Faculty of Health and Sport Sciences, University of Tsukuba , Ibaraki , Japan.
Department of Health Sciences, Prefectural University of Hiroshima , Hiroshima , Japan.
Am J Physiol Regul Integr Comp Physiol. 2019 May 1;316(5):R535-R542. doi: 10.1152/ajpregu.00203.2018. Epub 2019 Feb 13.
Hypothermia can occur during aquatic exercise despite production of significant amounts of heat by the active muscles. Because the characteristics of human thermoregulatory responses to cold during exercise have not been fully elucidated, we investigated the effect of low-intensity exercise on the shivering response to core cooling in cool water. Eight healthy young men (24 ± 3 yr) were cooled through cool water immersion while resting (rest trial) and during loadless pedaling on a water cycle ergometer (exercise trial). Before the cooling, body temperature was elevated by hot water immersion to clearly detect a core temperature at which shivering initiates. Throughout the cooling period, mean skin temperature remained around the water temperature (25°C) in both trials, whereas esophageal temperature (T) did not differ between the trials ( > 0.05). The T at which oxygen uptake (V̇o) rapidly increased, an index of the core temperature threshold for shivering, was lower during exercise than rest (36.2 ± 0.4°C vs. 36.5 ± 0.4°C, < 0.05). The sensitivity of the shivering response, as indicated by the slope of the T-V̇o relation, did not differ between the trials (-441.3 ±177.4 ml·min·°C vs. -411.8 ± 268.1 ml·min·°C, > 0.05). The thermal sensation response to core cooling, assessed from the slope and intercept of the regression line relating T and thermal sensation, did not differ between the trials ( > 0.05). These results suggest that the core temperature threshold for shivering is delayed during low-intensity exercise in cool water compared with rest although shivering sensitivity is unaffected.
尽管活跃的肌肉会产生大量热量，但在水中运动时仍可能会出现体温过低的情况。由于人类在运动中对寒冷的体温调节反应的特征尚未完全阐明，我们研究了低强度运动对在冷水中核心冷却时颤抖反应的影响。八名健康的年轻男性（24±3 岁）在休息时（休息试验）和在水上自行车测功计上进行无负荷蹬踏时（运动试验）通过冷水浸泡进行冷却。在冷却之前，通过热水浸泡将体温升高，以清楚地检测到开始颤抖的核心温度。在整个冷却期间，平均皮肤温度在两个试验中均保持在水温（25°C）附近，而食管温度（T）在两个试验中没有差异（>0.05）。耗氧量（V̇o）快速增加的 T 值，即颤抖的核心温度阈值的指标，在运动时低于休息时（36.2±0.4°C 比 36.5±0.4°C，<0.05）。颤抖反应的敏感性，如 T-V̇o 关系的斜率所示，在两个试验中没有差异（-441.3±177.4 ml·min·°C 比-411.8±268.1 ml·min·°C，>0.05）。从 T 和热感觉之间回归直线的斜率和截距评估核心冷却的热感觉反应，在两个试验中没有差异（>0.05）。这些结果表明，与休息相比，在冷水中进行低强度运动时，颤抖的核心温度阈值会延迟，尽管颤抖的敏感性不受影响。
