In modern times, it can often be noticed that children spend more time in front of screens, and less time in nature, playing with their peers or in other activities that do not include modern technology such as cell phones or computer games. An increasingly prevalent sedentary lifestyle and time spent in front of screens is a potential health risk. The previous research presented in this paper attaches great importance to children's physical activity and shows that physical activity has a positive effect on children's functional abilities. The transformation of functional abilities belongs to the sphere of the most useful and most frequently applied transformations of the training process, namely the one aimed at increasing the efficiency of the cardiovascular and cardiorespiratory systems, that is, at the comprehensive increase of aerobic and anaerobic capacities. In this final paper, research was conducted in a kindergarten in Novi Zagreb, which shows that the girls and boys aged 5 and 6 who participated in the research are in good condition, and their cardio-respiratory system is within the accepted standards for children of that age. The research has shown that boys and girls at the mentioned age equally show aerobic capacities, abilities, and acceptable aerobic endurance for that age.