Haemodynamic responses to the dynamic exercise in subjects exposed to different gravitational conditions.
Different types of adaptation of the cardiovascular system to the gravitational forces (hypokinetic and hyperkinetic) have been described in the healthy and the sick subjects under resting conditions. The aim of the present study was to elucidate whether haemodynamic responses to the dynamic exercise performed under various gravitational conditions are determined by the type of adaptation of the cardiovascular system to the gravitational forces at rest. The study was performed on 249 healthy men, 20-60 years old. To assess the type of regulation of the cardiovascular system arterial blood pressure (MABP), heart rate (HR), stroke volume (SV), cardiac output (CO), and systolic function (SF) of the heart were determined in each subject at rest in the upright (orthostatic state) and in the supine position. Subsequently, the subjects were performing exercise on a cycloergometer in the sitting and the supine position. Four gradually increasing workloads were applied. Measurements of HR, MABP, SV, CO, and SF were repeated at the end of each workload. SV, CO and SF were determined by means of rheography. The results revealed that in the individuals showing at rest the hypokinetic type of orthostatic cardiovascular adaptation the augmentation of CO during exercise in the sitting position was caused by significant increases of HR and SV. In contrast, the subjects with the hyperkinetic type of orthostatic adaptation the increase in CO during exercise in the sitting position was much smaller and resulted predominantly from acceleration of HR. It is concluded that the cardiovascular adaptation to the dynamic exercise depends not only on the position of the body in which the exercise is performed but it is also determined by the type of adaptation of the cardiovascular system to the gravitational forces at rest. In the sitting position the pumping capacity of the heart is significantly greater in the hypokinetic than in the hyperkinetic type of the cardiovascular regulation; this relationship being reversed during exercise in the horizontal position.
Puchalska
L
L
Department of Experimental and Clinical Physiology, Medical University of Warsaw, Poland. puhalski@gmail.com
Belkania
G S
GS
D000222:Adaptation, Physiological; D000328:Adult; D001794:Blood Pressure; D002302:Cardiac Output; D005080:Exercise Test; D006112:Gravitation; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D007024:Hypotension, Orthostatic / Q000209:etiology; D008297:Male; D008875:Middle Aged; D010992:Plethysmography, Impedance; D011187:Posture / Q000502:physiology*; D012146:Rest / Q000502:physiology; D013318:Stroke Volume; D016683:Supine Position / Q000502:physiology