The association between mental health and physical fitness in Norwegian adolescents
Abstract Background: Studies indicate that cardiorespiratory fitness, muscular strength and body composition are associated with mental health. However, research is scarce concerning this relationship in young adolescents in general and non-existent in Norwegian populations specifically. The aim of the study was to examine the relationship between different health-related aspects of physical fitness and self-reported mental health in Norwegian adolescents. Methods: Participants from four regions of Norway (n = 1486; mean age = 13.9; girls = 50.6%) completed the Strengths and Difficulties Questionnaire, and were measured for cardiorespiratory fitness, muscular strength and body composition. Linear mixed effects models were conducted to assess the associations between the health-related aspects of physical fitness and the total difficulties score of the questionnaire. Results: Body composition was not associated with total difficulties score. Muscular strength independently was associated with total difficulties score, but when all independent variables were entered in the fully adjusted model, only cardiorespiratory fitness was associated with total difficulties score. School clusters were included as random effects and all models were controlled for sex, socioeconomic status and birthplace (domestic or foreign). Conclusions: A small but significant negative association between cardiorespiratory fitness and total difficulties score indicated that higher cardiorespiratory fitness predicted better mental health in Norwegian adolescents. The results suggest that muscular strength is not associated with mental health in adolescents, when controlling for cardiorespiratory fitness. Future research on how exercise affects mental health should investigate whether there is a greater effect for participants who improve their cardiorespiratory fitness.