(1) Background: Both physical activity and sleepiness were found to influence the development of executive functioning. The present study aimed to address the effects of different levels of physical activity on adolescents' executive performance (i.e., working memory and inhibition), and the role of sleepiness in this relationship. It was hypothesized that a higher level of physical activity would be associated with better executive functioning, while this relationship was mediated (at least partially) by reduced sleepiness at school. (2) Methods: 212 adolescents aged from 10 to 17 were recruited, and they were requested to wear accelerometers for seven consecutive days to measure daily levels of physical activity. The Cleveland Adolescent Sleepiness questionnaire (CASQ) was used to assess sleepiness. The working memory and inhibition control were assessed to indicate executive functioning. (3) Results: It was found that sedentary activity was negatively associated with working memory performance, while light and moderate-to-vigorous physical activities were related to better working memory. The relationship between different levels of physical activity and working memory was mediated by reduced sleepiness at school. (4) Conclusions: Our findings provide nuanced evidence that the benefits of light and moderate-to-vigorous physical activity on cognitive development could be explained by reduced sleepiness at school.
Keywords: adolescents; cognitive functions; physical activity; sleepiness.