Adolescents' personal beliefs about sufficient physical activity are more closely related to sleep and psychological functioning than self-reported physical activity: A prospective study

Background: Preliminary evidence among adults suggests that the ways in which individuals think about their physical activity (PA) behavior is more closely associated with their well-being than self-reported PA. This study therefore aimed to examine whether and how self-reported PA and personal beliefs about sufficient PA are associated with sleep and psychological functioning in a sample of Swiss adolescents, using both cross-sectional and prospective data. Methods: An overall sample of 864 vocational students (368 girls, 17.98 +/- 1.36 years, mean +/- SD) was followed prospectively over a 10-month period. At each measurement occasion, participants filled in a series of self-report questionnaires to assess their PA levels, their personal beliefs about whether or not they engage in sufficient PA, sleep (insomnia symptoms, sleep quality, sleep-onset latency, and number of awakenings), and psychological functioning (depressive symptoms, quality of life, perceived stress, and mental toughness). Results: Adolescents who believe that they are sufficiently physically active to maintain good health reported more restoring sleep. No differences in sleep were found between adolescents who meet PA recommendations vs. those who do not. Additionally, adolescents who believe that they were sufficiently physically active also reported better psychological functioning. This close relationship between adolescents' beliefs about their PA involvement and their sleep and psychological functioning was corroborated in the prospective analyses. Conclusion: Cognitive factors should be studied more intensively when elucidating the relationship among PA, sleep, and psychological functioning in young people, particularly when aiming to develop new exercise interventions targeting psychological outcomes. (C) 2019 Published by Elsevier B.V. on behalf of Shanghai University of Sport.