日本人高齢者の身体部分慣性特性

抄録

In the analysis of human movement, it is significant that appropriate parameters of the inertia property of body segments should be used because they will affect various computed kinetic variables. When analyzing the movement of elderly people, it is also desirable to use the inertia parameters of the body segments suitable for the elderly. Although there are appropriate sets of inertia parameters of the body segments for children (Yokoi et al., 1986) and young adults (Ae et al., 1992) of Japanese, no report exists on those for Japanese elderly. The purposes of this study were to determine the mass, the location of the center of mass (CM) and the principal moments of inertia about three axes of the body segments for Japanese elderly males and females by using an elliptical zone model (Jensen, 1978; Ae et al., 1992), and to develop a set of regression equations to estimate inertia parameters of the body segments using simple anthropometric measurements as predictors. Subjects were 90 Japanese elderly males aged 62 to 86 yr. (mean 75.1 yr.) and 89 Japanese elderly females aged 61 to 83 yr. (mean 73.0 yr.). Each subject, wearing swimming suit and cap, was photographed in a standing position in the measurement frame with a thin mirror mounted at an angle of 45° to the subject. Body segments were the head, whole torso, upper arms, forearms, hands, thighs, shanks, feet, upper torso and lower torso. They were modeled as a stacked system of elliptical zones 2cm in thickness. Segment density was assumed to be uniform and selected from 26 sets of segment densities after Dempster (1955) and Chandler et al. (1975). The mean errors in the estimation of total body mass were -0.07±0.54% (maximal error: -2.03%) for the males and -0.01±0.45% (maximal error: -1.27%) for the females. Equations for the estimation of the body segment inertia parameters were determined using a stepwise multiple regression with age, standing height, body weight and segment length as predictors. The results obtained could be summarized as follows: 1) There were significant differences in many body segment inertia parameters between the elderly males and females. The percent mass ratios of the forearm, hand, foot and upper torso for the elderly males were significantly larger than those for the elderly females, but the thigh, shank and lower torso ratios for the elderly females were significantly larger than those for the males. 2) There were significant differences in many body segment inertia parameters between the elderly and the young adults (Ae et al., 1992) and between the Japanese elderly and the Canadian elderly (Jensen et al., 1993; 1994). 3) The correlation coefficients between the body segment inertia parameters determined and estimated from the regression equations were all significant (0.328-0.979; p<0.01). The equations determined in this study should be valid for estimation of the body segment inertia properties for Japanese elderly.