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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 Orcid Logo, Jamie Scott, Jonathan Nixon, Stephen D. Patterson, Dawson Kidgell, Alan J. Pearce, Mark Waldron Orcid Logo, Jamie Tallent

European Journal of Applied Physiology

Swansea University Author: Mark Waldron Orcid Logo

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DOI (Published version): 10.1007/s00421-024-05616-x

Abstract

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) submaxima...

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Published in: European Journal of Applied Physiology
ISSN: 1439-6319 1439-6327
Published: Springer Science and Business Media LLC 2024
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa67731
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Abstract: 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.
College: Faculty of Science and Engineering
Funders: This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

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