Use of the Frank-Starling mechanism during submaximal versus maximal upright exercise.
To evaluate the extent to which the Frank-Starling mechanism is utilized during successive stages of vigorous upright exercise, absolute left ventricular end-diastolic volume and ejection fraction were determined by gated blood pool scintigraphy at rest and during multilevel maximal upright bicycle exercise in 30 normal males aged 26-50 yr, who were able to exercise to 125 W or greater. Left ventricular end-systolic volume, stroke volume, and cardiac output were calculated at rest and during each successive 3-min stage of exercise [25, 50, 75, 100, and 125-225 W (peak)]. During early exercise (25 W), end-diastolic and stroke volumes increased (+17 +/- 1 and +31 +/- 4%, respectively), with no change in end-systolic volume. With further exercise (50-75 W) end-diastolic volume remained unchanged as end-systolic volume decreased (-12 +/- 4 and -24 + 5%, respectively). At peak exercise end-diastolic volume decreased to resting level, stroke volume remained at a plateau, and end-systolic volume further decreased (-48 +/- 7%). Thus the Frank-Starling mechanism is used early in exercise, perhaps because of a delay in sympathetic mobilization, and does not appear to play a role in the later stages of vigorous exercise.
D000328:Adult; D001794:Blood Pressure; D002302:Cardiac Output; D005080:Exercise Test; D006321:Heart / Q000502:physiology*; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D005082:Physical Exertion; D011187:Posture; D013318:Stroke Volume