away from the side of the forelimb that was protracted when T6min was lowest (1 mm lateral shift predicted 0.07 mm T6minDiff increase). Forelimb and hind limb vGRF parameters were non-significant. Asymmetry of vertical withers movement in horses assessed as being sound at trot was related to a complex pattern of asymmetries in spatiotemporal variables throughout the stride cycle rather than to vertical load redistribution between the forelimbs. This suggests that the asymmetry may be due to inherent laterality rather than weight-bearing lameness

Automatic hoof-on and -off detection in horses using hoof-mounted inertial measurement unit sensors

For gait classification, hoof-on and hoof-off events are fundamental locomotion characteristics of interest. These events can be measured with inertial measurement units (IMUs) which measure the acceleration and angular velocity in three directions. The aim of this study was to present two algorithms for automatic detection of hoof-events from the acceleration and angular velocity signals measured by hoof-mounted IMUs in walk and trot on a hard surface. Seven Warmblood horses were equipped with two wireless IMUs, which were attached to the lateral wall of the right front (RF) and hind (RH) hooves. Horses were walked and trotted on a lead over a force plate for internal validation. The agreement between the algorithms for the acceleration and angular velocity signals with the force plate was evaluated by Bland Altman analysis and linear mixed model analysis. These analyses were performed for both hoof-on and hoof-off detection and for both algorithms separately. For the hoof-on detection, the angular velocity algorithm was the most accurate with an accuracy between 2.39 and 12.22 ms and a precision of around 13.80 ms, depending on gait and hoof. For hoof-off detection, the acceleration algorithm was the most accurate with an accuracy of 3.20 ms and precision of 6.39 ms, independent of gait and hoof. These algorithms look highly promising for gait classification purposes although the applicability of these algorithms should be investigated under different circumstances, such as different surfaces and different hoof trimming conditions