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Sport Modality Affects Bradycardia Level and Its Mechanisms of Control in Professional Athletes
DOI 10.1055/s-0033-1364024 Int J Sports Med For personal use only. No commercial use, no depositing in repositories.
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IJSM/3708/26.5.2014/MPS
Clinical Sciences
Sport Modality Affects Bradycardia Level and Its Mechanisms of Control in Professional Athletes
Authors
L. F. Azevedo1, P. S. Perlingeiro1, D. T. Hachul2, I. L. Gomes-Santos1, P. C. Brum3, T. G. Allison5, C. E. Negrão1, 3, L. D. N. J. De Matos1, 4
Affiliations
Affiliation addresses are listed at the end of the article
Key words ▶ heart rate ● ▶ autonomic nervous system ● ▶ sinus node ● ▶ exercise training ●
Abstract
accepted after revision December 03, 2013 Bibliography DOI http://dx.doi.org/ 10.1055/s-0033-1364024 Published online: 2014 Int J Sports Med © Georg Thieme Verlag KG Stuttgart · New York ISSN 0172-4622 Correspondence Luciene Ferreira Azevedo Heart Institute (InCor) Medical School of University of Sao Paulo Cardiovascular Rehabilitation and Exercise Physiology Unit Av. Dr Eneas de Carvalho Aguiar 44, Bloco II, 1°SS, Sao Paulo SP 05403900 Brazil Tel.: + 55/112 6615 043 Fax: + 55/112 6615 043
[email protected]
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We investigated the influence of sport modalities in resting bradycardia and its mechanisms of control in highly trained athletes. In addition, the relationships between bradycardia mechanisms and cardiac structural adaptations were tested. Professional male athletes (13 runners, 11 cyclists) were evaluated. Heart rate (HR) was recorded at rest on beat-to-beat basis (ECG). Selective pharmacological blockade was performed with atropine and esmolol. Vagal effect, intrinsic heart rate (IHR), parasympathetic (n) and sympathetic (m) modulations, autonomic influence (AI) and autonomic balance (Abal) were calculated. Plasmatic norepinephrine (high-pressure liquid chromatography) and cardiac structural adaptations (echocardiography) were evaluated. Runners presented lower resting
Introduction
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Resting sinus bradycardia is considered to be the hallmark of high-intensity aerobic exercise training, but its level and the mechanisms underlying this cardiac adaptation in professional athletes require further understanding. While a large number of athletes have mild bradycardia ranging from 51 to 60 beats.min − 1 [6, 14, 17, 27, 29], resting heart rate (HR) as low as 25 beats.min − 1 has been reported in highly trained athletes [5]. Some authors observed increased vagal modulation as the main mechanism associated with bradycardia in athletes [6, 24, 30]. Nevertheless, the non-autonomic changes, such as a reduced intrinsic heart rate (IHR) mainly due to sinus node change [14, 17, 27], have been demonstrated and shed light on non-autonomic mechanisms underlying sinus bradycardia [3]. Based on these two important mechanisms, we cannot rule out the possibility of a balance between autonomic and non-autonomic mechanisms or a presence of temporal adaptation in endurance athletes. The
HR, higher vagal effect, parasympathetic modulation (n), AI and IHR than cyclists (P
