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Heat acclimation reduces the effects of whole-body hyperthermia on knee-extensor relaxation rate, but does not affect voluntary torque production

PURPOSE: This study investigated the effects of acute hyperthermia and heat acclimation (HA) on maximal and rapid voluntary torque production, and their neuromuscular determinants. METHODS: Ten participants completed 10 days of isothermic HA (50 °C, 50% rh) and had their knee-extensor neuromuscular...

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Autores principales: Gordon, Ralph Joseph Frederick Hills, Moss, Jodie Natasha, Castelli, Federico, Reeve, Thomas, Diss, Ceri Elen, Tyler, Christopher James, Tillin, Neale Anthony
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Springer Berlin Heidelberg 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10119217/
https://www.ncbi.nlm.nih.gov/pubmed/36637508
http://dx.doi.org/10.1007/s00421-022-05127-7
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author Gordon, Ralph Joseph Frederick Hills
Moss, Jodie Natasha
Castelli, Federico
Reeve, Thomas
Diss, Ceri Elen
Tyler, Christopher James
Tillin, Neale Anthony
author_facet Gordon, Ralph Joseph Frederick Hills
Moss, Jodie Natasha
Castelli, Federico
Reeve, Thomas
Diss, Ceri Elen
Tyler, Christopher James
Tillin, Neale Anthony
author_sort Gordon, Ralph Joseph Frederick Hills
collection PubMed
description PURPOSE: This study investigated the effects of acute hyperthermia and heat acclimation (HA) on maximal and rapid voluntary torque production, and their neuromuscular determinants. METHODS: Ten participants completed 10 days of isothermic HA (50 °C, 50% rh) and had their knee-extensor neuromuscular function assessed in normothermic and hyperthermic conditions, pre-, after 5 and after 10 days of HA. Electrically evoked twitch and octet (300 Hz) contractions were delivered at rest. Maximum voluntary torque (MVT), surface electromyography (EMG) normalised to maximal M-wave, and voluntary activation (VA) were assessed during brief maximal isometric voluntary contractions. Rate of torque development (RTD) and normalised EMG were measured during rapid voluntary contractions. RESULTS: Acute hyperthermia reduced neural drive (EMG at MVT and during rapid voluntary contractions; P < 0.05), increased evoked torques (P < 0.05), and shortened contraction and relaxation rates (P < 0.05). HA lowered resting rectal temperature and heart rate after 10 days (P < 0.05), and increased sweating rate after 5 and 10 days (P < 0.05), no differences were observed between 5 and 10 days. The hyperthermia-induced reduction in twitch half-relaxation was attenuated after 5 and 10 days of HA, but there were no other effects on neuromuscular function either in normothermic or hyperthermic conditions. CONCLUSION: HA-induced favourable adaptations to the heat after 5 and 10 days of exposure, but there was no measurable benefit on voluntary neuromuscular function in normothermic or hyperthermic conditions. HA did reduce the hyperthermic-induced reduction in twitch half-relaxation time, which may benefit twitch force summation and thus help preserve voluntary torque in hot environmental conditions.
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spelling pubmed-101192172023-04-22 Heat acclimation reduces the effects of whole-body hyperthermia on knee-extensor relaxation rate, but does not affect voluntary torque production Gordon, Ralph Joseph Frederick Hills Moss, Jodie Natasha Castelli, Federico Reeve, Thomas Diss, Ceri Elen Tyler, Christopher James Tillin, Neale Anthony Eur J Appl Physiol Original Article PURPOSE: This study investigated the effects of acute hyperthermia and heat acclimation (HA) on maximal and rapid voluntary torque production, and their neuromuscular determinants. METHODS: Ten participants completed 10 days of isothermic HA (50 °C, 50% rh) and had their knee-extensor neuromuscular function assessed in normothermic and hyperthermic conditions, pre-, after 5 and after 10 days of HA. Electrically evoked twitch and octet (300 Hz) contractions were delivered at rest. Maximum voluntary torque (MVT), surface electromyography (EMG) normalised to maximal M-wave, and voluntary activation (VA) were assessed during brief maximal isometric voluntary contractions. Rate of torque development (RTD) and normalised EMG were measured during rapid voluntary contractions. RESULTS: Acute hyperthermia reduced neural drive (EMG at MVT and during rapid voluntary contractions; P < 0.05), increased evoked torques (P < 0.05), and shortened contraction and relaxation rates (P < 0.05). HA lowered resting rectal temperature and heart rate after 10 days (P < 0.05), and increased sweating rate after 5 and 10 days (P < 0.05), no differences were observed between 5 and 10 days. The hyperthermia-induced reduction in twitch half-relaxation was attenuated after 5 and 10 days of HA, but there were no other effects on neuromuscular function either in normothermic or hyperthermic conditions. CONCLUSION: HA-induced favourable adaptations to the heat after 5 and 10 days of exposure, but there was no measurable benefit on voluntary neuromuscular function in normothermic or hyperthermic conditions. HA did reduce the hyperthermic-induced reduction in twitch half-relaxation time, which may benefit twitch force summation and thus help preserve voluntary torque in hot environmental conditions. Springer Berlin Heidelberg 2023-01-13 2023 /pmc/articles/PMC10119217/ /pubmed/36637508 http://dx.doi.org/10.1007/s00421-022-05127-7 Text en © The Author(s) 2023 https://creativecommons.org/licenses/by/4.0/Open AccessThis 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 http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) .
spellingShingle Original Article
Gordon, Ralph Joseph Frederick Hills
Moss, Jodie Natasha
Castelli, Federico
Reeve, Thomas
Diss, Ceri Elen
Tyler, Christopher James
Tillin, Neale Anthony
Heat acclimation reduces the effects of whole-body hyperthermia on knee-extensor relaxation rate, but does not affect voluntary torque production
title Heat acclimation reduces the effects of whole-body hyperthermia on knee-extensor relaxation rate, but does not affect voluntary torque production
title_full Heat acclimation reduces the effects of whole-body hyperthermia on knee-extensor relaxation rate, but does not affect voluntary torque production
title_fullStr Heat acclimation reduces the effects of whole-body hyperthermia on knee-extensor relaxation rate, but does not affect voluntary torque production
title_full_unstemmed Heat acclimation reduces the effects of whole-body hyperthermia on knee-extensor relaxation rate, but does not affect voluntary torque production
title_short Heat acclimation reduces the effects of whole-body hyperthermia on knee-extensor relaxation rate, but does not affect voluntary torque production
title_sort heat acclimation reduces the effects of whole-body hyperthermia on knee-extensor relaxation rate, but does not affect voluntary torque production
topic Original Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10119217/
https://www.ncbi.nlm.nih.gov/pubmed/36637508
http://dx.doi.org/10.1007/s00421-022-05127-7
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