Regulation of local sweating in sleep-deprived exercising humans

Abstract

Thermoregulatory sweating [total body (msw,b), chest (msw,c) and thigh (msw,t) sweating], body temperatures [oesophageal (T(oes)) and mean skin temperature (Tsk)] and heart rate were investigated in five sleep-deprived subjects (kept awake for 27 h) while exercising on a cycle (45 min at approximately 50% maximal oxygen consumption) in moderate heat (T(air) and T(wall) at 35 degrees C). The msw,c and msw,t were measured under local thermal clamp (Tsk,l), set at 35.5 degrees C. After sleep deprivation, neither the levels of body temperatures (T(oes), Tsk) nor the levels of msw,b, msw,c or msw,t differed from control at rest or during exercise steady state. During the transient phase of exercise (when Tsk and Tsk,l were unvarying), the msw,c and msw,t changes were positively correlated with those of T(oes). The slopes of the msw,c versus T(oes) or msw,t versus T(oes) relationships remained unchanged between control and sleep-loss experiments. Thus the slopes of the local sweating versus T(oes) relationships (msw,c and msw,t sweating data pooled which reached 1.05 (SEM 0.14) mg.cm-2.min-1.degree C-1 and 1.14 (SEM 0.18) mg.cm-2.min-1.degree C-1 before and after sleep deprivation) respectively did not differ. However, in our experiment, sleep deprivation significantly increased the T(oes) threshold for the onset of both msw,c and msw,t (+0.3 degrees C, P < 0.001). From our investigations it would seem that the delayed core temperature for sweating onset in sleep-deprived humans, while exercising moderately in the heat, is likely to have been due to alterations occurring at the central level.

Seasonal Effects of Sleep Deprivation on Thermoregulatory Responses in a Hot Environment

“…This result for sleep deprivation agreed with decreased M sw,t during exercise in air temperature of 28°C (Sawka et al 1983) but did not agree with increased M sw,t during exercise in air temperature of 35°C (Dewasmes et al 1992). It might be considered that the increase in M sw,t for sleep deprivation was minimized because the air temperature of 30°C in this study, which is lower than skin temperature, was advantageous to dry heat dissipation, besides the role of sleep deprivation in accelerating dry heat dissipation.…”

“…However, this DT re was the only seasonality of the thermoregulatory response that was found. A higher T sk for sleep deprivation during legbathing in this study was not in agreement with previous descriptions of no change in T sk between sleep deprivation and normal sleep during exercise (Dewasmes et al 1992;Kolka et al 1988;Sawka et al 1983). It was, however, in agreement with Opstad et al (1991), who found a higher T sk for sleep deprivation during exercise.…”

“…In experiments conducted at about 3:00 pm in the summer, Sawka et al (1984) reported that there was no change due to sleep loss in the threshold for sweating to begin, but that the gradient of sweating versus body temperature was reduced. A different study performed at about 11:00 am in the winter, on the other hand, found a higher threshold for sweating to begin and no change in the gradient of sweating versus body temperature (Dewasmes et al 1992). Another study at about 3:00 pm in the summer showed a lower body temperature at the onset of skin blood flow and a smaller slope of skin blood flow versus body temperature (Kolka et al 1988).…”

“…The findings on thermoregulatory responses, however, were inconsistent. Several investigators reported lower body temperature in a neutral environment after a sleep-deprived night (Kolka et al 1988;Landis et al 1998;Opstad et al 1991), while others showed increased body temperature (Bamezai et al 1992;Fiorica et al 1968) and still others showed no change in body temperature (Dewasmes et al 1992;Knauth et al 1978;Martin et al 1984;Savourey et al 1994;Sawka et al 1984). …”

One night of sleep deprivation decreases treadmill endurance performance

“…In fact, heart rate was actually shown to be reduced after sleep deprivation during sub-maximal exercise (Martin and Haney 1982;Martin and Gaddis 1981). Sleep deprivation has been shown to reduce evaporative cooling and dry heat loss in warm environments (Dewasmes et al 1993;Sawka et al 1984). Endurance performance was however not assessed in these investigations and therefore it is unclear whether the impaired heat dissipation mechanisms reported effect endurance performance.…”