Gas Transport Capacity And Cardiorespiratory Function In 9 To 15 Year Old Boys During Exercise In Relation To Growth, Maturation, Heart Size And Regular Physical Activity

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The purpose of the four experiments which comprised this thesis was to describe the development of gas transport capacity and cardiorespiratory function during exercise as a function of body size, growth, physical activity and heart size in boys between 9 and 15 years of age.;A cross-sectional design incorporating three groups of 39 boys each, between 9.5 to 11.5, 11.6 to 13.5 and 13.6 to 15.5 years of age was used in the first two experiments. There was equal representation of active and inactive boys (as determined by questionnaire) within each age group. These experiments described (1) the relationship between maximal gas transport capacity as measured by aerobic power (VO(,2)(' )max) and echocardiographically determined measurements of resting cardiac size, (2) the relative contribution of body size, physical activity and selected measurements of cardiac size in determining VO(,2)(' )max and stroke volume (SV submax) during heavy intensity submaximal exercise and (3) the relative contribution of stroke volume and arterio-venous oxygen difference (Ca-vO(,2) diff) in determining exercise oxygen uptake (VO(,2)(' )submax) in boys at different stages of development between 9 and 15 years of age.;VO(,2)(' )max was measured during treadmill exercise, heart size was studied by M-mode echocardiography during supine rest, and level of physical activity was assessed by questionnaire. Submaximal oxygen uptake (VO(,2)(' )submax) and cardiac output (Q)(' )were determined by the open circuit and indirect Fick (CO(,2)) rebreathe techniques respectively, at three submaximal work rates during cycle ergometer exercise and interpolated to a heart rate of 155 beats.min('-1). SV and Ca-vO(,2) diff were determined by solution of the Fick equation at each level of exercise and were also interpolated to a heart rate of 155 beats.min('-1). . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of school.) UMI

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