Associations between health-related quality of life, cardiorespiratory fitness, muscle strength, physical activity and waist circumference in 10-year-old children: the ASK study.

PURPOSE: To examine the associations between cardiorespiratory fitness, muscle strength, physical activity and waist circumference with self-reported health-related quality of life (HRQoL) in children.
METHODS: We conducted a cross-sectional analysis that included 1129 school children aged 10 years from 57 schools in Sogn and Fjordane County, Norway. The HRQoL outcome was assessed by the self-reported KIDSCREEN-27 questionnaire, which covers five life domains. Independent variables were cardiorespiratory fitness assessed by the Andersen intermittent field running test, handgrip strength measured by a hand dynamometer, explosive strength in the lower body using a standing broad jump test, physical activity (counts per minute) using an accelerometer and abdominal adiposity measured by waist circumference. Statistical analyses were performed using linear mixed-effect models including school site as a random effect. Age and sex were entered as covariates.
RESULTS: Only cardiorespiratory fitness was positively associated with higher scores on all five KIDSCREEN-27 domains (P < 0.047 for all). Explosive strength in the lower body was positively associated with higher autonomy and parents scores (P = 0.018), while physical activity was positively associated with higher physical well-being scores (P = 0.008).
CONCLUSIONS: Improving cardiorespiratory fitness might be especially useful for improving HRQoL in children.