Does progressive supine exercise alter right ventricular volumes and ejection fraction in young male volunteers?
The increase in right ventricular stroke volume during supine exercise is driven by increased contractility rather than the Frank-Starling mechanism.
Right ventricular (RV) adaptation to supine exercise has been studied in 10 young male volunteers by 81mKr electrocardiogram (ECG)-gated radionuclide ventriculography. During progressive supine exercise, the ejection fraction gradually increased from a mean value of 46% at rest up to 60% at a maximal exercise level. End-diastolic volume however remained unchanged at a low exercise level and even slightly decreased at a higher exercise level. Little or no change in end-diastolic volume and an increase in ejection fraction produced a significant decrease in end-systolic volume and a net increase in stroke volume. These results indicate that the Frank-Starling mechanism does not contribute to the increase in right ventricular stroke volume during progressive supine exercise, but the increase in right ventricular stroke volume rather seems related to an increased contractility, presumably mediated by an increased sympathetic activity.
Mols et al. (Sun,) studied this question.