- Meeting abstract
- Open access
- Published:
The impact of thermal pre-conditioning on cutaneous vasomotor and shivering thresholds
Extreme Physiology & Medicine volume 4, Article number: A117 (2015)
Introduction
The mean body temperature of resting, normothermic humans falls within the zone that separates the temperature thresholds for shivering and sweating; the vasomotor zone. Whilst these thresholds are often defined by their corresponding deep-body or mean body temperatures, it is well known that these are not set temperatures or points. Nevertheless, our knowledge concerning the factors that determine or modify these thresholds is imprecise. Therefore, the aim of this experiment was to investigate the effects of a deliberate modification of the pre-exposure mean body temperature on the subsequent vasomotor and shivering threshold temperatures. Mean body temperature was first displaced upwards, then slowly driven in the opposite direction, permitting the separate determination of these thermoeffector thresholds.
Methods
Eight males participated in two trials, each consisted of a pre-experimental, whole-body water immersion followed by passive cooling (experimental phase). Trials differed in the pre-experimental water temperature (45 min), with subjects either maintained in a normothermic (control: 34 °C) or a heated state (39 °C). Following pre-treatment and thermal clamping, subjects were passively cooled (water-perfusion garment) until 10 min beyond the onset of overt shivering. Deep-body and skin temperatures were recorded continuously, with skin blood flows (finger, forearm, calf; venous-occlusion plethysmography) and shivering (whole-body oxygen consumption) recorded during the experimental phase.
Results
Prior to cooling, mean body temperatures averaged 35.12 °C (±0.2; control) and 36.74 °C (±0.3; P < 0.05). The rate of passive cooling (mean body temperature) was not different between trials: 2.16°C.h-1 (±0.31; control) and 2.15°C.h-1 (±0.21; P > 0.05). In the control trial, each vasoconstrictor threshold occurred at a significantly higher mean body temperature than shivering. This was also evident following pre-heating, but now with each threshold being significantly elevated relative to the control trial. Furthermore, the shivering threshold displacement and the change in the pre-exposure mean body temperature were of an equivalent magnitude (P > 0.05).
Discussion
Given the level of experimental control, these threshold changes cannot be associated with between-trial differences in cooling rate. Instead, these observations are consistent with the possibility that thermoeffector thresholds may be as dependent upon the change in mean body temperature as they are upon its absolute value. Indeed, in a previous communication to this society [1], it was demonstrated that the sudomotor threshold was similarly linked with the size of the change in mean body temperature induced prior to commencing the experiment.
References
Caldwell JN, Nykvist Å, Powers N, Notley SR, Lee DS, Peoples GE, Taylor NAS: An investigation of forearm vasomotor and sudomotor thresholds during passive heating, following whole-body cooling. Proceedings of the Fourteenth International Conference on Environmental Ergonomics. Edited by: Kounalakis, S.N., and Koskolou, M. 2011, Nafplio, Greece. July 10th-15th, 132-135.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.
The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.
To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/.
The Creative Commons Public Domain Dedication waiver (https://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.
About this article
Cite this article
Caldwell, J.N., Nykvist, Å., Powers, N. et al. The impact of thermal pre-conditioning on cutaneous vasomotor and shivering thresholds. Extrem Physiol Med 4 (Suppl 1), A117 (2015). https://doi.org/10.1186/2046-7648-4-S1-A117
Published:
DOI: https://doi.org/10.1186/2046-7648-4-S1-A117