Original Articles
A school-based exercise intervention augments bone mineral accrual in early pubertal girls,☆☆

https://doi.org/10.1067/mpd.2001.118190Get rights and content

Abstract

Objective: To evaluate the effects of an elementary school-based physical education exercise intervention program on bone mineral accrual in prepubertal and early pubertal girls. Study design: A total of 14 schools were randomly assigned to control (C) and intervention (I) groups. Girls in the I group completed a 10-minute, 3 times per week circuit of varied jumping activities over 7 months. We measured total body, lumbar spine, proximal femur, femoral neck, and trochanteric bone mineral content and areal bone mineral density and estimated femoral neck volumetric bone mineral density at baseline and final measurement in 87 girls in the I group and 90 girls in the C group. Girls were between 8.7 and 11.7 years at baseline. Tanner stage 1 girls were considered prepubertal; Tanner stages 2 and 3 girls were considered early pubertal. We used analysis of covariance (adjusting for baseline bone values, change in size, age, and maturity) to compare 7-month change in bone mineral content, areal bone mineral density, and volumetric bone mineral density between C and I groups within prepubertal and early pubertal girls. Results: There was no difference in 7-month change in bone parameters between prepubertal I and C groups. Early pubertal girls in the I group gained 1.5% to 3.1% more bone at the femoral neck and lumbar spine than early pubertal girls in the C group (P < .05); gain at other sites did not differ. Conclusions: In girls, early puberty may be a particularly opportune time during growth for simple exercise interventions to have a positive effect on bone health. (J Pediatr 2001;139:501-8)

Section snippets

Design

This study was a randomized, prospective, school-based intervention that included 7 intervention and 7 control elementary schools. Baseline measurements were made during the fall of the school year (September to October); the intervention was completed from late October to late May (7 months in duration); and final measurements were made at the end of the school year (June).

Subjects

We recruited principals, teachers, and students from Richmond, a multi-ethnic school district outside of Vancouver,

Subjects

A total of 8 girls attending a control school changed schools, and 6 girls attending an intervention school did not return for follow-up measures (1 lost interest, 5 changed schools). Thus, prospective data were available for 26 PRE girls in the C group and 44 PRE girls in the I group and 64 EARLY girls in the C group and 43 EARLY girls in the I group (N = 177).

Classes at intervention schools performed the circuit intervention a mean of 57 times (SD, 10) over the school year. We estimated that

Discussion

This prospective intervention study showed a maturity-related, region-specific bone response to weight-bearing exercise in prepubertal and early pubertal girls. This has important practical implications for school physical education programs. Girls who were early pubertal at the start of the exercise intervention program gained significantly more bone at the FN and LS than their maturity-matched, nonparticipating counterparts. In contrast, the exercise intervention did not promote bone gain in

Acknowledgements

We thank the grades 4, 5, and 6 students, teachers, and principals in the Richmond School District who volunteered their time and resources for this study.

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    Supported by the British Columbia Health Research Foundation (No. 2400-2, 10898-2).

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    Reprint requests: Heather McKay, PhD, School of Human Kinetics, 6081 University Blvd, Vancouver, British Columbia, V6R 1N6, Canada.

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