Marlin D J, Scott C M, Schroter R C, Mills P C, Harris R C, Harris P A, Orme C E, Roberts C A, Marr C M, Dyson S J, Barrelet F
Centre for Equine Studies, Animal Health Trust, Newmarket, Suffolk, UK.
Equine Vet J Suppl. 1996 Jul(22):70-84.
The aim of the present study was to determine the effect of different environmental conditions on physiological response to exercise. Four winter acclimatised, nonheat acclimated horses of different breeds were exercised at 20 degrees C/40% RH (CD), 30 degrees C/40% RH (HD) and 30 degrees C/80% RH (HH). The exercise test was designed to represent the structure and intensity of a One star Speed and Endurance test (competition exercise test [CET]). All 4 horses were able to complete the full CET (60 min + 30 min active recovery) in CD and HD, but only one horse completed the CET in HH. Two horses were stopped because of pronounced general fatigue and one because of a right atrial temperature (TRA) of 43 degrees C. Oxygen uptake on each phase was not different between CD and HD, but was higher during Phases B, C and D in HH. Mean peak TRA at the end of Phase D was 40.3 +/- 0.2, 41.6 +/- 0.4 and 42 +/- 0.3 degrees C for CD, HD and HH, respectively. Corresponding, mean peak rectal temperatures (TREC) following Phase D were 39.5 +/- 0.1, 40.6 +/- 0.1 and 41.5 +/- 0.1 degree C for CD, HD and HH, respectively. Mean time to peak TREC was 9.3 +/- 1.1 (CD), 7.3 +/- 1.8 (HD) and 10.8 +/- 2.3 (HH) min and was not significantly different between conditions (P > 0.05). Heat dissipation amounted to 83 +/- 1, 73 +/- 2 and 70 +/- 1% of heat production in CD, HD and HH, respectively. Weight loss was significantly correlated with both body surface area (CD r = 0.85; HD r = 0.87; HH r = 0.81) and bodyweight (CD r = 0.97; HD r = 0.93; HH r = 0.94). The greatest weight loss recorded was 4.6% bodyweight in one horse in HD. The mean increase in exercise intensity over the whole CET (in terms of VO2) of HD and HH and HH compared with CD was 5 +/- 3 and 14 +/- 3% higher, respectively. The exercise induced hyperthermia and the reduced capacity for heat dissipation produced partial compensatory responses in minute ventilation (VE), particularly during Phase C, when the horses were trotting. In HD, the increase in VE was achieved mainly through an increase in frequency, whilst in HH it was achieved through an increase in tidal volume (VT). The horses demonstrated a high degree of tolerance to environmental heat load, suggesting a high thermoregulatory capacity. However, for unacclimatised animals exercising in severely hot and humid conditions, performance may be limited.
本研究的目的是确定不同环境条件对运动生理反应的影响。选用四匹经过冬季驯化、未经过热适应的不同品种马匹，分别在20摄氏度/40%相对湿度（CD）、30摄氏度/40%相对湿度（HD）和30摄氏度/80%相对湿度（HH）条件下进行运动。运动测试旨在模拟一星速度耐力测试（竞赛运动测试[CET]）的结构和强度。所有四匹马在CD和HD条件下都能够完成完整的CET（60分钟+30分钟主动恢复），但在HH条件下只有一匹马完成了CET。两匹马因明显的全身疲劳而停止运动，一匹马因右心房温度（TRA）达到43摄氏度而停止运动。CD和HD阶段各阶段的摄氧量没有差异，但HH阶段的B、C和D阶段摄氧量更高。D阶段结束时，CD、HD和HH的平均峰值TRA分别为40.3±0.2、41.6±0.4和42±0.3摄氏度。相应地，D阶段后的平均峰值直肠温度（TREC），CD、HD和HH分别为39.5±0.1、40.6±0.1和41.5±0.1摄氏度。达到峰值TREC的平均时间分别为9.3±1.1（CD）、7.3±1.8（HD）和10.8±2.3（HH）分钟，不同条件之间无显著差异（P>0.05）。散热分别占CD、HD和HH产热的83±1%、73±2%和70±1%。体重减轻与体表面积（CD r = 0.85；HD r = 0.87；HH r = 0.81）和体重（CD r = 0.97；HD r = 0.93；HH r = 0.94）均显著相关。记录到的最大体重减轻是HD一匹马体重的4.6%。与CD相比，HD和HH在整个CET期间（以VO2计）运动强度平均增加分别高5±3%和14±3%。运动引起的体温过高和散热能力下降在分钟通气量（VE）上产生了部分代偿反应，特别是在C阶段马匹小跑时。在HD中，VE增加主要通过频率增加实现，而在HH中则通过潮气量（VT）增加实现。马匹对环境热负荷表现出高度耐受性，表明其具有较高的体温调节能力。然而，对于在酷热潮湿条件下运动的未适应动物，其表现可能会受到限制。
