Validation of Distal Limb Mounted Imu Sensors for Stride Detection and Locomotor Quantification in Warmblood Horses at Walk and Trot

Abstract

Reasons for performing study: IMU-sensor based techniques arebecoming more popular in horses as a tool for objective locomotorassessment. Using currently proposed methods only limited informationabout stride variables can be obtained for walk and trot.Objectives: To describe, evaluate and validate a method of stridedetection and quantification (i.e. hoof-on/off detection and stanceduration calculation) at walk and trot using distal limb mounted IMU-sensors.Study design: Validation study.Methods: To compare IMU-sensors and motion capture (MoCap) withforce plate data as the gold standard, 7 warmblood horses equippedwith metacarpal/metatarsal IMU-sensors (range: low-g accelerometer16 g; high-g accelerometer 200 g) and reflective markers for MoCapwere hand walked and trotted over a force plate. All instruments wereframe synchronised and data were collec ted at 200 Hz. Using fourcustom-built algorithms hoof-on/off timing over the force plate andstance duration were calculated for each trial from the IMU data.Accuracy of the computed parameters was calculated as the meandifference in milliseco nds between the IMU/MoCap generated data andthe data from the force plate (bias) and precision as the standarddeviation of these differences.Results: The best performing IMU algorithm achieved for stanceduration at walk an accuracy, precision and percentage of error of28.5 ms/31.6 ms/3.7% for the forelimbs and 5.5 ms/20.1 ms/2.2% forthe hindlimbs respectively. At trot the best performing algorithmachieved an accuracy, precision and percentage of error of 27.6 ms/8.8 ms/8.4% for the forelimbs and 6.3 ms/33.5 ms/9.1% for thehindlimbs. Using IMU algorithms for hoof-off detection a better overallaccuracy and precision was obtained, than when using MoCap.Conclusions: The observed IMU validation performance appears verypromising, and seems ready to practically and accurately determineimportant stride variables at walk and also at trot, being the key gait forlameness assessment and training evaluation.Ethical animal research: This study was approved by the local ethicscommittee. Horses were owned by the University. Sources of funding:This study was funded by STW Valorisation Grant 13448. Competinginterests: None declared.