Heated environment increases blood pressure drop and postural sway during initial orthostasis in healthy subjects.

Autor: Ferreira FC; Laboratory of Experimental and Applied Exercise Physiology, Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, RJ, Brazil.; Clinical Research Unit in Neurology and Neurosciences, Niterói, RJ, Brazil., Padilha MCSV; Laboratory of Experimental and Applied Exercise Physiology, Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, RJ, Brazil.; Clinical Research Unit in Neurology and Neurosciences, Niterói, RJ, Brazil., Araujo-Leite MA; Clinical Research Unit in Neurology and Neurosciences, Niterói, RJ, Brazil., da Silva Soares PP; Laboratory of Experimental and Applied Exercise Physiology, Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, RJ, Brazil., Rodrigues GD; Laboratory of Experimental and Applied Exercise Physiology, Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, RJ, Brazil. dias5gabriel@gmail.com.; Clinical Research Unit in Neurology and Neurosciences, Niterói, RJ, Brazil. dias5gabriel@gmail.com.
Jazyk: angličtina
Zdroj: European journal of applied physiology [Eur J Appl Physiol] 2024 Jun 27. Date of Electronic Publication: 2024 Jun 27.
DOI: 10.1007/s00421-024-05546-8
Abstrakt: Purpose: We tested the hypothesis that heat stress influences the closed-loop cardio-postural control by an increased blood pressure (BP) drop and postural sway.
Methods: Fourteen healthy individuals (eight women) performed two orthostatic tests under thermal reference (TC; ~ 24 ºC) and HOT (~ 38 ºC) conditions. The center-of-pressure (COP) displacements and the electromyography (EMG) activity of the calf muscles (medial gastrocnemius and tibialis anterior) were recorded during the initial orthostasis (ORT onset) after the supine-to-stand challenge. At the same period, BP (beat-to-beat) was continuously monitored, and supine-to-stand variations (∆%) were calculated. Sublingual temperature (Tsl) was measured as a surrogate of internal temperature.
Results: Tsl increased in HOT compared to TC (TC 36.5 ± 0.3 vs. HOT 36.7 ± 0.3 ºC; p < 0.01). COP distance was greater in HOT compared to TC condition (TC 596.6 ± 242.4 vs. HOT 680.2 ± 249.1 mm; p < 0.01). EMG activity of the gastrocnemius decreased in HOT compared to TC condition (TC 95.5 ± 19.8 vs. HOT 78.4 ± 22.8%mV; p = 0.02). EMG of tibialis did not change between TC and HOT (TC 83.5 ± 42.9 vs. HOT 66.1 ± 31.9% mV; p = 0.29). BP showed a greater fall in HOT compared to TC condition (∆%TC - 24.5 ± 13.2 vs. ∆%HOT - 33.2 ± 20.2%; p = 0.01).
Conclusion: Heat stress causes a greater fall in blood pressure and a reduction in musculoskeletal pump activity during orthostatic onset. These effects could be potential mechanisms that underlie augmented postural instability under a heated environment.
(© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)
Databáze: MEDLINE
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