Affiliation:
1. Human Cardiovascular Physiology Laboratory, Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
Abstract
The effects of sympathetic activity on vasoconstriction are dampened in active skeletal muscle during exercise, a phenomenon termed functional sympatholysis. Limited work has examined the influence of sex on the magnitude of sympatholysis or the test-retest reliability of measurements. In 16 women and 15 men, forearm blood flow (FBF; Doppler ultrasound), muscle oxygenation (near-infrared spectroscopy, NIRS), and beat-to-beat mean arterial pressure (MAP; photoplethysmography) were measured during lower-body negative pressure (LBNP; −20 mmHg) at rest and simultaneously during rhythmic handgrip exercise (30% maximum contraction). Measures were taken twice within the same visit (separated by 15 min) and repeated on a second visit. Forearm vascular conductance (FVC) was calculated as FBF/MAP. The magnitude of sympatholysis was calculated as the difference of LBNP-induced changes between handgrip and rest. LBNP decreased FBF (Δ−45 ± 15%), FVC (Δ−45 ± 16%), and muscle oxygenation (Δ−14 ± 11%); however, these responses were attenuated when LBNP was applied during rhythmic handgrip exercise (Δ−7 ± 9%, Δ−9 ± 10%, and Δ−6 ± 9%, respectively). The magnitude of sympatholysis was not different between men and women (FBF: 40 ± 16% vs. 35 ± 9%, P = 0.37; FVC: 38 ± 16% vs. 35 ± 11%, P = 0.53; muscle oxygenation: 5 ± 9% vs. 11 ± 10%, P = 0.11). Furthermore, sympatholysis measurements demonstrated good to excellent intraday (intraclass-correlation coefficients; ICC ≥ 0.85) and interday (ICC ≥ 0.72) test-retest reliability (all P ≤ 0.01) in both sexes. The coefficients of variation were larger with NIRS (68–91%) than with Doppler ultrasound (16%−22%) assessments of functional sympatholysis. Collectively, these findings demonstrate that assessments of functional sympatholysis are not impacted by biological sex and that Doppler ultrasound-derived measures of sympatholysis have better within-subject reliability than NIRS-derived measures in young healthy adults.
Funder
Gouvernement du Canada | Natural Sciences and Engineering Research Council of Canada
MDECEC | Ontario Ministry of Research and Innovation
Canada Foundation for Innovation
Gouvernement du Canada | Canadian Institutes of Health Research
Ontario Ministry of Economic Development, Job Creation and Trade
Publisher
American Physiological Society
Subject
Physiology (medical),Physiology
Cited by
11 articles.
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