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Cardiovascular, autonomic, and thermoregulatory effects of repeated exertional heat stress in rats
Author(s) -
Stauss Harald M,
Choudhary Navita,
Nash Abigail,
Liaboe Frederick O,
Kregel Kevin C
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.1079.3
Subject(s) - medicine , acclimatization , heart rate , nocturnal , core temperature , blood pressure , autonomic nervous system , thermoregulation , heart rate variability , cardiology , endocrinology , heat stress , zoology , biology , botany
A single bout of exercise in the heat (ExHS) produces specific alterations in autonomic function. This study aimed to investigate the effects of multiple bouts of ExHS (10 ExHS bouts over 5 days; 2x/day). Rats (n=8) were run on a motorized running wheel (7–11 m/min) at 39°C until core temperature (T c ) reached 41.8°C. Blood pressure (BP), heart rate (HR) and T c were recorded telemetrically for 3 days before, during, and 3 days after the ExHS protocol. Both low frequency (LF) HR variability (HR LF ) and LF systolic BP (SBP) variability (SBP LF ) increased from baseline values in the night following the first protocol day and remained elevated during the nights following the remaining 4 days of ExHS. Compared to baseline (and controls), HR and T c were temporarily elevated in the night following the first protocol day (368±11 vs. 317±4 bpm and 38.8±0.04 vs. 37.7±0.08°C) but returned to baseline in the night following the fifth protocol day, suggesting a training and heat acclimation effect. HR‐related measures suggested no changes in cardiac parasympathetic modulation occurred with ExHS. The elevated nocturnal HR LF and SBP LF throughout the ExHS protocol, together with the blunted HR and T c responses at the end of the ExHS protocol, suggest that chronic exposure to ExHS can lead to a sustained increase in cardiac and vascular sympathetic activity despite training and heat acclimation. Supported by DoD/USAMRMC #W81XWH‐10‐2‐0115.