[Investigations of the working capacity of children 7 to 10 years old (author's transl)].

The investigations performed have aimed at explaining how the adaptation of the cardiovascular system to exertion occurs in 7 to 10 years old children, and whatthe level of working capacity in this age group is in girls and boys, and also what relationship there is between the level of working capacity and such morphological parameters as body weight, body height and body surface area, and to elucidate whether systematic swimming, instead of traditional physical education lessons, exerts an influence on the level of working capacity of children in this age group. All 7 to 10 years old female and male pupils of the Primary School No. 183 in Warsaw were examined. In total 131 children were examined, among them 67 boys and 64 girls. Only healthy children were examined. The examinations were carried out in the school premises from November 1971 to February 1972. 30 boys were examined with greater accuracy at the Academy of Medicine. The examinations were carried out on ergometer bicycle assessing the adaptation to exertion and physical work capacity during three various submaximal exercises. The working time during each exercise depended on the achievement of a steady state and lasted 6-8 minute on average. The magnitude of the load burden was ajusted individually for every child according to its working capacity. The adaptation of the cardiovascular system to exertion was assessed by virtue of the analysis of the course of the changes in heart rate and the arterial blood pressure. The adaptation of the respiratory system to exertion was assessed by virtue of measuring the number of respirations, minute lung ventilation and the respiratory quotient, determined during three submaximal exercises in an open system. Physical working capacity was determined according to Sjostrand-Wahlund's method (PWC170). In all children examined the changes in the cardiovascular system during work were linear. To the same amount of work the boys reacted by a lower heart rate than girls. The children responded to the work performed by a low increase in systolic pressure and a small decrease of diastolic pressure. In the fifth minute of the rest after work the heart rate resumed rest values or was lower than these values. At the same time the systolic arterial pressure resumed the initial state, but a slight decrease of the diastolic pressure was maintained for over five minutes of rest.