Individualising the exposure of -110°C whole body cryotherapy: The effects of sex and body composition.

The purpose of this study was to investigate the effects of whole body cryotherapy (WBC) on a range of thermoregulatory measures. We also sought to examine the influence of sex and body composition. A convenience sample of 18 healthy participants (10 males and 8 females) (27±6yr) volunteered for this study. Temperature (core, tympanic, skin and mean body), heart rate, blood pressure, and thermal comfort and sensation were recorded pre- and post- (immediately and every 5min until 35min post) exposure to a single bout of WBC (30s at -60°C, 150s at 110°C). Anthropometric data (height, weight, body surface area, body mass index, fat mass and fat free mass) were also recorded. No significant differences in temperature (core, tympanic, skin and mean body), heart rate, blood pressure, or thermal comfort / sensation were observed between male and females at baseline. Immediately post WBC mean body (male:31.9±0.8°C; female:31.0±0.9°C; ∆ mean body temperature:0.9±0.1°C; P≤0.05, d=0.64) and mean skin (male:22.1±2.2°C; female:19.6±2.8°C; ∆ mean skin temperature:-2.5±0.6°C; d=0.99, P≤0.05) temperature was significantly different between sexes. Sex differences were also observed in regional skin temperature (male thigh, 20.8±1.1°C; female thigh, 16.7±1.1°C, ∆ mean thigh skin temperature:-4.1°C; d=3.72; male calf, 20.5±1.1°C; female calf, 18.2±1°C, ∆ mean calf skin temperature:-2.3±0.1°C; d=3.61; male arm, 21.7±1°C; female arm, 19±0.4°C, ∆ mean arm skin temperature: -2.7±0.3°C; d=3.54; P≤0.05). Mean arterial pressure was significantly different over time (P≤0.001) and between sexes (male 0mins:94±10mmHg; female 0mins:85±7mmHg; male 35mins:88±7mmHg; female 35mins:80±6mmHg; P≤0.05). Combined data set indicated a strong negative relationship between skin temperature and body fat percentage 35min' post WBC (r=-0.749, P≤0.001) and for core temperature and body mass index in males only (r=0.726, P≤0.05) immediately after WBC. There were no significant differences between sexes in any other variables (heart rate, tympanic and perceptual variables). We observed sex differences in mean skin and mean body temperature following exposure to whole body cryotherapy. In an attempt to optimise treatment, these differences should be taken into account if whole body cryotherapy is prescribed.