The impact of cumulative bone fatigue on musculoskeletal injury risk in racing Thoroughbreds.
Authors: Morrice-West Ashleigh V, Wong Adelene S M, Hitchens Peta L, Whitton R Chris
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary Musculoskeletal injuries in racing Thoroughbreds accumulate through repetitive loading rather than occurring as acute events, yet quantifying this skeletal fatigue has historically been difficult. Morrice-West and colleagues analysed stride data from wearable technology collected across 3,168 race starts by 405 Tasmanian Thoroughbreds to calculate cumulative bone fatigue loads, then used survival analysis to determine how fatigue accumulation rates over different timeframes (single start, four-start windows, and full career) influenced injury risk. Higher bone fatigue accumulation rates significantly elevated musculoskeletal injury risk, with the most striking finding that horses with either very low (<0.25) or very high (≥0.75) workloads over the preceding four starts faced substantially greater hazard—2.89-fold and 8.51-fold respectively—compared to horses maintaining medium workloads (0.25–0.75). For equine practitioners, these findings suggest wearable technology monitoring offers a practical pathway to identify at-risk horses before injury manifests clinically, allowing timely intervention through individualised workload adjustment rather than continuing with either insufficient or excessive training intensity.
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Practical Takeaways
- •Use wearable stride-tracking technology to monitor cumulative skeletal fatigue and identify horses at elevated injury risk before lameness occurs
- •Maintain moderate, consistent workload rates over 4-start preparation windows (0.25-0.75 range); avoid both extreme underwork and overwork as both increase injury risk
- •Establish individual fatigue baselines during each horse's career and modify training intensity when fatigue accumulation rates rise, rather than waiting for clinical signs of injury
Key Findings
- •Horses with higher bone fatigue accumulation over a single start had 3.37-fold greater MSI risk (p=0.048)
- •Career-long bone fatigue rate was strongly associated with MSI risk (HR 1.80; p<0.001)
- •Intermediate workloads (0.25-0.75 over four starts) resulted in 1027-day survival time to MSI, compared to 760 days for low workloads and 405 days for high workloads
- •Both extremely low (<0.25) and very high (≥0.75) workload rates over four-start windows significantly increased MSI risk compared to medium workloads