Evidence of viscerally-mediated cold-defence thermoeffector responses in man
journal contributionposted on 24.11.2016, 09:41 by Nathan B. Morris, Davide Filingeri, Mark Halaki, Oliver E. Jay
Sudomotor activity is modified by both warm and cold fluid ingestion during heat stress, independently of differences in core and skin temperatures, suggesting independent viscerally-mediated modification of thermoeffectors. The purpose of the present study was to determine whether visceral thermoreceptors modify shivering responses to cold stress. Ten males (27 ± 5y, 1.73 ± 0.06 m, 78.4 ± 10.7 kg) underwent whole-body cooling via 5 °C water perfusion-suit, on four occasions, to induce a steady-state shivering response, at which point two aliquots of 1.5 ml/kg (SML) and 3.0 ml/kg (LRG), separated by 20- min, of either 7°C, 22°C, 37°C or 52°C water were ingested. Rectal, mean skin and mean body temperature (Tb), electromyographic activity (EMG), metabolic rate (M) and whole-body thermal sensation on a visual analogue scale (WBTS) ranging from 0 mm [very cold] to 200 mm [very hot] were all measured throughout. Tb was not different between all fluid temperatures following SML (7°C:35.7 ± 0.5°C, 22°C:35.6 ± 0.5°C, 37°C:35.5 ± 0.4°C, 52°C:35.5 ± 0.4°C; P = 0.27) or LRG (7°C:35.3 ± 0.6°C, 22°C:35.3 ± 0.5°C, 37°C:35.2 ± 0.5°C, 52°C:35.3 ± 0.5°C; P = 0.99) fluid ingestion. With SML ingestion, greater metabolic rate and cooler thermal sensations were observed with 7°C (M:179 ± 55 W, WBTS:29 ± 21 mm) compared to 52°C (M:164 ± 34 W, WBTS:51 ± 28 mm; all P < 0.05) ingestion. With LRG ingestion, compared to shivering and thermal sensations with 37 °C ingestion (M:215 ± 47 W, EMG:3.9 ± 2.5%MVC, WBTS:33 ± 2 mm) values were different (all P < 0.05) following 7°C (M:269 ± 77 W, EMG:5.5 ± 0.9%MVC, WBTS:14 ± 12 mm), 22°C (M:270 ± 86 W, EMG:5.6 ± 1.0%MVC, WBTS:18 ± 19 mm) and 52°C (M:179 ± 34 W, EMG:3.3 ± 2.1%MVC, WBTS:53 ± 28 mm) ingestion. In conclusion, ingesting 52°C fluids decreased shivering and the sensation of coolness, whereas 22°C and 7°C fluids increased shivering and sensations of coolness to similar levels, independently of core and skin temperature.
Dr. Filingeri was supported by a Government of Australia - Endeavour Post-Doctoral Research Fellowship. Mr. Morris was supported by a Australian Department of Industry International Postgraduate Research Scholarship.
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