Physiological responses and manual performance in humans following repeated exposure to severe cold at night

Abstract

We evaluated human physiological responses and the performance of manual tasks during exposure to severe cold (-25 degrees C) at night (0300-0500 hours) and in the afternoon (1500-1700 hours). Thirteen male students wearing standard cold protective clothing occupied a severely cold room (-25 degrees C) for 20 min, and were then transferred to a cool room (10 degrees C) for 20 min. This pattern of exposure was repeated three times, for a total time of exposure to extreme cold of 60 min. The experiments were started either at 1500 hours or 0300 hours and measurements of rectal temperature, skin temperature, blood pressure, performance in a counting task, hand tremor, and subjective responses were made in each condition. At the end of the experiment at night the mean decrease in rectal temperature [0.68 (SEM 0.04) degree C] was significantly greater than that at the end of the experiment in the afternoon [0.55 (SEM 0.08) degree C, P < 0.01]. After the second cold exposure at night the mean increase in diastolic blood pressure [90 (SEM 2.0) mmHg] was significantly greater than that at the end of the second cold exposure in the afternoon [82 (SEM 2.8) mmHg, P < 0.01]. At the end of the second cold exposure at night, mean finger skin temperature [11.8 (SEM 0.8) degrees C] was significantly higher than that at the comparable time in the afternoon [9.0 (SEM 0.7) degrees C, P < 0.01]. Similarly for the toe, mean skin temperature at the start of the second cold exposure at night [25.6 (SEM 1.5) degrees C] was significantly higher than in the afternoon [20.1 (SEM 0.8) degrees C, P < 0.01]. The increased skin temperatures in the periphery resulted in increased heat loss. Since peripheral skin temperatures were highest at night, the subjects noted diminished sensations of thermal cold and pain at that time. Manual dexterity at the end of the first cold exposure at night [mean 83.7 (SEM 3.6) times.min-1] had decreased significantly more than at the end of the first cold exposure in the afternoon [mean 89.4 (SEM 3.5) times.min-1, P < 0.01]. These findings of a lowered rectal temperature and diminished manual dexterity suggest that there is an increased risk of both hypothermia and accidents for those who work at night.

Blood pressure and thermal responses to repeated whole body cold exposure: effect of winter clothing

“…The level of maximal blood pressure was reached 5 min after the starting of the cold exposure, and blood pressure stayed almost at the same level during the 15-min cold exposure. SBP and DBP responses in the present study were in accordance with previous studies (Ozaki et al 1998(Ozaki et al , 2001, which have been carried out with normotensive participants in warmer winter clothing (2.3 clo) under colder test conditions. SBP has been reported to increase from 118 to 126, 129, and 128.5 mmHg after the first, second and third 20-min exposure to -25°C with 20-min warm up in 30°C between two cold exposures (Ozaki et al 1998).…”

“…Numerous studies have been conducted to demonstrate the effects of long-term exposure to cold (Leppaluoto et al 2001;Makinen et al 2006;Reynolds et al 2007). On the other hand, investigations of the effects of short-term repeated cold exposures on health and physiological responses are limited in number (Ozaki et al 1998(Ozaki et al , 2001Tochihara 2005;Kim et al 2007). However, these short cold exposures are very common in daily life during winter and have become more increasingly common in industry.…”

Heat Acclimation and Performance in Hypoxic Conditions

“…This factor was not within the scope of this study, but should be considered in future studies since it has its own specifi c effects on both cognitive ( 17 ) and physiological ( 20 ) performances, and since the interactions between heat and cold, which have not actually been widely studied, have not always shown conclusive results ( 22 , 27 ). Therefore, adding the cold factor to the cross adaptation " equation " is defi nitely a scientifi c and applicative challenge.…”

Age-Differentiated Work Systems

“…According to Tochihara et al (1995) and Ozaki et al (2001), due to peripheral vasoconstriction, pronounced increases in blood pressure could be measured as physiological responses to cold exposures. Starting from the basal blood pressure (the lowest value in the morning) and the intermittently recorded blood pressure, physiological reactions in the form of substantial increases, indeed, occur under static and dynamic stress in addition to circadian fluctuations.…”

“…Ozaki et al 2001) investigated that the blood pressure rises substantially with cold stress. Firstly, the additional weight of the cold-protective clothing can stimulate the body's blood circulation.…”