Changes of bone mineral density after 30-week exercise program in premenopausal years

Introduction

Functional disorders in cardiac-pulmonary system and changes in muscular-skeletal system take place in people’s senescence. Muscle masses and muscular strengths reduce, ligaments and tendons weaken, and flexibility of joints decreases. The progressive increase in the loss of calcium content of the bones results in the reduction of bone density and the bones become more vulnerable to mechanical stresses. Osteoporosis is one of the symptoms of senility and most adults ordinarily experience increase in medullary cavity and reduction in bone mass. Researches have investigated the relevance between physical training and bone mineral density. However, most of them were focussed in postmenopausal women. This study is focused on women before menopause. Since a significant part of reduction of bone mineral density gradually takes place before menopause, high bone mineral density increase in premenopausal years would be critical to cope with the reduction of bone mineral density in postmenopausal years. The purpose of this study was to investigate the effect of exercise training on the bone mineral density of premenopausal women.

Methods

25 women, aged from 26 to 42 years, were used as subjects for the study. All of them were healthy with normal body weight and free of any disorder which might affect the bone metabolism. They neither had been pregnant nor had lactated within the previous two years. The subjects were randomly divided into two groups: a controlled group(10) and a weight training group(11) The subjects in the weight training group participated in 30 weeks of weight training program. Muscular strengths of the subjects were measured with 1 RM. The bone mineral density of lumbar was measured three times: before the investigation, 15 weeks after the investigation started, at the end of the investigation. All the subjects took 500mg calcium supplement everyday. The purpose of this study was to investigate the effect of exercise training on the

Results

During the study, a 048.7% increase in muscular strength was observed in the weight training group. However, this increase in muscular strength was not accompanied with statistically significant changes in the BMD(Bone Mineral Density). The mean of lumber BMD in the weight training group slightly increased by 0.337%, which was a statistically insignificant change, while the mean of lumbar BMD in the control group decreased by 0.338%, which was also a statistically insignificant one. Statistical analysis revealed that there was no significant difference in the percentage change in the lumbar BMD between the two groups.

Discussion / Conclusions

In spite of this statistical insignificance of the results, the fact that while the BMD of subjects in the controlled group reduced, the BMD in the weight-training group slightly increased may bring substantial differences in the long-term. Therefore, there is a potential that the chronic weight training may have on preventing effect on loosing BMD, and may also even have an increasing effect on BMD.

References

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[3]. Cavanaugh, D, J. & Cann, C. E.(1988). Brisk walking does not stop bone loss in postmenopausal women. Bone.9,201-204.