Moment of inertia of whole body using an oscillating table in adolescent boys

This study measured the moment of inertia of the body using the oscillating table method, and saw how it is affected by age and body size. One hundred and seventeen subjects of junior and senior high school boys of ages 13-18 participated in this study. Moment of inertia was measured in two postures of supine (Imx) and recumbent (Imy) positions. Both Imx and Imy account for the range from 5.6 to 14.0 kg m2 and 4.2 to 13.5 kg m2, respectively, and correlate linearly to body height (Ht) and body weight (W). The values of Imy/Imx becomes 93.6 and 95.2% independent of age and body size. The difference between Imx and Imy might be affected by projection areas on the frontal from the sagittal area of the body. The multiple regression analysis of Ht2 and W with regard to Im was performed to obtain the following multiple regression equations: Imx = 3.44 Ht2 + 0.144 W - 8.04 (R = 0.973), Imy = 3.52 Ht2 + 0.125 W - 7.78 (R = 0.972). When Imx and Imy were estimated using these equations, the standard deviation of error which calculates the percent differences between the estimated and measured values amounted to +/- 5% in Imx and Imy. The results suggest that, with Japanese boys, there is a relationship between the postures and body size (height or weight), independent of age.