ABSTRACT
Despite the large number of studies of young people’s aerobic power data on the physiological mechanisms that essentially determine maximal oxygen uptake ( https://www.w3.org/1998/Math/MathML"> V ˙ O 2 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315025001/ca0a1b50-16e7-4532-9e85-fe2cd38f2327/content/inline-eqn625_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> max) are sparse. Concerning the prepubertal growth period, only one study appears to yield a detailed analysis of the most important mechanisms such as central haemodynamics[1] and pulmonary gas exchange[2] including diffusing capacity[3] at rest and during submaximal and maximal exercise. The authors studied 9 boys aged 11-13 y using invasive methods at rest both in the supine and seated position, but only in the seated posture during exercise. The study thus does not allow any conclusion as to the effect of body position on the haemodynamic response to exercise. Concerning the adjustment of left ventricular (LV) contractility in relation to haemodynamic changes and to different body positions no information at all seems available. The purpose of the present study was to provide more detailed insight into the effects of body position on cardiovascular adaptation by comparing the adjustment of haemodynamics and of LV contractility at rest and during exercise in the supine versus seated posture.
