Purpose: To test effects of parent/child training designed to increase calcium intake, bone-loading physical activity (PA), and bone density.
Design: Two-group randomized controlled trial.
Setting: Family-based intervention delivered at research center.
Subjects: 117 healthy children aged 10-13 years (58.1% female, 42.7% Hispanic, 40.2% White). Ninety-seven percent of participants had at least one parent graduate from high school and 37.2 % had at least one parent graduate from a 4-year university.
Intervention: Children and parents were randomly assigned to diet and exercise (experimental) or injury prevention (control) interventions. Children were taught in eight weekly classes how to engage in bone-loading PA and eat calcium-rich foods or avoid injuries. Parents were taught behavior management techniques to modify children's behaviors.
Measures: Measures at baseline and at 3, 9, and 12 months included 24-hour diet and PA recalls, and bone mineral density (BMD) by dual-energy x-ray absorptiometry.
Analysis: Analysis of variance and generalized estimating equations (GEE) assessed group by time differences. Comparisons were conducted separately for boys and girls.
Results: For boys, cross-sectional differences between experimental and control groups were achieved for 3- and 9-month calcium intake (1352 vs. 1052 mg/day, 1298 vs. 970 mg/day, p < .05). For girls, marginal cross-sectional differences were achieved for high-impact PA at 12 months (p < .10). For calcium intake, a significant group by time interaction was observed from pretest to posttest for the full sample (p = .008) and for girls (p = .006) but not for boys. No significant group by time differences in calcium were observed across the follow-up period. No group by time differences were observed for high-impact PA. Among boys, longitudinal group by time differences reached significance for total hip BMD (p = .045) and femoral neck BMD (p = .033), even after adjusting for skeletal growth. Similar differential increases were observed among boys for bone mineral content (BMC) at the hip (p = .068) and total body (p = .054) regions. No significant group by time interaction effects were observed for girls at any bone site for BMD. For BMC, control girls showed a significant increase (p = .03) in spine BMC compared to intervention girls.
Conclusion: This study demonstrated that parent/preteen training can increase calcium intake and attenuate the decline in high-impact PA. Results suggest that more powerful interventions are needed to increase activity levels and maximize bone mineral accrual during preadolescent years.