, Volume 25, Issue 3, pp 1025-1032
Date: 11 Oct 2013

A school-based resistance intervention improves skeletal growth in adolescent females

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Abstract

Summary

Twenty-two sixth-grade girls who participated in a 7-month school-based resistance-training program were compared to 22 controls. In a subanalysis of Tanner breast II (T2) and III (T3) subjects (n = 21 controls subjects (CON), n = 17 subjects in the high-intervention (INT)-dose group (HI)), T2 HI had greater narrow neck (NN) width gains than T2 CON (p < 0.05) and T3 HI had greater L3 bone mineral density (BMD) gains than T3 CON (p < 0.05).

Introduction

Physical activity modulates bone growth during adolescence, but an effective activity has not been identified for general use. The purpose of this study was to examine the effect of a school-based resistance-training program on skeletal growth in pre-menarcheal females.

Methods

Sixth-grade girls participated in a 7-month, resistance-training program (INT) embedded in physical education (PE) classes. Age- and maturity-matched CON from a neighboring school participated in the standard PE classes. INT dose defined high (HI) and low (LO) groups. At baseline (BL) and follow-up (FU), non-INT organized physical activity (PA, hours per week) and maturity status were recorded; DXA scans assessed total body, distal radius, proximal femur, and lumbar spine. Regression models analyzed growth in bone outcomes for HI versus CON, accounting for age, Tanner stage, height, and PA.

Results

Forty-four girls (22 HI, 22 CON) were 11.7 ± 0.3 years of age at BL; all were ≤6 months postmenarche and did not differ in bone growth over the course of the intervention (p > 0.05). However, in a subanalysis limited to subjects who were T2 or T3 at BL (n = 21 CON, n = 17 HI), T2 HI had greater gains in NN width (p = 0.01) compared to T2 CON, while T3 HI had greater gains in L3 BMD (p = 0.03) compared to T3 CON.

Conclusions

In a group of T2 and T3 sixth-grade girls, a school-based resistance-training intervention produced maturity-specific differential gains for HI versus CON at the hip and spine.