Physiological Responses of Women during Exercise under Dry-Heat Condition in Winter and Summer.

Abstract

Fourteen young Japanese women were exposed to a dry-heat condition (Ta = 40 degrees C, rh = 30%) both in winter and summer. During an exposure for 110 min, they were rested on a bicycle ergometer for 20 min, exercised with an intensity of 40% Vo2 max for 60 min and recovery for 30 min. Their rectal and skin temperatures, and heart rate were determined every minute. Total sweat loss and dripping sweat were recorded throughout the experiment by independent bed balances which connected to a computer processor with an accuracy of 1 g. Sweat capsule with filter paper was used to measure sodium concentration on the forearm and back sites. Rectal temperature was not significantly different between winter and summer. Mean skin temperature was significantly higher in summer than in winter during exercise while heart rate was significantly lower in summer than in winter. Sweat evaporation and dripping in summer showed a tendency to increase much more than these in winter, but there were not significantly different. Sweat sodium concentration were significantly lower in summer than that in winter. It was found that sweating responses were not influenced by seasonal variation during exercise in dry-heat except the sweat sodium concentration.

Living in Western Australia induces some physiological adaptations of seasonal acclimatisation in the surgical burns team

“…The baseline, mean, and peak HR were lower in summer than winter, in the CON condition, which is consistent with research that reported a lower resting HR in summer than winter (by 5 bpm) in participants, in a thermoneutral climate chamber (25°C, 50% RH; [ 32 ]). Keatisuwan and colleagues (1996) similarly reported that the resting HR of participants following seasonal acclimatization was 9 bpm lower in summer than in winter [ 23 ], the same as the reduction in baseline HR that was noted in our study. The resting HR values in summer in the aforementioned studies were 74 bpm [ 32 ] and 71 bpm [ 23 ], whereas the mean, baseline HR value in summer in our study was 85 bpm.…”

“…Keatisuwan and colleagues (1996) similarly reported that the resting HR of participants following seasonal acclimatization was 9 bpm lower in summer than in winter [ 23 ], the same as the reduction in baseline HR that was noted in our study. The resting HR values in summer in the aforementioned studies were 74 bpm [ 32 ] and 71 bpm [ 23 ], whereas the mean, baseline HR value in summer in our study was 85 bpm. That could mean that the staff were simply fitter in summer, as regular exercise and physical activity can cause a reduction in resting HR [ 33 ].…”

“…While researchers have explored the influence that acclimation can have on occupational thermal strain [ 20 , 21 ], the potential for seasonal acclimatization has not been explored in depth in an occupational context, specifically one in which heat stress is a common occurrence. A lower resting T CORE and HR have been reported in summer compared to winter, in individuals living in in Korea [ 22 ] and Japan [ 23 ], respectively, where individuals experience differences in ambient temperatures between seasons. It is possible that staff working in heated OTs could benefit from acclimatization over the summer months in Western Australia where outdoor temperatures can exceed 40°C.…”

Current knowledge on the effects of humidity on physiological and psychological responses

“…Understanding the aforementioned criteria on body heat balance, the magnitude of heat stress in hot (warm) and humid environments has been studied, for example, by Niwa and Nakayama (1978), Smolander and Holmér (1991), Kondo et al (1996), Keatisuwan et al (1996), Maughan et al (2012), and Shen and Zhu (2015). In exercise physiology considering thermal environments, the primary purpose is supposed to be evaluation of changes in exercise capacity or performance in hot and humid environments, where Eskmax becomes minimal because heat loss from the human body is limited.…”

“…In exercise physiology considering thermal environments, the primary purpose is supposed to be evaluation of changes in exercise capacity or performance in hot and humid environments, where Eskmax becomes minimal because heat loss from the human body is limited. Under these specific situations, the magnitude of heat stress can be clearly estimated if individual and seasonal differences in sweating capacity (Keatisuwan et al, 1996) and heat acclimatization (Shen and Zhu, 2015) can be disregarded. In other words, accumulated knowledge on individual and seasonal differences in sweating capacity and heat acclimatization may depend on future studies to predict the magnitude of heat stress for various populations.…”