Cardiorespiratory fitness, muscular fitness and mental health in older adolescents: A multi-level cross-sectional analysis.

Physical activity interventions that promote cardiorespiratory (CRF) and muscular fitness (MF) may improve mental health in young adolescents. However, less is known about the links between fitness and mental health in older adolescents, as they are an understudied population. In addition, the association between MF and adolescents' mental health is less clear than it is for CRF. Our primary aim was to investigate whether MF is independently associated with mental health in a sample of older adolescents. Our secondary aim was to determine if the association between fitness and mental health was moderated by sex, socio-economic status (SES) or weight status. Participants were 670 students (16.0 [0.4] years, 44.6% female) from 20 secondary schools in New South Wales, Australia. Mental health (well-being and internalizing problems) was self-reported using the Short Warwick-Edinburgh Mental Wellbeing Scale and the Strengths and Difficulties Questionnaire. We assessed CRF using the Progressive Aerobic Cardiovascular Endurance Run and MF using the push-up and standing long jump tests. After controlling for CRF, MF was not associated with mental health. CRF was associated with well-being (β = 0.20, p < .001) and internalizing problems (β = -0.27, p < .001). The strength of association between CRF and mental health was stronger in girls, than boys. No interaction effects were observed for SES or weight status. Although cross-sectional, our findings provide further evidence of the potential benefits of CRF for adolescents' mental health (i.e., well-being and internalizing problems), particularly girls. However, MF may be less relevant for mental health among this population.