Body composition measurement by electrical bio-impedance method to establish the effect of daily physical training in adolescents.

As part of an ongoing study on the effect of daily physical training on adolescents, body composition (percentage fat) was measured using the electrical bio-impedance method in a sample of Japanese students aged 15 years (77 sedentary males, 137 active males, 66 sedentary females and 54 active females), who were selected on the basis of their answers in a questionnaire about physical activity in a cardiac study involving 227.361 high school students. Subjects were divided into 4 weight categories (underweight, normal weight, overweight and severe overweight) using an obesity index. ECG and ultrasound cardiography (UCG) were used for all subjects to measure their left ventricular mass (LVM), which was taken as an indicator of the effect of training. Among the 4 weight category groups, a significant difference in the percentage of fat between sedentary and active subjects was found in the normal weight category of males. Correlation between the percentage of fat and the obesity index was significant in both sedentary and active subjects of both the genders, but correlation coefficients were lower for active subjects than for sedentary ones. The percentage of fat tended to be very low in subjects with increased LVM. Additionally, a significant difference in the amount of fat was found between runners and soccer players in active males with normal weight. These results suggest that there were differing degrees of the effect of training on reducing body fat and that this effect is most notable in males with normal weight.(ABSTRACT TRUNCATED AT 250 WORDS)