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Effect of the duration of daily aerobic physical training on cardiac autonomic adaptations.
MedLine Citation:
PMID:  20708981     Owner:  NLM     Status:  In-Process    
Abstract/OtherAbstract:
The present study has investigated in conscious rats the influence of the duration of physical training sessions on cardiac autonomic adaptations by using different approaches; 1) double blockade with methylatropine and propranolol; 2) the baroreflex sensitivity evaluated by alternating bolus injections of phenylephrine and sodium nitroprusside; and 3) the autonomic modulation of HRV in the frequency domain by means of spectral analysis. The animals were divided into four groups: one sedentary group and three training groups submitted to physical exercise (swimming) for 15, 30, and 60min a day during 10 weeks. All training groups showed similar reduction in intrinsic heart rate (IHR) after double blockade with methylatropine and propranolol. However, only 30-min and 60-min physical training presented an increase in the vagal autonomic component for determination of basal heart rate (HR) in relation to group sedentary. Spectral analysis of HR showed that the 30-min and 60-min physical training presented the reduction in low-frequency oscillations (LF=0.20-0.75Hz) and the increase in high-frequency oscillations (HF=0.75-2.5Hz) in normalized units. These both groups only showed an increased baroreflex sensitivity to tachycardiac responses in relation to group sedentary, however when compared, the physical training of 30-min exhibited a greater gain. In conclusion, cardiac autonomic adaptations, characterised by the increased predominance of the vagal autonomic component, were not proportional to the duration of daily physical training sessions. In fact, 30-minute training sessions provided similar cardiac autonomic adaptations, or even more enhanced ones, as in the case of baroreflex sensitivity compared to 60-minute training sessions.
Authors:
Janaina E Sant'Ana; Marília G A G Pereira; Valdo J Dias da Silva; Camila Dambrós; Claudio M Costa-Neto; Hugo C D Souza
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-08-13
Journal Detail:
Title:  Autonomic neuroscience : basic & clinical     Volume:  159     ISSN:  1872-7484     ISO Abbreviation:  Auton Neurosci     Publication Date:  2011 Jan 
Date Detail:
Created Date:  2010-12-14     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100909359     Medline TA:  Auton Neurosci     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  32-7     Citation Subset:  IM    
Copyright Information:
Copyright © 2010 Elsevier B.V. All rights reserved.
Affiliation:
Exercise Physiology Laboratory, Department of Biomechanics and Rehabilitation, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, SP, Brazil.
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