Download tone during exercise. The normal straight line relationships between

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ADAPTATION OF THE HEART TO EXERCISE
Investigations were carried out with the aid of a bicycle ergometer with
the aim of studying changes in heart rate, stroke volume and cardiac sympathetic
tone during exercise. The normal straight line relationships between work load,
cardiac output, heart rate and oxygen uptake were compared with those of
patients whose ventricular rates were controlled by artificial pacemakers.
When the ventricular rate was held constant the cardiac output increased with
the usual tachycardia. The oxygen uptake was shown to be independent of
heart rate but varied in the normal way with work load. Filling time and
ejection times were compared at low and high work loads in normal patients.
At low rates the major change in cycle time occurred in the filling period but
at high work loads there was a proportionately greater change in the ejection time.
The rate of flow of blood into the ventricles during diastole was shown to be
directly related to the work load. By means of the beta sympathetic blocking
drug Propranolol it was shown that the effect of increased sympathetic tone on
exercise is to increase the rate, decrease the stroke volume and increase the
rate of ejection of blood from the ventricles.
Dr. E. Sowton
-2-
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"Adaptation of the Heart to Exercise"
E. Sowton
Bull Br Assoc Sport Med 1965 2: 2
doi: 10.1136/bjsm.2.1.2
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