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Microneurographic characterization of sympathetic responses during 1-leg exercise in young and middle-aged humans

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posted on 09.08.2018, 13:46 by Catherine F. Notarius, Philip J. Millar, Connor J. Doherty, Anthony V. Incognito, Nobuhiko Haruki, Emma ODonnellEmma ODonnell, John S. Floras
Muscle sympathetic nerve activity (MSNA) at rest increases with age. However, the influence of age on MSNA recorded during dynamic leg exercise is unknown. We tested the hypothesis that aging attenuates the sympatho-inhibitory response observed in young subjects performing mild to moderate 1-leg cycling. After pre-determining peak oxygen uptake (VO2peak), we compared contra-lateral fibular nerve MSNA during 2 minutes each of mild (unloaded) and moderate (30-40% of the work rate at peak VO2, halved for single leg) 1-leg cycling in 18 young (23±1 years [mean±SE]) and 18 middle-aged (57±2 years) sex-matched healthy subjects. Mean height, weight, resting heart rate (HR), systolic blood pressure (BP) and percent predicted VO2peak were similar between groups. Middle-aged subjects had higher resting MSNA burst frequency and incidence (P<0.001) and diastolic BP (P=0.04). During moderate 1-leg cycling, older subjects’ systolic BP increased more (+21±5 vs.+10±1 mmHg; P=0.02) and their fall in MSNA burst incidence was amplified (-19±2 vs. -11±2 bursts/100heartbeats; P=0.01) but because HR rose less (+153 vs.+192 bpm; P=0.03), exercise induced similar reductions in burst frequency (P=0.25). Contrary to our initial hypothesis, with advancing age, mild to moderate intensity dynamic leg exercise elicits a greater rise in systolic BP and a larger fall in MSNA.


This study was supported by operating grants from the Heart and Stroke Foundation of Ontario (T4938, NA6298), the Canadian Institutes of Health Research (PJT148836), and the Natural Science and Engineering Council of Canada (06019).



  • Sport, Exercise and Health Sciences

Published in

Applied Physiology, Nutrition, and Metabolism


NOTARIUS, C.F. ... et al., 2018. Microneurographic characterization of sympathetic responses during 1-leg exercise in young and middle-aged humans. Applied Physiology, Nutrition, and Metabolism, In Press.


© NRC Research Press


AM (Accepted Manuscript)

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This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

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This paper was accepted for publication in the journal Applied Physiology, Nutrition, and Metabolism and the definitive published version is available at https://doi.org/10.1139/apnm-2018-0101





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