The effects of exercise, heat-induced hypo-hydration and rehydration on blood-brain-barrier permeability, corticospinal and peripheral excitability

Nasir Uddin; Jamie Scott; Jonathan Nixon; Stephen D. Patterson; Dawson Kidgell; Alan J. Pearce; Mark Waldron; Jamie Tallent

doi:10.1007/s00421-024-05616-x

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The effects of exercise, heat-induced hypo-hydration and rehydration on blood-brain-barrier permeability, corticospinal and peripheral excitability

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The effects of exercise, heat-induced hypo-hydration and rehydration on blood-brain-barrier permeability, corticospinal and peripheral excitability

Nasir Uddin, Jamie Scott, Jonathan Nixon, Stephen D. Patterson, Dawson Kidgell, Alan J. Pearce, Mark Waldron and Jamie Tallent

European journal of applied physiology, Vol.125, pp.535-550

2025

DOI: https://doi.org/10.1007/s00421-024-05616-x

PMCID: PMC11829906

PMID: 39340668

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Abstract

dehydration

neuromuscular function

thermoregulation

transcranial magnetic stimulation

rapid weight loss

Purpose The effects of low-intensity exercise, heat-induced hypo-hydration and rehydration on maximal strength and the underlying neurophysiological mechanisms are not well understood. Methods To assess this, 12 participants took part in a randomised crossover study, in a prolonged (3 h) submaximal (60 W) cycling protocol under 3 conditions: (i) in 45 °C (achieving ~ 5% body mass reduction), with post-exercise rehydration in 2 h (RHY2), (ii) with rehydration across 24 h (RHY24), and (iii) a euhydrated trial in 25 °C (CON). Dependent variables included maximal voluntary contractions (MVC), maximum motor unit potential (MMAX), motor evoked potential (MEPRAW) amplitude and cortical silent period (cSP) duration. Blood–brain-barrier integrity was also assessed by serum Ubiquitin Carboxyl-terminal Hydrolase (UCH-L1) concentrations. All measures were obtained immediately pre, post, post 2 h and 24 h. Results During both dehydration trials, MVC (RHY2: p < 0.001, RHY24: p = 0.001) and MEPRAW (RHY2: p = 0.025, RHY24: p = 0.045) decreased from pre- to post-exercise. MEPRAW returned to baseline during RHY2 and CON, but not RHY24 (p = 0.020). MEP/MMAX ratio decreased across time for all trials (p = 0.009) and returned to baseline, except RHY24 (p < 0.026). Increased cSP (p = 0.011) was observed during CON post-exercise, but not during RHY2 and RHY24. Serum UCH-L1 increased across time for all conditions (p < 0.001) but was not significantly different between conditions. Conclusion Our findings demonstrate an increase in corticospinal inhibition after exercise with fluid ingestion, but a decrease in corticospinal excitability after heat-induced hypo-hydration. In addition, low-intensity exercise increases peripheral markers of blood–brain-barrier permeability.

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Title: The effects of exercise, heat-induced hypo-hydration and rehydration on blood-brain-barrier permeability, corticospinal and peripheral excitability
Authors: Nasir Uddin (Corresponding Author) - St Mary's University Twickenham London
Jamie Scott - St Mary's University Twickenham London
Jonathan Nixon - St Mary's University Twickenham London
Stephen D. Patterson - St Mary's University Twickenham London
Dawson Kidgell - Monash University
Alan J. Pearce - Swinburne Univ Technol, Sch Hlth Sci, Swinburne Neuroimaging Facil, Melbourne, Australia
Mark Waldron - University of the Sunshine Coast, Queensland, School of Health and Behavioural Sciences - Legacy
Jamie Tallent - University of Essex
Publication details: European journal of applied physiology, Vol.125, pp.535-550
Publisher: Springer
Date published: 2025
DOI: 10.1007/s00421-024-05616-x
ISSN: 1439-6327
PMID: 39340668; PMC11829906
Copyright note: 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 http://creativecommons.org/licenses/by/4.0/.
Data Availability: The supporting data for this manuscript are available upon reasonable request to the authors.
Organisation Unit: School of Health
Language: English
Record Identifier: 991067191502621
Output Type: Journal article

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