Abstract
BackgroundStudies indicate that health-related components of physical fitness are associated with mental health outcomes. 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 whether body composition, muscular strength and cardiorespiratory fitness were associated with self-reported mental health in Norwegian adolescents.MethodsAdolescents from four regions of Norway (n = 1486; mean age = 13.9; girls = 50.6%) participated. Self-reported mental health (psychological difficulties) was measured by completing the Strengths and Difficulties Questionnaire. Cardiorespiratory fitness was assessed with an intermittent running test; muscular strength was assessed by measuring handgrip strength, standing broad jump and sit-ups; and body composition was assessed by calculating body mass index from weight and height. Linear mixed effects models were conducted to assess the associations between the health-related components of physical fitness and psychological difficulties. School clusters were included as random effects and all models were controlled for sex, socioeconomic status and birthplace (domestic or foreign).ResultsBody composition was not associated with psychological difficulties. Muscular strength was independently associated with psychological difficulties, but when all independent variables were entered in the fully adjusted model, only cardiorespiratory fitness was associated with psychological difficulties.ConclusionsThere was a small but significant inverse association between cardiorespiratory fitness and levels of psychological difficulties in Norwegian adolescents. The results suggest that muscular strength is not associated with psychological difficulties in adolescents, when controlling for cardiorespiratory fitness. Future research should focus on the prospective association between physical fitness components and mental health outcomes in adolescents.Trial registrationThe study is registered in ClinicalTrials.gov ID nr: NCT03817047. Retrospectively registered January 25, 2019.
Highlights
Studies indicate that health-related components of physical fitness are associated with mental health outcomes
We report estimates and their 95% confidence intervals
Model 1 indicated no association between body mass index (BMI) and total difficulties score (TDS)
Summary
Design and participants The present study used cross-sectional data from the baseline tests of the School in Motion project [33]. Mental health To measure mental health, the participants completed a Norwegian language version of the Strengths and Difficulties Questionnaire [SDQ [36];]. TDS scores from 0 to 40 and is a dimensional measure of mental health for children and adolescents, which means that on a population level, there is a detectable reduction in psychopathology for each point-reduction on the scale [37]. In models one to six, we assessed the separate associations between TDS and the muscular strength variables and the health-related fitness components. A linear mixed effects model was conducted on the imputed dataset, with TDS as the dependent variable, and all health-related components of physical fitness variables and covariates entered as independent variables. The imputed dataset results are presented, in addition to the complete-case results, as recommended by Manly and Wells [50] and Sterne et al [51]
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