Associations between objectively assessed components of physical activity and health-related fitness in 10- to 14-year-old children

Background: Our aim was to investigate the association between different components of physical activity (PA) and health-related fitness in 10-to 14-year-old children. Methods: 241 children were recruited from 15 primary and 15 secondary schools. PA was assessed using the SenseWear Mini and an electronic diary. Health-related fitness was assessed using Eurofit and translated into indicators of body fatness, cardiorespiratory fitness and muscular fitness. Associations between PA intensity and physical fitness components were determined using multiple linear regression models adjusted for possible confounders and the contribution of PA domains per intensity categories was calculated. Results: Associations between PA intensities and body fatness were low to moderate (|β| = 0.09 to 0.44), explaining up to 6% of the variance in boys and 17% in girls. For cardiorespiratory fitness, associations were higher (|β| = 0.17 to 0.56), with PA explaining up to 6% of the variance in boys and 31% in girls. Low-tomoderate associations (|β| = 0.06 to 0.43) were found for muscular fitness, with PA explaining up to 7% in boys and 13% in girls. Stronger associations were found for sedentary and light activities. Conclusions: Low-to-moderate associations between PA and fitness components were observed, with higher associations in girls. Sedentary and light intensity activity showed the strongest link with body fatness, cardiorespiratory fitness and muscular fitness.