Relationship between health-related quality of life and physical fitness in Norwegian adolescents.

AIMS: This cross-sectional study investigated the association between health-related quality of life (HRQoL), cardiorespiratory fitness (CRF) and muscular fitness in 14-year-old adolescents. METHODS: Norwegian adolescents (N = 1985) carried out a 10-min running test to assess cardiorespiratory fitness and three different muscular fitness tests (handgrip, sit-ups, and standing broad jump) and answered the KIDSCREEN-27 questionnaire to provide HRQoL data. Linear-mixed effect models were applied to detect relationships among the variables. RESULTS: Running-test results were positively associated with higher scores in the following KIDSCREEN domains: physical well-being, psychological well-being, autonomy and parent relationships, and school environment (ß = 0.01-0.04; p < .01 for all). Performance in sit-ups test was positively associated with higher scores in three out of five KIDSCREEN domains: physical well-being (ß = 0.31; p < .001), social support and peers (ß = 0.16; p = .023), and school environment scores (ß = 0.19; p = .006). An inverse association was found between the handgrip test results and the score on psychological well-being domain (ß = - 0.10; p = .013). CONCLUSIONS: The associations between HRQoL and physical fitness were trivial (abdominal strength and handgrip strength) to small (CRF) but confirmed that earlier findings from children also are applied to adolescents. Explosive strength in the lower body showed no association with HRQoL. Further research should investigate the direction of causality. TRIAL REGISTRATION: Clinicaltrials.gov ID nr: NCT03817047. Registered 01/25/2019 'retrospectively registered'.

The association between physical fitness and mental health in Norwegian adolescents.

BACKGROUND: Studies 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. METHODS: Adolescents 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). RESULTS: Body 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. CONCLUSIONS: There 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 REGISTRATION: The study is registered in ClinicalTrials.gov ID nr: NCT03817047. Retrospectively registered January 25, 2019.