Physical Training, Bradycardia, and Autonomic Nervous System

Abstract

In order to study the bradycardia evoked by physical training 14 subjects were given atropine, propranolol, or both drugs simultaneously before and after a 5 weeks' physical training period. For a given ‘relative’ (per cent of maximum) submaximal oxygen uptake the activity of the autonomic nervous system was similar before and after the training. It is suggested that the training bradycardia in previously sedentary individuals after a short-term physical training period is due both to a reduced beta-adrenergic receptor activity and to an increased para-sympathetic activity.