- Distribution of Calcaneal Bone Density According to the Mechanical Strain of Exercise and Calcium Intake in Premenarcheal Girls.
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Eun Kyung Shin, Ki Suk Kim, Hee Young Kim, In Sook Lee, Hyo Jee Joung, Sung Il Cho
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J Prev Med Public Health. 2005;38(3):291-297.
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 Abstract
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- OBJECTIVE
The effects of exercise on bone density have been found to be inconsistent in previous studies. We conducted a cross-sectional study in premenarcheal girls to test two hypotheses to explain these inconsistencies. Firstly, "the intensity of mechanical strain, in terms of the ground reaction force (GRF), has more important effects on the bone mass at a weight-bearing site", and secondly, "calcium intake modifies the bone response to exercise". METHODS: The areal bone mineral density was measured at the Os calcis, using peripheral dual energy X-ray absorptiometry, in 91 premenarcheal girls aged between 9 and 12 years. The intensity of mechanical strain of exercise was assessed by a self-report questionnaire and scored by the GRF as multiples of body weight, irrespective of the frequency and duration of exercise. The energy and calcium intake were calculated from the 24-hour dietary recall. An analysis of covariance (ANCOVA) was used to determine the interaction and main effects of exercise and calcium on the bone density, after adjusting for age, weight, height and energy intake. RESULTS: The difference in the bone density between moderate and low impact exercise was more pronounced in the high than low calcium intake group. The bone density for moderate impact exercise and high calcium intake was significantly higher than that for low impact exercise (p=0.046) and low calcium intake, after adjusting for age, weight, height and energy intake. CONCLUSIONS: Our study suggests that the bone density at a weight-bearing site is positively related to the intensity of mechanical loading exercise, and the calcium intake may modify the bone response to exercise at the loaded site in premenarcheal girls.
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- The Association between Bone Density at Os Calcis and Body Composition in Healthy Children Aged 9-12 Years.
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Eun Kyung Shin, Ki Suk Kim, Hee Young Kim, In Sook Lee, Hyo Jee Joung, Sung Il Cho
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J Prev Med Public Health. 2004;37(1):72-79.
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- OBJECTIVE
This cross-sectional study aimed to quantify the relationship between the bone mineral density at the os calcis and the body mass composition in healthy children. METHODS: The areal bone mineral density was measured at the os calcis with peripheral dual energy X-ray absorptiometry. The fat free mass, fat mass and percentage fat mass were measured using bioelectric impedance, in 237 Korean children, aged 9 to 12 years. The sexual maturity was determined by self assessment, using standardized series of the 5 Tanner stage drawings, accompanied by explanatory text. RESULTS: From multiple linear regression models, adjusted for age, sexual maturity and height, the fat free mass was found to be the best predictor of the calcaneal bone mineral density in both sexes. About 15 and 20% variabilities were found in the calcaneal bone mineral densities of the boys and girls, respectively, which can be explained by the fat free mass. After weight adjustment, the percentage fat mass was negatively associated with the calcaneal bone mineral density in both sexes. CONCLUSIONS: The findings of this study suggest that the fat free mass, among the body compositions, is the major determinant of bone mineral density at the os calcis in Korean children aged 9 to 12 years. Obesity, defined as the percentage fat mass, is assumed to have a negative effect on the calcaneal bone density in children of the same weight.
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