Oral Presentation 24th International Conference of Racing Analysts and Veterinarians 2026

Subchondral bone fatigue accumulated by Thoroughbred racehorses during training and racing and its association with musculoskeletal injury (130413)

Ashleigh V. Morrice-west 1 , Adelene S.M. Wong 1 , Euan Bennet 2 , Michael Pan 1 3 , William D. Height 1 , Cate Steel 4 , Brian Stewart 4 , Chris Whitton 1 , Peta L. Hitchens 1
  1. Equine Centre, University of Melbourne, Werribee, Vic, Australia
  2. School of Biodiversity, One Health and Veterinary Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland
  3. School of Mathematics and Statistics, University of Melbourne, Parkville , Vic, Australia
  4. Department of Veterinary Clinical Services, Hong Kong Jockey Club, Hong Kong

Racehorses are predisposed to musculoskeletal injuries (MSI) primarily due to accumulated bone fatigue from repeated skeletal loading during galloping. Subchondral bone fatigue accumulation has previously been estimated from racing data, however, the contribution of training workloads is unknown. We aimed to estimate the percentage subchondral bone fatigue life (%SBFL) accumulated during training and racing, and investigate their association with MSI, defined as lameness, injury or fracture from official veterinary records.

 

Training, racing and veterinary data for racehorses (n=5,215) at the Hong Kong Jockey Club from 2010-2021 were acquired. Published equations were used to estimate joint loads and %SBFL for slow-work, fast-work, barrier trials, and races, reported as medians (interquartile range; IQR). Rates were calculated as %SBFL over acute (14, 30, 60), intermediate (90, 120, 180) and chronic (365 day) windows. Cox proportional hazard models were generated to investigate the effects of %SBFL rates on time (days) to MSI.

 

Over the study period 59.3% (n=3,092) of horses sustained an injury. Accumulated %SBFL per event was highest for races (10.1%; IQR 9.07-11.12), followed by trials (8.19%; IQR 7.65-8.96), fast-work (3.21%; IQR 2.53-3.76), and slow-work (0.41%; IQR 0.41-0.47). However, fast-work contributed more cumulative %FL over preparations (39.6%; IQR 30.8-48.1) than slow-work (29.1%; IQR 23.6-39.2), races (17.8%; IQR 0.0-26.9), and trials (5.6%; IQR 0.0-10.7). Higher rates of %SBFL over all time windows were associated with greater risk of MSI (p<0.001; hazard ratios > 5 for the top 20th percentile of acute workload rates across all work-types).

 

Using our understanding of injury development to weight the impact of each workout on subchondral bone, we found training workloads contributed a substantial proportion of accumulated fatigue, and that fatigue accumulation rate is a key contributor to injury. Training workload data can therefore inform safer training practices and facilitate early identification of at-risk horses.