Bone Growth and its Effective Factors of the Girls in the Elementary School and the Women’s College Students

Abstract

To study bone growth and its effective factors, we measured broadband ultrasound attenuation (BUA) and speed of sound (SOS) on 81 healthy girls in the elementary school and 425 women’s college students, who were 18 years old, by means of ultrasound bone densitometry. The elementary school girls were measured twice ; first at grade 4 when their mean age was 9.5, and second at grade 5. General data on all the girls and female students were also obtained : 1) physical characteristics-height, weight, body mass index (BMI), lean body mass (LBM), body fat percentage (%Fat) ; 2) physical fitness-grip strength, back strength, vertical jump ; 3)other details-frequency of sports activity, menstruation cycle, milk and milk product intake. Finally, we statistically analyzed all data by using paired and Student' t-test, and simple regression analysis.

Results were as follows : 1) almost all factors except vertical jump showed a significantly increase for the year from grade 4 to 5; 2) significantly positive correlations existed between BUA and SOS in both groups of girls and students, between BUA and all factors in the female students, but BUA and all physical characteristics and fitness except vertical jump in the girls ; 3)there was no significant difference among correlation coefficients between BUA and SOS of either group ; 4) there were no significant correlations between SOS and all factors except BUA in the girls of irade 4, but significantly positive correlations appeared between SOS and all physical characteristics, except %fat. and left hand and mean grip strength in those of grade 5 ; 5) in the college students, there were significantly positive correlations between SOS and all physical characteristics except height. and vertical jump ; 6) the frequency of weekly sports club activity of the high SOS group was higher than that of the low ; 7) the frequency of milk and milk product intake of the elementary school girls was significantly higher than that of the college students.

In conclusion, significant correlations appeared between SOS, which shows the quantity of bone minerals, and physical characteristics and sports activity on beginning of the acute development. These are one of the characteristics of the growth period.