McCutcheon L J, Geor R J
Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, USA.
Equine Vet J Suppl. 2010 Nov(38):135-41. doi: 10.1111/j.2042-3306.2010.00235.x.
There is evidence that extensive training in cool conditions results in improvements to heat dissipation that contribute to successful acclimatisation. In horses, the effects of a less extensive training regimen have not been determined.
This study investigated whether 10 consecutive days of moderate intensity treadmill training in cool conditions would improve thermoregulatory and sweating responses of horses to exercise in the heat.
Six unfit Thoroughbred horses completed a standardised treadmill exercise test (SET) in hot, dry conditions (32-34 °C, 45-55% RH) before (SET1) and after (SET2) 10 consecutive days of running at 55% VO2max for 60 min in cool conditions (19-21°C, 45-55% RH). Each SET consisted of a 5 min warm-up and cool down at a walk, 40 min of trotting (50% VO2max), 7 min at 75% VO2max and a 30 min standing recovery. Bodyweight was determined pre- and post SET. Heart rate, rectal, skin, pulmonary artery and muscle temperatures were measured throughout the SETs and sweating rate (SR) and sweat ion losses determined for each 5 min interval.
Following training, mean VO2max increased by 8.9% (P < 0.05). In SET2, PCV was lower during the last 30 min of exercise and end-exercise rectal, muscle and pulmonary artery temperatures were decreased by 1.5 ± 0.2, 0.8 ± 0.1 and 1.0 ± 0.2 °C, respectively (P < 0.05). Peak SR and the pattern of sweat ion losses during exercise was unchanged post training whereas SR and sweat losses during recovery were decreased (P < 0.05).
Similar SRs for a given core temperature during exercise but a more rapid decrease in recovery resulted in an overall reduction in sweat fluid losses with no change in sweat ion losses after training.
The results provide insight into the extent to which short-term training can improve the capacity of horses to exercise in hot conditions.
有证据表明，在凉爽环境中进行大量训练可改善散热情况，有助于成功实现适应性变化。对于马匹而言，训练强度较小的训练方案所产生的效果尚未明确。
本研究调查了在凉爽环境中连续10天进行中等强度跑步机训练是否会改善马匹在热环境中运动时的体温调节和出汗反应。
6匹体能不佳的纯种马在凉爽环境（19 - 21°C，相对湿度45 - 55%）中以最大摄氧量的55%连续跑60分钟，持续10天前后，于炎热干燥环境（32 - 34°C，相对湿度45 - 55%）下完成标准化跑步机运动测试（SET1和SET2）。每次SET包括5分钟的慢走热身和放松、40分钟的小跑（最大摄氧量的50%）、7分钟最大摄氧量75%的运动以及30分钟的站立恢复。在SET前后测定体重。在整个SET过程中测量心率、直肠温度、皮肤温度、肺动脉温度和肌肉温度，并确定每5分钟间隔的出汗率（SR）和汗液离子流失量。
训练后，平均最大摄氧量增加了8.9%（P < 0.05）。在SET2中，运动最后30分钟的红细胞压积较低，运动结束时直肠、肌肉和肺动脉温度分别降低了1.5±0.2、0.8±0.1和1.0±0.2°C（P < 0.05）。训练后运动期间的峰值出汗率和汗液离子流失模式未变，而恢复期间的出汗率和汗液流失量减少（P < 0.05）。
训练后，运动期间相同核心温度下出汗率相似，但恢复期间出汗率下降更快，导致汗液流失总量减少，而汗液离子流失量无变化。
这些结果为短期训练可在多大程度上提高马匹在炎热环境中运动的能力提供了见解。
