Exercise heat acclimation (HA) is known to magnify the sweating response by virtue of a lower threshold as well as increased gain and maximal capacity of sweating. However, HA has been shown to potentiate the shivering response in a cold-air environment. We investigated whether HA would alter heat loss and heat production responses during water immersion. Twelve healthy male participants underwent a 10-day HA protocol comprising daily 90-min controlled-hyperthermia (target rectal temperature, Tre 38.5 °C) exercise sessions. Preceding and following HA, the participants performed a maximal exercise test in thermoneutral conditions (ambient temperature 23 °C, relative humidity 50%) and were, following exercise, immersed in 28 °C water for 60 min. Thermal comfort zone (TCZ) was also assessed with participants regulating the temperature of a water-perfused suit during heating and cooling. Baseline pre-immersion Tre was similar pre- and post-HA (pre: 38.33 ± 0.33 °C vs post: 38.12 ± 0.36 °C, p = 0.092). The Tre cooling rate was identical pre-to post-HA (-0.03 ± 0.01 °C·min-1, p = 0.31), as was the vasomotor response reflected in the forearm-fingertip temperature difference. Shivering thresholds (p = 0.43) and gains (p = 0.61) were not affected by HA. TCZ was established at similar temperatures, with the magnitude in regulated water temperature being 7.6 (16.3) °C pre-HA and 5.1 (24.7) °C post-HA (p = 0.65). The present findings suggest that heat production and heat loss responses during whole body cooling as well as the skin thermal comfort zone remained unaltered by a controlled-hyperthermia HA protocol.

中文翻译：

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热适应不会改变对核心冷却和皮肤热舒适区的自主反应

众所周知，运动热适应 (HA) 可以通过较低的阈值以及增加的出汗量和最大出汗量来放大出汗反应。然而，HA 已被证明可以增强冷空气环境中的颤抖反应。我们研究了 HA 是否会改变浸水过程中的热损失和产热反应。12 名健康男性参与者接受了为期 10 天的 HA 方案，包括每天 90 分钟的受控热疗（目标直肠温度，Tre 38.5 °C）锻炼课程。在 HA 前后，参与者在热中性条件（环境温度 23 °C，相对湿度 50%）下进行了最大运动测试，并在运动后浸入 28 °C 水中 60 分钟。还评估了热舒适区 (TCZ)，参与者在加热和冷却过程中调节水灌注套装的温度。基线预浸 Tre 与 HA 前后相似（前：38.33 ± 0.33 °C 与后：38.12 ± 0.36 °C，p = 0.092）。Tre 冷却速率与 HA 前后相同（-0.03 ± 0.01 °C·min-1，p = 0.31），正如反映在前臂-指尖温度差异中的血管舒缩反应一样。颤抖阈值 (p = 0.43) 和增益 (p = 0.61) 不受 HA 的影响。TCZ 是在相似的温度下建立的，调节水温的幅度为 HA 前 7.6 (16.3) °C 和 HA 后 5.1 (24.7) °C（p = 0.65）。