Abstract
The potentiated exercise-sweating rate observed during acute hypoxia is diminished after a sleep-high train-low (SH-TL) regimen. We tested the hypothesis that this attenuation of the sweating response after SH-TL is compensated for by an increase in heat loss via vasodilatation. Nine male subjects participated in a 28-day SH-TL regimen. Before (pre-), and after (post-) the SH-TL protocol, they performed an \( \dot{V}{\text{O}}_{{ 2 {\text{peak}}}} \) test under normoxia and hypoxia. Additionally, pre- and post-SH-TL they completed three 30-min constant-work rate trials on a cycle ergometer. In one trial, the subjects inspired room air while exercising at 50 % of normoxic \( \dot{V}{\text{O}}_{{ 2 {\text{peak}}}} \) (CT). In the remaining trials, subjects exercised in hypoxia (FIO2 12.5 %), either at the same absolute (HAT) or relative (50 % of hypoxic \( \dot{V}{\text{O}}_{{ 2 {\text{peak}}}} \)) work rate (HRT) as in CT. Despite similar exercise core temperature responses between pre- and post-SH-TL trials, sweating rate was potentiated in HAT pre-SH-TL [CT: 1.97 (0.42); HRT: 1.86 (0.31); HAT: 2.55 (0.53) mg cm−2 min−1; p < 0.05]. Post-SH-TL exercise sweating rate was increased for CT, and remained unchanged in HRT and HAT [CT: 2.42 (0.76); HRT: 2.01 (0.33); HAT: 2.59 (0.30) mg cm−2 min−1]. Pre-SH-TL, the forearm-fingertip skin temperature difference (Tskf−f) was higher in HAT than in CT and HRT by ~3.5°C (p < 0.05). The inter-condition differences in Tskf−f were diminished post-SH-TL. In conclusion, the decrease in sweating rate during hypoxic exercise, following a SH-TL regimen, was countered by an increase in vasodilatation (reduced Tskf−f), whereas SH-TL enhanced the sweating response during normoxic exercise. The mechanisms underlying these SH-TL-induced alterations in thermoregulatory responses remain to be settled.
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Acknowledgments
We would like to thank all the subjects for their cooperation and patience. We are grateful to Bogomir Vrhovec and Mojca Amon for their valuable assistance. This study was supported by a grant from the Slovenian Research Agency (ARRS grant no. L7-2413) to Igor B. Mekjavic, and from b-Cat B.V. (The Netherlands) to Igor B. Mekjavic and Ola Eiken.
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The authors state that there is no personal conflict of interest in the present study.
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Communicated by George Havenith.
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Kounalakis, S.N., Eiken, O. & Mekjavic, I.B. Exercise thermoregulatory responses following a 28-day sleep-high train-low regimen. Eur J Appl Physiol 112, 3881–3891 (2012). https://doi.org/10.1007/s00421-012-2374-0
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DOI: https://doi.org/10.1007/s00421-012-2374-0