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Independent and combined impact of hypoxia and acute inorganic nitrate ingestion on thermoregulatory responses to the cold

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journal contribution
posted on 09.02.2021, 11:55 by Josh ArnoldJosh Arnold, Stephen BaileyStephen Bailey, Simon HodderSimon Hodder, Naoto Fujii, Alex LloydAlex Lloyd
Purpose: This study assessed the impact of normobaric hypoxia and acute nitrate ingestion on shivering thermogenesis, cutaneous vascular control and thermometrics in response to cold stress. Method: Eleven male volunteers underwent passive cooling at 10°C air temperature across four conditions: 1) normoxia with placebo ingestion, 2) hypoxia (0.130 FiO2) with placebo ingestion, 3) normoxia with 13 mmol nitrate ingestion, 4) hypoxia with nitrate ingestion. Physiological metrics were assessed as a rate of change over 45-mins to determine heat loss, and at the point of shivering onset to determine thermogenic thermoeffector threshold. Result: Independently, hypoxia expedited shivering onset time (p = 0.05) due to a faster cooling rate as opposed to a change in central thermoeffector thresholds. Specifically, compared to normoxia, hypoxia increased skin blood flow (p = 0.02), leading to an increased core-cooling rate (p = 0.04) and delta change in rectal temperature (p = 0.03) over 45-mins, yet the same rectal temperature at shivering onset (p = 0.9). Independently, nitrate ingestion delayed shivering onset time (p = 0.01), mediated by a change in central thermoeffector thresholds, independent of changes in peripheral heat exchange. Specifically, compared to placebo ingestion, no difference was observed in skin blood flow (p = 0.5), core-cooling rate (p = 0.5) or delta change in rectal temperature (p = 0.7) over 45-mins, while nitrate reduced rectal temperature at shivering onset (p = 0.04). No interaction was observed between hypoxia and nitrate ingestion. Conclusion: This data improves our understanding of how hypoxia and nitric oxide modulate cold thermoregulation.

History

School

  • Sport, Exercise and Health Sciences

Published in

European Journal of Applied Physiology

Volume

121

Issue

4

Pages

1207-1218

Publisher

Springer Verlag

Version

VoR (Version of Record)

Rights holder

© The Authors

Publisher statement

This is an Open Access Article. It is published by Springer under the Creative Commons Attribution 4.0 Unported Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/

Acceptance date

10/01/2021

Publication date

2021-02-09

Copyright date

2021

ISSN

1439-6319

eISSN

1439-6327

Language

en

Depositor

Mr Josh Arnold. Deposit date: 26 December 2020