The Utility and Reliability of Treadmill Tests for Monitoring Thoroughbreds in Training.

Abstract: This study evaluated the reliability of five treadmill protocols that assess heart rate (HR) and blood lactate (Bla) responses in Thoroughbred horses to determine their effectiveness in serving as potential tools for monitoring fitness and the wellbeing of racehorses. Of the five exercise tests, four consisted of repeated interval gallops at constant speeds (8 m/s and 10 m/s) and grade (6°) and one test of a continuous gallop at constant speeds (8 m/s) and grade (6°). Eight hundred and twenty-three gallops in total were performed by 64 horses. The test-retest reliability and absolute agreement between treadmill tests were assessed using Intraclass correlation coefficient (ICC) with a two-way mixed-effect model. Statistical significance was set at < 0.05. Overall, the mean of the mean HR for each of the five test gallops was 203 ± 11.3 bpm. The mean HR ICC of the five tests of 0.756 indicates good reliability of the tests, as HRs during each gallop were consistent between tests. Protocol comparison showed that all protocols have good reliability with gallops 1 and 5 scoring highest (0.79: 0.81) and gallop 4 lowest at 0.621. The recovery mean HR ICC for 30 s, 60 s, 90 s and 120 s recovery were 0.421, 0.504, 0.595 and 0.571 respectively. Overall, the data suggests that gallop HR is the more reliable variable with recovery HRR reliability improving to an acceptable level at 60 s and 90 s recovery. Together, the treadmill tests demonstrated acceptable reliability to measure both gallop HR and HHR responses, whereas BLa responses were less consistent.