Effects of daily physical activity on bone densuity in pre-and peripubertal girls

Introduction

Childhood and adolescence are considered to be the prime time for maximizing one´s genetically-determined peak bone mass through modification of life-style/environmental factors1. Physical activity (PA) plays an important role in regulation of bone development and maintenance2. Previous study has shown that the anabolic effect of PA was stronger if the activity began prior to rather than after the onset of menarche3. The purpose of the present study was to evaluate the impact of daily PA on bone development in pre- and peripubertal girls.

Methods

The subjects comprised 220 healthy Chinese girls, aged 10-12 years with Tanner Stage I and II maturational status, and no history of serious medical conditions or medication known to affect bone metabolism.
PA was assessed by a self-administrated questionnaire designed to evaluate the type, intensity, frequency, and duration of PA during past six months. A equation used to determine the scores of PA . According to their scores of PA, the girls were divided into three groups: low, moderate, and high PA group.
QUS-2 (Quantitative Ultrasound) was used to measure the density at the heel.
One-way analysis of variance (ANOVA) followed by least significant difference (LSD) was used to compare the differences among the three PA groups. If significant difference was found in weight or height between groups, analysis of covariance (ANCOVA) was used. A p-value of less than 0.05 was considered statistically significant.

Results

There were 121 girls at Tanner Stage I and 99 girls at Tanner Stage II. No significant differences in weight and height were found between PA groups at both Tanner Stage , At Tanner Stage I, the high PA group had very significantly higher bone density (p<0.01). The high PA group at Tanner stage II also had significantly higher density (p<0.05). There were significant difference between moderate PA group and low PA group in both Tanner Stage(p<0.05)

Discussion/Conclusions

Bone adapts its BMD and geometry properties in response to PA both at prepubertal and peripubertal stage. The impact of daily PA on bone density is more pronounced at prepubertal than peripubertal stage, The differences in bone density between different PA groups might become smaller when the girls transferred from prepubertal to peripubertal stage. This needs to be confirmed by further longitudinal studies.

References

[1]. Bailey, D.A. Faulkner, R.A.& McKay, H.A. Growth, PA, and bone mineral acquisition. Exercise Sport Sci Re 24, 2733-66 (1996).
[2]. DelVaux, K. et al. Bone mass and lifetime PA in Flemish males: a 27-year follow-up study. Med Sci Sports Exercise 33, 1868-75 (2001).
[3]. Kannus, P. et al. Effect of starting age of PA on bone mass in the dominant arm of tennis and squash players. Ann Intern Med 123, 27-31 (1995).