Turf track surface interaction with speed and musculoskeletal injury risk in Thoroughbred racehorses.

Abstract

BACKGROUND: Injury modelling based on changes in speed and stride characteristics of racehorses has become a primary industry focus for the Thoroughbred racing industry. However, speed and stride characteristics are strongly associated with track condition; therefore, reliable quantification of surface variables for use in future models is imperative. OBJECTIVES: This study aimed to understand the interaction of objective turf track condition score (TCS) measurement with racing speed and injury in flat racing Thoroughbred horses. STUDY DESIGN: Retrospective time series analysis. METHODS: Race-day data from 16 flat racing seasons (2008/9-2023/24, n&#x2009;=&#x2009;40,824 races) were used to compare monthly TCS (based on penetrometer measurements), the coefficient of variability (CV) for TCS, race speed (over the final 600&#x2009;m) and the number of race starts. Injury data from 7 seasons (2015-17, 2019-24) were used to calculate the monthly incidence rate (IR per 1000 race starts) of musculoskeletal injury (MSI). A mixed effects linear model was used to assess the relationship between speed, TCS, race distance and horse rating. RESULTS: Race starts (n&#x2009;=&#x2009;437,506), TCS and speed showed strong seasonal fluctuations, with more starts, lower and more variable TCS (4, IQR 3-5, CV&#x2009;=&#x2009;0.44) and higher race speed (16.7&#x2009;m/s, IQR 16.1-17.2) in summer compared with winter (TCS 10, IQR 8-10, CV&#x2009;=&#x2009;0.22, p&#x2009;<&#x2009;0.001 and speed 15.1&#x2009;m/s, IQR 14.3-15.8, p&#x2009;<&#x2009;0.001). Race speed had a strong negative quadratic relationship with TCS (&#x3b2;&#x2082;&#x2009;=&#x2009;-0.03, p&#x2009;<&#x2009;0.001), a negative linear correlation with race distance and was positively correlated with horse rating. There were 433 MSI (IR&#x2009;=&#x2009;2.22, 95% CI 2.20-2.44), with an immediate (0 lag time) positive association with seasonal changes in TCS (r&#x2009;=&#x2009;-0.28). MAIN LIMITATIONS: Low monthly numbers of MSI constrained analysis of interaction with track variables. CONCLUSIONS: TCS provides a reliable quantitative measure of track condition which could be used to refine future models of injury risk in racing Thoroughbreds.