Females exposed to 24 hours of sleep deprivation do not experience greater physiological strain, but do perceive heat illness symptoms more severely, during exercise-heat stress

There is limited and inconclusive evidence surrounding the physiological and perceptual responses to heat stress while sleep deprived, especially for females. This study aimed to quantify the effect of 24-hrs sleep deprivation on physiological strain and perceptual markers of heat-related illness in females. Method: Nine females completed two 30 min heat stress tests (HST) separated by 48 hrs in 39°C, 41% relative humidity at a metabolic heat production of 10 W.kg-1. The non-sleep deprived HST was followed by the sleep deprivation (SDHST) trial for all participants, during the follicular phase of the menstrual cycle. Physiological and perceptual measures were recorded at 5 min intervals during the HSTs. On the cessation of the HSTs, heat illness symptom index (HISI) was completed.Results: HISI scores increased after sleep deprivation by 28±16 vs. 20±16 (P=0.01). Peak (39.40±0.35°C vs. 39.35±0.33°C) and change in rectal temperature (1.91±0.21 vs. 1.93±0.34°C), and whole body sweat rate (1.08±0.31 vs. 1.15±0.36 L.h-1) did not differ (P>0.05) between tests. No difference was observed in peak, nor rise in; heart rate, mean skin temperature, perceived exertion or thermal sensation during the HSTs.Conclusion: 24 hrs sleep deprivation increased perceptual symptoms associated with heat-related illness, however, no thermoregulatory alterations were observed.