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Clinical Autonomic Research

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01-04-2021 | Research Article

Aerobic fitness and sympathetic responses to spontaneous muscle sympathetic nerve activity in young males

Authors: Myles W. O’Brien, Diane Ramsay, William Johnston, Derek S. Kimmerly

Published in: Clinical Autonomic Research | Issue 2/2021

Abstract

Purpose

Lower aerobic fitness increases the risk of developing hypertension. Muscle sympathetic nerve activity (MSNA) is important for the beat-by-beat regulation of blood pressure. Whether the cardiovascular consequences of lower aerobic fitness are due to augmented transduction of MSNA into vascular responses is unclear. We tested the hypothesis that aerobic fitness is inversely related to peak increases in total peripheral resistance (TPR) and mean arterial pressure (MAP) in response to spontaneous MSNA bursts in young males.

Methods

Relative peak oxygen consumption (VO₂peak, indirect calorimetry) was assessed in 18 young males (23 ± 3 years; 41 ± 8 ml/kg/min). MSNA (microneurography), cardiac intervals (electrocardiogram) and arterial pressure (finger photoplethysmography) were recorded continuously during supine rest. Stroke volume and cardiac output (CO) were estimated via the ModelFlow method. TPR was calculated as MAP/CO. Changes in TPR and MAP were tracked for 12 cardiac cycles following heartbeats associated with or without spontaneous bursts of MSNA.

Results

Overall, aerobic fitness was inversely correlated to the peak ΔTPR (0.8 ± 0.7 mmHg/l/min; R = − 0.61, P = 0.007) and ΔMAP (2.3 ± 0.8 mmHg; R = − 0.69, P < 0.001), but not with the peak ΔCO (0.2 ± 0.1 l/min; P = 0.50), MSNA burst frequency (14 ± 5 bursts/min; P = 0.43) or MSNA relative burst amplitude (65 ± 12%; P = 0.13). Heartbeats without an associated burst of MSNA did not increase TPR, MAP or CO.

Conclusion

Although unrelated to traditional MSNA characteristics, aerobic fitness was inversely associated with spontaneous sympathetic neurovascular transduction in young males. This may be a potential mechanism by which aerobic fitness modulates the regulation of arterial blood pressure through the sympathetic nervous system.

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Title: Aerobic fitness and sympathetic responses to spontaneous muscle sympathetic nerve activity in young males
Authors: Myles W. O’Brien
Diane Ramsay
William Johnston
Derek S. Kimmerly
Publication date: 01-04-2021
Publisher: Springer Berlin Heidelberg
Published in: Clinical Autonomic Research / Issue 2/2021
Print ISSN: 0959-9851
Electronic ISSN: 1619-1560
DOI: https://doi.org/10.1007/s10286-020-00734-w

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Springer Medicine

Aerobic fitness and sympathetic responses to spontaneous muscle sympathetic nerve activity in young males

Abstract

Purpose

Methods

Results

Conclusion

Keynote webinar | Spotlight on medication adherence

Springer Medicine

Abstract

Purpose

Methods

Results

Conclusion

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