Jones J H, Carlson G P
Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis 95616, USA.
Equine Vet J Suppl. 1995 Nov(20):23-30. doi: 10.1111/j.2042-3306.1995.tb05004.x.
The metabolic power required for sustained exercise in the horse is proportional to running speed. Moderately fast speeds require substantial energy expenditure and result in the generation of a massive metabolic heat load. Quantitative estimates of energy expenditure and heat production of horses at various running speeds were developed using empirically derived data from treadmill studies. Total metabolic power represents the sum of aerobic power indicated by the rate of oxygen consumption and net anaerobic power indicated by the rate of plasma lactate accumulation. These data were applied to typical running speeds and distances for each of the 4 phases of the endurance day of an Olympic level (CCI) 3-day-event to provide an estimate of the energy expenditure and heat production during each phase. In a given horse, the rates of energy expenditure and heat production are determined by running speed, while total energy expenditure and heat production are determined by a combination of running speed and duration of exercise at that intensity. The highest calculated rate of energy expenditure and heat production occurred during Phase B, the steeplechase, followed closely by Phase D, the cross-country course. Interestingly, the highest total energy expenditure and heat production occurred on Phase C, Roads and Tracks, which is usually considered a period for cool down and recovery between the relatively high speed steeplechase and the demanding cross-country course. Nevertheless, because the rate of energy expenditure is low during this phase, the horses would be expected to lose heat and lower body temperature during this interval. In hot and humid climates, dissipation of the exercise-induced heat load may be compromised, leading to a narrower range of safety between the rate of heat production and the ability of the horse to dissipate this heat to the environment. The results of this study could be used, should environmental conditions dictate, to provide quantitative guidelines as to how specific alterations of speed or distance of the various phases of the event would affect heat production.
马匹持续运动所需的代谢功率与奔跑速度成正比。适度较快的速度需要大量能量消耗，并导致产生巨大的代谢热负荷。利用跑步机研究的经验数据，得出了马匹在不同奔跑速度下的能量消耗和产热的定量估计值。总代谢功率代表由耗氧率指示的有氧功率与由血浆乳酸积累率指示的净无氧功率之和。这些数据应用于奥运会水平（CCI）三日赛耐力日四个阶段中每个阶段的典型奔跑速度和距离，以估算每个阶段的能量消耗和产热。对于某一匹特定的马，能量消耗率和产热率由奔跑速度决定，而总能量消耗和产热则由该强度下的奔跑速度和运动持续时间共同决定。计算得出的能量消耗率和产热率最高的阶段是B阶段，即障碍赛，紧随其后的是D阶段，即越野赛段。有趣的是，总能量消耗和产热最高出现在C阶段，即公路和跑道赛段，该阶段通常被认为是在相对高速的障碍赛和要求较高的越野赛之间的冷却和恢复阶段。然而，由于此阶段能量消耗率较低，预计马匹在此期间会散热并降低体温。在炎热潮湿的气候条件下，运动引起的热负荷的消散可能会受到影响，导致产热率与马匹向环境散热能力之间的安全范围变窄。如果环境条件需要，本研究结果可用于提供关于赛事各阶段速度或距离的特定改变将如何影响产热的定量指导。
