著者
阿江 通良 湯 海鵬 横井 孝志
出版者
バイオメカニズム学会
雑誌
バイオメカニズム (ISSN:13487116)
巻号頁・発行日
vol.11, pp.23-33, 1992-05-20 (Released:2016-12-05)
被引用文献数
131 165

Inertia properties of the body segments such as segment mass, location of the center of mass, and moment of inertia can be measured and predicted in a number of ingenious approaches. They can be classified into a) direct measurements on cadavers, b) indirect measurements on living subjects, and c) mathematical modelling. However, there is little information upon which complete inertial estimates for Japanese people, especially male and female athletes, can be based. The purposes of this study were to determine the mass, center of mass location, and moments of inertia of the body segments for Japanese male and female athletes using a mathematical modelling approach, and to develop a set of regression equations to estimate inertia properties of body segments using simple anthropometric measurements as predictors. Subjects were 215 male and 80 female athletes belonging to various college sport clubs. Each subject, wearing swimming suit and cap, was stereo-photographed in a standing position. Ten body segments including the upper and lower torso were modelled to be a system of elliptical zones 2cm thick based on Jensen and Yokoi et al. Significant prediction equations based on body height, body weight, and segment lengths were then sought, and some prediction strategies were examined. The results obtained were summarized as follows: 1) Table 2 provides a summary of mass ratios, center of mass location ratios and radius of gyration ratios for males and females. There were many significant differences in body segment parameters between the two sexes. This suggests the need to develop different prediction equations for males and females. 2) Close relationships were noted between segment masses and segment lengths and body weight as predictors for all body segments. Table 5 provides coefficients of multiple regression equations to predict segment masses. 3) No close relationship was noted between independent variables and estimates of the center of mass location. This indicates that the variance in the center of mass location in proportion to the segment length was very small, and that location of centers of mass could be estimated by the mean ratio provided in Table 2. 4) Close relationships were noted between segment moments of inertia and segment lengths (except hand and foot), and body weight as predictors. Tables 6 and 7 provide coefficients of multiple regression equations to predict segment moments of inertia from segment lengths and body weight.
著者
湯 海鵬 阿江 通良 横井 孝志 渋川 侃二
出版者
バイオメカニズム学会
雑誌
バイオメカニズム (ISSN:13487116)
巻号頁・発行日
vol.10, pp.107-118, 1990-09-10 (Released:2016-12-05)

Twisting from a somersault is one of the most used techniques in sports with airborne components such as diving, gymnastics, and so on. The purposes of this study were to investigate the effect of arm swing on the production of aerial twist during somersault and to identify factors affecting the production of the twist. By using a model composed of three rigid bodies, the mechanism of the production of twist from a somersault was confirmed theoretically. Then, quantitative calculation was done based on the model. In the calculation a performer was assumed to swing one arm downward from the symmetrical position with both arms above the head. To validate the model, twisting somersaults of two male skilled gymnasts were filmed and analyzed with 3-dimensional cinematography (DLT method) to compare with the model. The performances were forward twist-somersaults of 1/2, 1 and 3/2 revolutions from a vaulting horse. The factors affecting the generation of twist are discussed based on the results of computer simulation and film data. The results are summarized as follows: 1) An asymmetrical arm swing could generate a twist about the longitudinal axis of the body from a somersault. This arm swing tilted the principal axes of the body away from their original positions. The axis of the angular momentum that was initially established did not change in the airborne phase, but the momentum resolved into two perpendicular components, one about the body's principal longitudinal axis and the another about the body's frontal axis (principal axis). Thus, the somersaulting motion around the frontal axis will continue even though the frontal axis is now tilted from its original position, and in addition the body will begin to twist about its longitudinal axis. 2) The direction of the twist depended upon the initial directions of the somersault and/or arm swing. 3) Large angular velocity of the somersault before the change in the posture and large swing angle of the arm were effective for the generation of twisting. The smaller the moment of inertia about body's longitudinal axis, the larger the twisting that was produced.
著者
阿江 通良 湯 海鵬 横井 孝志
出版者
バイオメカニズム学会
雑誌
バイオメカニズム
巻号頁・発行日
vol.11, pp.23-33, 1992
被引用文献数
67 165

Inertia properties of the body segments such as segment mass, location of the center of mass, and moment of inertia can be measured and predicted in a number of ingenious approaches. They can be classified into a) direct measurements on cadavers, b) indirect measurements on living subjects, and c) mathematical modelling. However, there is little information upon which complete inertial estimates for Japanese people, especially male and female athletes, can be based. The purposes of this study were to determine the mass, center of mass location, and moments of inertia of the body segments for Japanese male and female athletes using a mathematical modelling approach, and to develop a set of regression equations to estimate inertia properties of body segments using simple anthropometric measurements as predictors. Subjects were 215 male and 80 female athletes belonging to various college sport clubs. Each subject, wearing swimming suit and cap, was stereo-photographed in a standing position. Ten body segments including the upper and lower torso were modelled to be a system of elliptical zones 2cm thick based on Jensen and Yokoi et al. Significant prediction equations based on body height, body weight, and segment lengths were then sought, and some prediction strategies were examined. The results obtained were summarized as follows: 1) Table 2 provides a summary of mass ratios, center of mass location ratios and radius of gyration ratios for males and females. There were many significant differences in body segment parameters between the two sexes. This suggests the need to develop different prediction equations for males and females. 2) Close relationships were noted between segment masses and segment lengths and body weight as predictors for all body segments. Table 5 provides coefficients of multiple regression equations to predict segment masses. 3) No close relationship was noted between independent variables and estimates of the center of mass location. This indicates that the variance in the center of mass location in proportion to the segment length was very small, and that location of centers of mass could be estimated by the mean ratio provided in Table 2. 4) Close relationships were noted between segment moments of inertia and segment lengths (except hand and foot), and body weight as predictors. Tables 6 and 7 provide coefficients of multiple regression equations to predict segment moments of inertia from segment lengths and body weight.