Field-training in young two-year-old thoroughbreds: investigating cardiorespiratory adaptations and the presence of exercise induced pulmonary hemorrhage.
Authors: Massie Shannon, Bayly Warwick, Ohmura Hajime, Takahashi Yuji, Mukai Kazutaka, Léguillette Renaud
Journal: BMC veterinary research
Summary
# Editorial Summary: Cardiorespiratory Adaptations in Young Thoroughbreds During Early Training Over a 12-week introductory training programme including weekly speed work, ten two-year-old Thoroughbreds demonstrated substantial improvements in aerobic capacity and ventilatory efficiency, with peak oxygen consumption increasing by 28% and ventilatory equivalent dropping from 26 to 23 ml/kg/min—indicating their lungs were extracting oxygen more effectively from each breath taken. Researchers measured these adaptations using validated ergospirometry facemasks during 600-metre high-speed exercise tests at weeks 4 and 12, alongside post-exercise sampling of blood lactate, ammonia and hematocrit levels, with endoscopic examination to screen for exercise-induced pulmonary haemorrhage (EIPH). Whilst maximal heart rate and heart rate at maximum speed both increased significantly, the primary driver of improved ventilation was an elevation in respiratory frequency rather than deeper breathing, and the horses showed a measurable shift towards greater anaerobic contribution to energy production (from 15.6% to 18.5%)—a pattern expected as conditioning progresses. Reassuringly, none of the cohort exhibited endoscopic signs of EIPH, suggesting that well-managed introductory training programmes at this age need not precipitate pulmonary bleeding. These findings support structured, progressive conditioning for young racehorses and provide baseline data for practitioners monitoring respiratory adaptation, though field professionals should recognise that individual variation and training intensity remain important variables in longer-term management.
Read the full abstract on PubMed
Practical Takeaways
- •Young Thoroughbreds (20-23 months) show robust cardiorespiratory adaptations to properly structured introductory training without developing EIPH, supporting safety of early training protocols
- •Training-induced improvements in ventilatory efficiency and aerobic capacity indicate young horses are physiologically capable of tolerating field training with weekly speed work
- •Absence of EIPH in young horses despite high-speed exercise suggests age may be a protective factor or current training methods are appropriate for this age group
Key Findings
- •Peak oxygen consumption increased 28% following 12 weeks of introductory training in young Thoroughbreds (P<0.001)
- •Ventilatory efficiency improved with training, shown by decreased ventilatory equivalent of oxygen (26±3.6 to 23±3.7; P=0.02)
- •Anaerobic contribution to energy production increased from 15.6±6.1% to 18.5±6.3% with training (P=0.02)
- •No tracheobronchoscopic evidence of exercise-induced pulmonary hemorrhage was detected in any of the 10 young horses despite high-speed exercise testing