The Scandinavian winter-swimming culture combines brief dips in cold water with hot sauna sessions, with conceivable effects on body temperature. We study thermogenic brown adipose tissue (BAT) in experienced winter-swimming men performing this activity 2–3 times per week. Our data suggest a lower thermal comfort state in the winter swimmers compared with controls, with a lower core temperature and absence of BAT activity. In response to cold, we observe greater increases in cold-induced thermogenesis and supraclavicular skin temperature in the winter swimmers, whereas BAT glucose uptake and muscle activity increase similarly to those of the controls. All subjects demonstrate nocturnal reduction in supraclavicular skin temperature, whereas a distinct peak occurs at 4:30–5:30 a.m. in the winter swimmers. Our data leverage understanding of BAT in adult human thermoregulation, suggest both heat and cold acclimation in winter swimmers, and propose winter swimming as a potential strategy for increasing energy expenditure.

斯堪的纳维亚冬季游泳文化结合了在冷水中短暂浸泡和热桑拿，对体温的影响是可以想象的。我们研究了经验丰富的冬季游泳男性每周进行 2-3 次这项活动的产热棕色脂肪组织 (BAT)。我们的数据表明，与对照组相比，冬季游泳者的热舒适状态较低，核心温度较低且缺乏 BAT 活动。为了应对寒冷，我们观察到冬季游泳者寒冷引起的产热和锁骨上皮肤温度的增加更大，而 BAT 葡萄糖摄取和肌肉活动的增加与对照组相似。所有受试者都表现出锁骨上皮肤温度的夜间降低，而冬季游泳者的明显峰值出现在凌晨 4:30-5:30。