Purpose. Although the family environment is a potentially important influence on children's physical activity (PA), prospective data investigating these associations are lacking. This study aimed to examine the longitudinal relationship between the family environment and PA among youth. Design. A 5-year prospective cohort study. Setting. Nineteen randomly selected public schools in Melbourne, Australia. Subjects. Families of 5- to 6-year-old (n = 190) and 10- to 12-year-old (n = 350) children. Measures. In 2001, parents reported their participation in PA, family-based PA, and support and reinforcement for their child's PA. In 2001, 2004, and 2006, moderate to vigorous intensity PA (MVPA) was assessed among youth using accelerometers. Weekend and "critical window" (after school until 6:00 P.M.) MVPA were examined because we hypothesized that the family environment would most likely influence these behaviors. Analysis. Generalized estimating equations predicted average change in MVPA over 5 years from baseline family environment factors. Results. Maternal role modeling was positively associated with boys' critical window and weekend (younger boys) MVPA. Paternal reinforcement of PA was positively associated with critical window and weekend MVPA among all boys, and paternal direct support was positively associated with weekend MVPA (older boys). Among girls, maternal coparticipation in PA predicted critical window MVPA, and sibling coparticipation in PA was directly associated with weekend MVPA (younger girls). Conclusions. Longitudinal relationships, although weak in magnitude, were observed between the family environment and MVPA among youth. Interventions promoting maternal role modeling, paternal reinforcement of and support for PA, and Maternal and sibling coparticipation in PA with youth are warranted
Objective. To examine associations between family physical activity and sedentary environment and changes in body mass index (BMI) z-scores among 10-12-year-old children over three years. Method. Design. Longitudinal (three-year follow-up). Subjects. In total, 152 boys and 192 girls aged 10-12 years at baseline. Measurements. Measured height and weight at baseline and follow-up (weight status, BMI z-scores); aspects of the family physical activity and sedentary environment (parental and sibling modelling, reinforcement, social support, family-related barriers, rules/restrictions, home physical environment) measured with a questionnaire completed by parents at baseline. Results. At baseline, 29.6% of boys and 21.9% of girls were overweight or obese, and mean (standard deviation, SD) BMI z-scores were 0.44 (0.99) and 0.28 (0.89), respectively. There was a significant change in BMI z-score among girls (mean change=0.19, SD=0.55, p < 0.001), but not boys. Among boys, the number of items at home able to be used for sedentary behaviour (B=0.11, p=0.037) was associated with relatively greater increases in BMI z-score. Among girls, sibling engagement in physical activity at least three times/wk (B=-0.17, p=0.010) and the number of physical activity equipment items at home (B=-0.05, p=0.018) were associated with relatively greater decreases in BMI z-score. Conclusion. Sibling physical activity and environmental stimuli for sedentary behaviours and physical activity within the home may be important targets for prevention of weight gain during the transition from childhood to adolescence.