Stroke volume dynamics during progressive exercise in healthy adolescents.

Understanding cardiac responses to exercise in healthy subjects is important in the evaluation of youth with heart disease. This review article incorporates previously published original research from the authors' laboratory to examine changes in stroke volume during progressive exercise which are consistent with a model in which circulatory responses are controlled by alterations in the systemic vascular resistance. Stroke volume dynamics and cardiovascular responses to a progressive upright cycle test were examined in three groups of healthy, untrained adolescent subjects. These indicated a) a progressive decease in systemic vascular resistance, b) little change in stroke volume after an initial rise related to orthostatic changes in ventricular refilling, c) evidence of a constant or slightly declining left ventricular end diastolic filling pressure, d) and increases in markers of ventricular contractility. These observations are consistent with peripheral (vascular resistance) rather than central (cardiac) control of circulation with exercise. Changes in stroke volume during exercise need to be interpreted in respect to alterations in heart rate and myocardial functional capacity.