Giesbrecht G G, Bristow G K
Laboratory for Exercise and Environmental Medicine, Health, Leisure and Human Performance Research Institute, Faulty of Physical Education and Recreation Studies, Manitoba, Canada.
Aviat Space Environ Med. 1998 Jan;69(1):17-22.
Following cold water immersion, the post-cooling decrease in esophageal temperature (Tes) (i.e., afterdrop) is 3 times greater during exercise than during shivering, presumably due to increased muscular blood flow and convective core-to-periphery heat loss with exercise (J. Appl. Physiol. 63:2375, 1987). We felt that if exercise were to commence once the afterdrop period during shivering is complete, the threat of a further decrease in Tes (i.e., a second afterdrop) during the subsequent exercise would be minimized because much of the convective capacity for core cooling would already be dissipated.
Six subjects were each cooled three times in 8 degrees C water, until Tes decreased to 35.3 +/- 0.7 degrees C, and rewarmed by either shivering alone, exercise, or exercise commencing once a shivering afterdrop period was complete.
The initial afterdrop was greater during Exercise only (1.1 +/- 0.4 degrees C) than Shivering only (0.35 +/- 0.3 degrees C) and Shivering-Exercise (0.45 +/- 0.2 degrees C) (p < 0.05). In contrast, exercise caused a secondary afterdrop of only 0.38 +/- 0.3 degrees C during Shivering-Exercise (p < 0.05). The initial rewarming rate during Exercise only (3.45 degrees C.h-1) was greater than the initial (2.7 degrees C.h-1) and second (2.4 degrees C.h-1) rewarming rates during Shivering-Exercise (p < 0.05), but not significantly greater than during Shivering only (2.99 degrees C.h-1) (p < 0.1).
It is likely that during the Shivering-Exercise protocol, continued blood flow to shivering muscles: a) contributes to the initial afterdrop, and thus b) diminishes the convective capacity (or heat sink) available for further cooling during subsequent exercise.
冷水浸泡后，运动期间食管温度（Tes）的降温后下降（即体温过低）比寒颤时大3倍，这可能是由于运动时肌肉血流量增加以及核心到外周的对流热损失增加（《应用生理学杂志》63:2375，1987）。我们认为，如果在寒颤后的体温过低期结束后开始运动，那么在随后的运动中Tes进一步下降（即二次体温过低）的风险将降至最低，因为核心降温的大部分对流能力已经消散。
6名受试者在8摄氏度的水中各接受3次冷却，直到Tes降至35.3±0.7摄氏度，然后分别通过单独寒颤、运动或在寒颤后的体温过低期结束后开始运动进行复温。
仅运动时的初始体温过低（1.1±0.4摄氏度）大于仅寒颤时（0.35±0.3摄氏度）和寒颤 - 运动时（0.45±0.2摄氏度）（p<0.05）。相比之下，在寒颤 - 运动期间，运动仅导致0.38±0.3摄氏度的二次体温过低（p<0.05）。仅运动时的初始复温速率（3.45摄氏度·小时⁻¹）大于寒颤 - 运动时的初始复温速率（2.7摄氏度·小时⁻¹）和二次复温速率（2.4摄氏度·小时⁻¹）（p<0.05），但并不显著大于仅寒颤时的复温速率（2.99摄氏度·小时⁻¹）（p<0.1）。
在寒颤 - 运动方案中，持续流向寒颤肌肉的血液可能：a）导致初始体温过低，因此b）减少了后续运动期间可用于进一步冷却的对流能力（或热阱）。
