Effects of Cross-Adaptation and Aging on Heat Tolerance of Haenyeo during Passive Heating

Abstract

Korean haenyeo had been well-known for their unique adaptation to cold exposure, diving into cold sea water even in winter with wearing thin cotton-suit. Not onlycross-adaptationaleffect of cold exposure but also repetitive swimming could affect the heat tolerance of haenyeo despite the development of wetsuit. Heat tolerance induced by passive heat stress was examined through evaluating perspiratory and thermoregulatory responses. In a climate chamber where the air temperature was maintained at 28oC and the relative humidity at 50% RH, total 28 subjects (10 older haenyeos, 8 older females and 10 young females) immersed their leg under knees in 42oC hot tub for an hour. It was showed that haenyeos had the highest total sweat rate and maintained their sweat glands function. The heart rate was significantly lower than the other two groups and blood pressure was as low as young females. These results suggest that lifetime-cold exposure of haenyeos had affected their heat tolerance positively by cross-adaptational effect and underwater swimming reduced the effect of aging on cardiovascular health.