Objectively measured physical activity, body composition and physical fitness: Cross‐sectional associations in 9‐ to 15‐year‐old children

Abstract

The aim of this study was to examine and quantify the cross-sectional associations of body composition (BC), physical activity (PA) and sedentary time (ST) with physical fitness (PF) in children and adolescents. A sample of 594 Finnish students (56% girls), aged 9-15 (12.4 ± 1.3 years) were selected for a study performed in 2013. The measurements of the Move! monitoring system for physical functional capacity were used to measure cardiorespiratory and musculoskeletal fitness and fundamental movement skills. Moderate-to-vigorous PA (MVPA) and ST were measured objectively with an accelerometer and BC by a bioelectrical impedance analysis. Fat mass index (FMI) and fat-free mass index (FFMI) were calculated to represent height-adjusted BC. Associations were explored with a linear regression model. In general, FMI had statistically significant negative associations, while FFMI and MVPA had positive associations with PF. No statistically significant associations were observed between ST and PF. In general, FMI had the strongest association with PF, although some variation occurred with sex and PF component. However, associations were practically relevant only in 20-m shuttle run, push-up, curl-up and 5-leaps test. For example, approximately 5 kg increase in fat mass in 155 cm tall children was estimated to correspond to 8 laps in 20-m shuttle run. Similar increase in fat-free mass corresponded to +4 and +6 laps, and 10 min increase in daily MVPA +3 and +2 laps in 20-m shuttle run, in boys and girls, respectively. Understanding these associations is necessary when interpreting children's PF and designing interventions.

Physical activity, aerobic fitness and brain white matter: their role for executive functions in adolescence

“…Participants .2 years old) for this cross-sectional study were recruited from a larger follow-up study (for more details, see Joensuu et al [2018]). Sixty-one right-handed subjects participated in the brain magnetic resonance imaging (MRI) experiments, of which two participants did not complete the diffusion-weighted imaging protocol.…”

“…The physical activity was objectively measured using the triaxial ActiGraph GT3X+ and wGT3X+ accelerometers (Pensacola, FL, USA; for full details, see Joensuu et al [2018]). The participants were instructed to wear these devices on their right hip during waking hours for seven consecutive days (except during bathing and swimming).…”

“…The maximal 20-m shuttle run test was employed to assess the aerobic fitness of the participants. The test was performed as described by Nupponen et al (1999) and specified in detail for the present data collection in Joensuu et al (2018). Each participant ran between two lines, 20 metres apart, at an accelerating pace, which was indicated with an audio signal.…”

Physical activity is positively related to local functional connectivity in adolescents’ brains

“…Participants (12.7-16.2 years old) were recruited from a larger follow-up study (Joensuu et al, 2018;Syväoja et al, 2019). A total of 61 right-handed subjects participated in the magnetic resonance imaging (MRI) scan (for participant demographics see, Table 1).…”

“…Physical activity was objectively measured using the triaxial ActiGraph GT3X+ and wGT3X+ accelerometers (Pensacola, FL, USA; for full details, see Joensuu et al, 2018). The participants were instructed to wear these devices on their right hips during waking hours for seven consecutive days (except during bathing and swimming).…”