Wyndham C H, Rogers G G, Senay L C, Mitchell D
J Appl Physiol. 1976 May;40(5):779-85. doi: 10.1152/jappl.1976.40.5.779.
Four trained young men worked for 4 h/day at 40-50% of their maximum aerobic capacity first for 3 days at 25 degrees C db, 18 degrees C wb, and then for 10 consecutive days at 45 degrees C db, 32 degrees C wb. This portion of the study was mainly concerned with central circulatory changes during acclimatization. The central circulatory adaptation to work in heat could be divided into four distinct phases: phase I (day 1) was characterized by a progressive fall in stroke volume (SV) during heat exposure but cardiac output (CO) was maintained above control values by high heart rates. Phase II (days 2 and 3) was marked by increases in SV ande decreases in heart rate but with little change in CO from phase I. During phase III (days 4-8 of acclimatization), CO increased due to increases in SV. Phase IV (days 6-8) was associated with decreases in rectal and skin temperature towards control levels. SV and HR both decline in this phase so that CO was not elevated greatly above control levels. The results indicated that central circulatory and temperature regulating events are not casually associated in acclimatization.
四名经过训练的年轻男性每天以其最大有氧能力的40%-50%工作4小时，首先在25℃干球温度、18℃湿球温度下工作3天，然后在45℃干球温度、32℃湿球温度下连续工作10天。该研究的这一部分主要关注适应过程中的中枢循环变化。中枢循环对热环境下工作的适应可分为四个不同阶段：第一阶段（第1天）的特征是热暴露期间每搏输出量（SV）逐渐下降，但心输出量（CO）通过高心率维持在对照值以上。第二阶段（第2天和第3天）的特点是SV增加、心率下降，但与第一阶段相比CO变化不大。在第三阶段（适应的第4-8天），由于SV增加，CO升高。第四阶段（第6-8天）与直肠温度和皮肤温度降至对照水平有关。此阶段SV和HR均下降，因此CO没有比对照水平大幅升高。结果表明，在适应过程中，中枢循环和体温调节事件并非偶然相关。
