Pre-exercise cooling may help Thoroughbreds in hot training: full analysis

A new study suggests that cooling Thoroughbreds before warmup in hot conditions could help preserve hydration status and limit heat buildup without hurting performance. Researchers at the Japan Racing Association’s Equine Research Institute tested six trained Thoroughbreds in a randomized crossover design and found that a 10-minute shower before exercise reduced body weight loss and lowered pulmonary artery temperature compared with a 30-minute walking pre-treatment, while run time to exhaustion did not change. (jstage.jst.go.jp)

The work arrives as heat stress remains a growing welfare and performance issue across equine sport. A recent literature review described heat stress as a serious concern not only in racing and elite competition, but also in leisure riding, transport, and general management under hot, humid conditions. That review also emphasized that prompt recognition of heat stress and effective cooling methods, including cool water and airflow, are important for horse welfare. (link.springer.com)

In the new paper, horses underwent three pre-exercise conditions in a hot room with a wet-bulb globe temperature of 32.5 ± 0.5°C: 30 minutes of treadmill walking at 1.7 m/sec, 30 minutes of standing rest, or a 10-minute shower at 26.2 ± 0.8°C. After that, all horses completed a brief warmup and then a high-intensity treadmill bout at roughly 115% of VO2max until exhaustion. The shower treatment significantly reduced post-exercise body weight loss versus both walking and rest, and pulmonary artery temperature was lower than in the walking group after pre-treatment, warmup, and main exercise. Heart rate, plasma lactate, rectal temperature, and run time did not differ significantly, suggesting the cooling intervention improved thermal and fluid-related measures without blunting performance. (jstage.jst.go.jp)

That distinction matters because warmup is usually meant to prepare horses physiologically for work, but in hot environments it can also add thermal strain before the main effort begins. The authors specifically noted that walking in a hot environment before exercise is not recommended for preventing exertional heat illness because it raises body temperature, and they suggested that a short, moderate-intensity warmup after pre-cooling may be sufficient. (jstage.jst.go.jp)

While direct outside commentary on this specific paper was limited, the findings fit with broader expert guidance from equestrian bodies and prior research. FEI heat-preparedness materials emphasize acclimatization, access to water and ice, cooling stations, shade, ventilation, and familiarity with cold-water cooling protocols at events. EquiManagement’s own recent reporting has also highlighted that horses training or competing in hot climates may benefit from targeted heat-mitigation strategies, including acclimatization and cooling interventions. (inside.fei.org)

Why it matters: For equine veterinarians, trainers, and support teams, this study offers a practical pre-exercise management option that may reduce sweat-related weight loss and internal heat load in hot climates without compromising short-duration performance. That could be especially relevant for racetrack settings, high-intensity training sessions, and events where horses face repeated exposure to thermal stress. It also reinforces a broader clinical point: heat-risk management shouldn’t begin only after exercise ends. Pre-exercise planning, acclimatization, hydration oversight, and cooling logistics may all shape outcomes before a horse ever enters the main workload. (jstage.jst.go.jp)

There are still limits to keep in mind. This was a small study involving six trained Thoroughbreds under controlled conditions, so field performance in different breeds, disciplines, climates, and competition formats still needs study. Even so, the signal is clinically useful: if pre-cooling can lower thermal strain without reducing output, it may become a more common part of hot-weather protocols. (jstage.jst.go.jp)

What to watch: The next step will be whether larger field studies, racing authorities, and sport governing bodies translate pre-cooling evidence into formal hot-weather recommendations for training and competition management. (inside.fei.org)