Document Detail

Loss of resting bradycardia with detraining is associated with intrinsic heart rate changes.
MedLine Citation:
PMID:  16007286     Owner:  NLM     Status:  MEDLINE    
The mechanisms underlying the loss of resting bradycardia with detraining were studied in rats. The relative contribution of autonomic and non-autonomic mechanisms was studied in 26 male Wistar rats (180-220 g) randomly assigned to four groups: sedentary (S, N = 6), trained (T, N = 8), detrained for 1 week (D1, N = 6), and detrained for 2 weeks (D2, N = 6). T, D1 and D2 were treadmill trained 5 days/week for 60 min with a gradual increase towards 50% peak VO2. After the last training session, D1 and D2 were detrained for 1 and 2 weeks, respectively. The effect of the autonomic nervous system in causing training-induced resting bradycardia and in restoring heart rate (HR) to pre-exercise training level (PET) with detraining was examined indirectly after cardiac muscarinic and adrenergic receptor blockade. T rats significantly increased peak VO2 by 15 or 23.5% when compared to PET and S rats, respectively. Detraining reduced peak VO2 in both D1 and D2 rats by 22% compared to T rats, indicating loss of aerobic capacity. Resting HR was significantly lower in T and D1 rats than in S rats (313 +/- 6.67 and 321 +/- 6.01 vs 342 +/- 12.2 bpm) and was associated with a significantly decreased intrinsic HR (368 +/- 6.1 and 362 +/- 7.3 vs 390 +/- 8 bpm). Two weeks of detraining reversed the resting HR near PET (335 +/- 6.01 bpm) due to an increased intrinsic HR in D2 rats compared with T and D1 rats (376 +/- 8.8 bpm). The present study provides the first evidence of intrinsic HR-mediated loss of resting bradycardia with detraining in rats.
F S Evangelista; S E D Martuchi; C E Negrão; P C Brum
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2005-07-04
Journal Detail:
Title:  Brazilian journal of medical and biological research = Revista brasileira de pesquisas médicas e biológicas / Sociedade Brasileira de Biofísica ... [et al.]     Volume:  38     ISSN:  0100-879X     ISO Abbreviation:  Braz. J. Med. Biol. Res.     Publication Date:  2005 Jul 
Date Detail:
Created Date:  2005-07-11     Completed Date:  2006-01-09     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8112917     Medline TA:  Braz J Med Biol Res     Country:  Brazil    
Other Details:
Languages:  eng     Pagination:  1141-6     Citation Subset:  IM    
Departamento de Biodinâmica do Movimento do Corpo Humano, Escola de Educação Física e Esporte, Universidade de São Paulo, SP, Brasil.
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MeSH Terms
Autonomic Nervous System / physiology*
Bradycardia / physiopathology*
Heart Rate / physiology*
Oxygen Consumption / physiology
Physical Conditioning, Animal / physiology*
Random Allocation
Rats, Wistar
Rest / physiology*

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