Lindinger M I, Geor R J, Ecker G L, McCutcheon L J
School of Human Biology, University of Guelph, Ontario, Canada.
Equine Vet J Suppl. 1995 Nov(20):133-9. doi: 10.1111/j.2042-3306.1995.tb05019.x.
We studied the effects of heat and relative humidity (RH) on plasma volume (PV) and ion responses to submaximal exercise and 60 min recovery in Thoroughbreds. Five horses were exercised at 50% of peak VO2 in cool, dry (CD, T = 22 degrees C, RH = 45-55%), and hot, humid (HH, T = 30-34 degrees C, RH = 80-85%) conditions until a pulmonary artery temperature of 41.5 degrees C was reached. Blood was obtained from the carotid artery. Body mass was measured at rest and after 30 min of recovery. The thermal conditions had no effect on the PV and ion responses during exercise and initial 30 min of recovery. Exercise resulted in an 8.5% decrease in PV within the first 2 min and, in the absence of changes in plasma [Na+] and [Cl-], was responsible for a 150 to 185 mmol decrease in plasma Na+ and Cl- contents. The decrease in PV was responsible for about 50% of the increase in packed cell volume (37% at rest; 51% at 2 min of exercise). Plasma [K+] and K+ content increased rapidly during the first 2 min of exercise. With cessation of exercise, plasma [K+] declined with a half time of about 2 min; recovery of PV and plasma Na+ and Cl- contents occurred with a half time of 10-15 min, with nearly complete recovery by 30 min. In the HD trial, between 30 and 60 min of recovery there were further decreases in PV and ion contents. It is concluded that with this exercise protocol, thermal stress had minimal influence on the rate and magnitude of exercise-induced changes in PV and ion contents. However, thermal stress during recovery from exercise may impede the restoration of PV and ion contents.
我们研究了热环境和相对湿度（RH）对纯种马血浆容量（PV）以及次最大运动和60分钟恢复过程中离子反应的影响。五匹马在凉爽干燥（CD，温度T = 22摄氏度，相对湿度RH = 45 - 55%）和炎热潮湿（HH，温度T = 30 - 34摄氏度，相对湿度RH = 80 - 85%）条件下，以峰值摄氧量（VO2）的50%进行运动，直至肺动脉温度达到41.5摄氏度。从颈动脉采集血液。在休息时和恢复30分钟后测量体重。热环境对运动期间及恢复最初30分钟的PV和离子反应没有影响。运动在最初2分钟内导致PV下降8.5%，且在血浆[Na +]和[Cl -]无变化的情况下，致使血浆Na +和Cl -含量减少150至185 mmol。PV的下降约占红细胞压积增加量的50%（休息时为37%；运动2分钟时为51%）。运动最初2分钟内血浆[K +]和K +含量迅速增加。运动停止后，血浆[K +]以约2分钟的半衰期下降；PV以及血浆Na +和Cl -含量以10 - 15分钟的半衰期恢复，到30分钟时几乎完全恢复。在HH试验中，恢复30至60分钟期间，PV和离子含量进一步下降。得出的结论是，按照此运动方案，热应激对运动诱导的PV和离子含量变化的速率和幅度影响极小。然而，运动恢复期间的热应激可能会阻碍PV和离子含量的恢复。
