Progressive cycle exercise in normal children produced an initial rise in stroke volume that plateaued at mild-moderate intensities, maintained by increasing heart rate and contractility.
Observational (n=39)
How do stroke volume and cardiac output respond to progressive exercise in normal children?
In normal children, stroke volume increases initially during exercise and plateaus at mild-moderate intensities, maintained at higher workloads by increased heart rate and contractility.
UNLABELLED: The cardiac responses to exercise are influenced by a complex interplay of changes in diastolic filling, intrinsic myocardial contractility, heart rate, and ventricular afterload. PURPOSE: To characterize these responses in children, findings are reported from two studies utilizing Doppler echocardiographic assessment of stroke volume and cardiac output during maximal upright and semisupine cycle exercise. METHODS: In study 1, stroke volume, heart rate, and peak aortic velocity were assessed during upright cycle exercise to exhaustion in 39 sixth-grade boys. In study 2, similar methods were used to examine cardiac responses to semisupine exercise with measurement of left ventricular dimensions by two-dimensional echocardiography. RESULTS: The findings support patterns similar to that previously described in adults, with an initial rise in stroke volume reaching a plateau at mild-moderate exercise intensities. CONCLUSIONS: The observations in these two studies also suggest 1) peripheral vasodilatation plays an important role in the early rise in stroke volume, 2) increasing heart rate acts to maintain a stable stroke volume and left ventricular diastolic dimension at high workloads, and 3) improvements in contractility serve to maintain stroke volume as the systolic ejection period shortens.
Rowland et al. (Tue,) conducted a observational in Normal children (n=39). Progressive cycle exercise (upright and semisupine) was evaluated on Stroke volume, heart rate, peak aortic velocity, and left ventricular dimensions. Progressive cycle exercise in normal children produced an initial rise in stroke volume that plateaued at mild-moderate intensities, maintained by increasing heart rate and contractility.