The aim of this research was twofold: a) the examination of the relations between the construct of self-concept (sport competence and physical self) and the criterion (volume of physical activity and intensity of physical activity) in physical education classes for preadolescents and b) the examination of the contribution of the variables of self-concept to the predictions of the variance criterion, thus the partial influence of predictor variables in the prediction of physical activities of students in late childhood. The following instruments were used on the relevant sample of participants from Valjevo (N=212) whose average age was 12.5 years: self-perception of the self-concept questionnaire (SPPC), pedometer (CoachGear) and heart rate monitor (Suunto memory belt) for measuring the volume and intensity of the physical activity. The internal consistency coefficient of the SPPC questionnaire was (α=.82) for sport competence and (α=.85) for the physical self, which indicated the satisfactory reliability and its applicability of the Serbian preadolescent population. Using the Pearson correlation coefficient, with a probability of 99%, the low statistically relevant positive linear correlation between the examined variables was determined. Using the model of multiple linear regression analysis, it was determined that the construct of self-concept explains 19% of the perceived volume of physical activity variance and 20% of the intensity of the physical activity variability for the relevance threshold (p≤.01). The results of the regression equation indicated that the independent variable Sport Competence explained the variance in the Volume of physical activity and the Intensity of physical activity variables with preadolescents (β=.32, β=.30) in a statistically significant manner, while the variable Physical self was not a statistically significant partial predictor of any of the criteria. The obtained empirical findings are in accordance with the results of the previous studies, and there was a discussion about the theoretical and practical implications of the obtained findings
