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

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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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Funding

Canadian Foundation for Innovation: Leader’s Opportunity Fund (DSK), Faculty of Health Professions Research Development (DSK), and Nova Scotia Health Research Foundation (NSHRF) Development/Innovation (DSK) Grants. MWO was supported by a Heart & Stroke BrightRed Scholarship, Nova Scotia Graduate Scholarship, an NSHRF Scotia Scholars Award, and a Killam PreDoctoral Scholarship.

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Authors and Affiliations

  1. Autonomic Cardiovascular Control and Exercise Laboratory, Division of Kinesiology, School of Health and Human Performance, Faculty of Health, Dalhousie University, 6230 South Street, Halifax, NS, B3H 4R2, Canada

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

Authors
  1. Myles W. O’Brien
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  2. Diane Ramsay
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  3. William Johnston
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  4. Derek S. Kimmerly
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Contributions

MWO and DSK conceived and designed the study. All authors were involved with data collection. MWO created the neurovascular transduction analysis program and analyzed the data. MWO and DSK interpreted the data. MWO drafted the manuscript. All authors revised and approved the final manuscript.

Corresponding author

Correspondence to Derek S. Kimmerly.

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Conflict of interest

The authors have no conflicts of interest to report.

Ethical approval

Research ethics board approval was attained from Dalhousie University. Participants provided written, informed consent prior to study enrollment.

Electronic supplementary material

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10286_2020_734_MOESM1_ESM.tif

Supplemental Figure 1. The relationship between peak relative activity and the peak pressor responses for total peripheral resistance (TPR; panel A), mean arterial pressure (MAP; panel B) and cardiac output (CO; C). Data were analyzed by burst pattern including singlets (circles), doublets (triangles) and triplets+ (squares. Within each burst pattern, data were ordered based on burst sequence amplitude quartiles denoted by Q1 (black), Q2 (dark grey), Q3 (light grey), and Q4 (white). Data presented as means ± standard deviations. The relationship between peak relative activity (%) and the peak pressor responses were determined via Pearson correlations for each variable (TIF 13300 kb)

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O’Brien, M.W., Ramsay, D., Johnston, W. et al. Aerobic fitness and sympathetic responses to spontaneous muscle sympathetic nerve activity in young males. Clin Auton Res 31, 253–261 (2021). https://doi.org/10.1007/s10286-020-00734-w

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  • DOI: https://doi.org/10.1007/s10286-020-00734-w

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