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Autonomic nervous control of the heart rate response to dynamic incremental exercise: evaluation of the Rosenblueth-Simeone model
Authors:Jorge Pinto Ribeiro  José Manuel Ibáñez  Ricardo Stein
Affiliation:(1) Exercise Research Laboratory, Federal University of Rio Grande do Sul, Rua Felizardo 750, 90610 Porto Alegre, Brazil;(2) Cardiology Division, Hospital de Clinicas de Porto Alegre, Porto Alegre, Brazil
Abstract:Summary To evaluate the validity of the Rosenblueth-Simeone model for the heart rate response to incremental dynamic exercise, 11 healthy men performed maximal exercise tests on a cycle ergometer after administration of placebo, propranolol, atropine or both propranolol and atropine. The model showed that the influence of sympathetic activity on heart rate increased at intensities up to those which resulted in a heart rate 70% maximal heart rate on placebo, and levelled off at higher intensities, while there was a progressive withdrawal of the parasympathetic activity. The ratio between heart rate predicted by the model and the recorded heart rate following placebo treatment tended to be less than 1.0 at lower exercise intensities, and approached the unit at intensities above those which resulted in a heart rate higher than 70% of maximal heart rate on placebo. There was a strong correlation (r=0.94,P<0.01) between the heart rate on placebo and the heart rate estimated by the model. Nevertheless, there was some scattering of the data around the identity line, with a standard error of the estimate for the regression line of 11 beats · min–1. Thus, during incremental exercise, the influence of sympathetic activity on heart rate does not become progressively more important at higher exercise intensities. The application of the Rosenblueth-Simeone model shows limitations during incremental exercise, particularly at low exercise intensities.
Keywords:Autonomic nervous system  Propranolol  Atropine  Intrinsic heart rate
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