and Objectives Physical activity has a great influence on children's health and cognition. Working memory, a key aspect of cognitive function, is heavily implicated in classroom activities. As cognitive function improves in younger ages, identifying a relationship between physical activity and working memory would be beneficial to the child population. The objective of the study was to describe physical activity level and working memory capacity and to determine their relationship in

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... old children. Methods A cross sectional study was done involving 180 (90 boys) 10-11-year-old children randomly selected from six schools in Colombo, Sri Lanka. A physical activity questionnaire for children (PAQ-C) was used to assess the physical activity level. A wall mounted stadiometer and an electronic weighing scale were used to assess height and weight. To assess verbal and nonverbal components of working memory, the digit span test (forward and backward) and Corsi block tapping test (forward and backward) were used. Ethics clearance was obtained from the Faculty of Medicine, University of Colombo. Data was analyzed using the independent sample t test, Pearson correlation test and one way ANOVA test on SPSS version 25. Results Mean PAQ-C score and mean scores for digit span tests and Corsi block tapping forward test were significantly higher in boys compared to girls (p<0.05). Positive correlations were found between physical activity level and digit span forward test (r=0.49; p<0.01), Corsi block tapping forward test (r = 0.31; p<0.01) and Corsi block tapping backward test (r=0.52; p<001). Conclusions Increased physical activity levels lead to increase in working memory capacity. Sex difference was observed in physical activity level and working memory capacity where boys outperformed girls.