Accuracy of G irth Based Measurements of Stride Characteristics in Horses Trotting on a Treadmill

This study aimed to investigate the possibility of obtaining the beginning and end of stance from a girth‐mounted I nertial M easurement U nit ( IMU ), by comparing data from the IMU with data from an opto‐electronic system. Methods 15 horses were trotted on a treadmill, with markers on hooves and a G irth M arker ( GM ) on a wireless IMU over the sternum. Proreflex cameras collected 3D marker data. T‐tests and Intraclass Correlation Coefficients ( ICC s) were used to decipher any difference between diagonally paired limbs; GM and hoof markers; and GM and IMU , the limits of agreement of which were also assessed using a Bland Altman method. Results Timings of diagonally‐coupled limbs were not significantly different at beginning (P = 0.77 and 0.95), or end of stance (P = 0.60 and 0.46) for right or left diagonal respectively. The diagonal in stance was identifiable from GM y position, with which IMU derived position had 97%, and IMU roll 100% agreement. Stance according to hoof markers did not differ significantly from GM z acceleration at beginning (P = 0.49 ± 0.01, P = 0.92 ± 0.007), or GM z velocity at end (P = 0.84 ± 0.007, P = 0.83 ± 0.007), in right or left diagonal respectively. A strong correlation was seen between beginning and end of stance according to GM and IMU events (each R 2 >0.99). Relationships between IMU and GM amplitudes were less convincing, with a significant difference at peak acceleration (P<0.05, Standard Deviation = 2.70 m/s/s, ULOA  = 5.93, LLOA  = −4.66). Conclusions A girth‐based IMU can identify temporal stride characteristics in trot on a treadmill, but inferences from amplitude data should be treated with caution until further investigated. Ethical Animal Research Approved by Hartpury College Research Ethics Committee. Sources of funding:  Research self‐funded by the first author. Competing interests:  none.