Gordon Kyle, Blondin Denis P, Friesen Brian J, Tingelstad Hans Christian, Kenny Glen P, Haman François
Faculty of Health Sciences, University of Ottawa , Ottawa , Canada.
Faculty of Medicine, Department of Biochemistry, Microbiology and Immunology, Ottawa , Canada.
J Appl Physiol (1985). 2019 Jun 1;126(6):1598-1606. doi: 10.1152/japplphysiol.01133.2018. Epub 2019 Mar 21.
Daily compensable cold exposure in humans reduces shivering by ~20% without changing total heat production, partly by increasing brown adipose tissue thermogenic capacity and activity. Although acclimation and acclimatization studies have long suggested that daily reductions in core temperature are essential to elicit significant metabolic changes in response to repeated cold exposure, this has never directly been demonstrated. The aim of the present study is to determine whether daily cold-water immersion, resulting in a significant fall in core temperature, can further reduce shivering intensity during mild acute cold exposure. Seven men underwent 1 h of daily cold-water immersion (14°C) for seven consecutive days. Immediately before and following the acclimation protocol, participants underwent a mild cold exposure using a novel skin temperature clamping cold exposure protocol to elicit the same thermogenic rate between trials. Metabolic heat production, shivering intensity, muscle recruitment pattern, and thermal sensation were measured throughout these experimental sessions. Uncompensable cold acclimation reduced total shivering intensity by 36% ( = 0.003), without affecting whole body heat production, double what was previously shown from a 4-wk mild acclimation. This implies that nonshivering thermogenesis increased to supplement the reduction in the thermogenic contribution of shivering. As fuel selection did not change following the 7-day cold acclimation, we suggest that the nonshivering mechanism recruited must rely on a similar fuel mixture to produce this heat. The more significant reductions in shivering intensity compared with a longer mild cold acclimation suggest important differential metabolic responses, resulting from an uncompensable compared with compensable cold acclimation. Several decades of research have been dedicated to reducing the presence of shivering during cold exposure. The present study aims to determine whether as little as seven consecutive days of cold-water immersion is sufficient to reduce shivering and increase nonshivering thermogenesis. We provide evidence that whole body nonshivering thermogenesis can be increased to offset a reduction in shivering activity to maintain endogenous heat production. This demonstrates that short, but intense cold stimulation can elicit rapid metabolic changes in humans, thereby improving our comfort and ability to perform various motor tasks in the cold. Further research is required to determine the nonshivering processes that are upregulated within this short time period.
人类每日可补偿性冷暴露可使颤抖减少约20%，而不改变总产热，部分原因是增加了棕色脂肪组织的产热能力和活性。尽管长期以来，适应和驯化研究表明，每日核心体温的降低对于引发对反复冷暴露的显著代谢变化至关重要，但这从未得到直接证实。本研究的目的是确定每日冷水浸泡导致核心体温显著下降是否能在轻度急性冷暴露期间进一步降低颤抖强度。七名男性连续七天每天进行1小时的冷水浸泡（14°C）。在适应方案之前和之后，参与者使用一种新颖的皮肤温度钳制冷暴露方案进行轻度冷暴露，以使各试验之间的产热率相同。在这些实验过程中测量了代谢产热、颤抖强度、肌肉募集模式和热感觉。不可补偿性冷适应使总颤抖强度降低了36%（ = 0.003），而不影响全身产热，是之前4周轻度适应所显示效果的两倍。这意味着非颤抖产热增加以补充颤抖产热贡献的减少。由于7天冷适应后燃料选择没有变化，我们认为所募集的非颤抖机制必须依赖类似的燃料混合物来产生这种热量。与更长时间的轻度冷适应相比，颤抖强度的更显著降低表明了不可补偿性与可补偿性冷适应所产生的重要代谢差异反应。几十年来的研究一直致力于减少冷暴露期间颤抖的出现。本研究旨在确定连续七天的冷水浸泡是否足以减少颤抖并增加非颤抖产热。我们提供的证据表明，全身非颤抖产热可以增加，以抵消颤抖活动的减少，从而维持内源性产热。这表明短暂但强烈的冷刺激可以在人类中引发快速的代谢变化，从而提高我们在寒冷中的舒适度和执行各种运动任务的能力。需要进一步研究来确定在这个短时间内上调的非颤抖过程。
