Tasuku Kimura

Biomechanical analysis of primate bipedal walking by computer simulation

Abstract A computer simulation technique was applied to make clear the mechanical characteristics of primate bipedal walking. A primate body and the walking mechanism were modeled mathematically with a set of dynamic equations. Using a digital computer, the following were calculated from these equations by substituting measured displacements and morphological data of each segment of the primate: the acceleration, joint angle, center of gravity, foot force, joint moment, muscular force, transmitted force at the joint, electric activity of the muscle, generated power by the leg and energy expenditure in walking. The model was evaluated by comparing some of the calculated results with the experimental results such as foot force and electromyographic data, and improved in order to obtain the agreement between them. The level bipedal walking of man, chimpanzee and Japanese monkey and several types of synthesized walking were analyzed from the viewpoint of biomechanics. It is concluded that the bipedal walking of chimpanzee is nearer to that of man than to that of the Japanese monkey because of its propulsive mechanism, but it requires large muscular force for supporting the body weight.

Dynamics of primate bipedal walking as viewed from the force of foot

Bipedal walking of the six species of anthropoid primates including man were examined by means of the force plate technique. Though each species has a particular pattern of bipedal walking, we can classify two types of patterns in these primates as far as the foot force is concerned. The first type includes the man, chimpanzee, and spider monkey and the second type contains the Japanese monkey, hamadryas baboon, and gibbon. It was emphasized that the similarity of man to the chimpanzee and spider monkey in bipedal walking has some evolutionary significance.

Compressive strength of the rat femur as influenced by hypergravity

Abstract Ultimate compressive strength was studied at mid-length of the femur of female rats centrifuged from the age of 30 days at either 2.76 or 4.15 g for 810 days. The correlation between strength and age, cuberoot of body mass, femoral length, cross-sectional area/π, outer and inner radius at femoral mid-length and γ-ray absorption is significant and positive in the control animals ranging from 30 to 840 days. Except for the correlation between strength and photon absorption, the same correlations are negative or negligible in the 2.76 g group. Analysis of covariance reveals these correlation differences to be significant as regards femoral length and inner radius. The ultimate compressive strength of bone at the femoral mid-length is 10% greater in the animals centrifuged at 2.76 g, as compared to all control animals, if the mean values are adjusted with respect to body mass and outer radius, respectively.

Maximum likelihood factor analysis of the effects of chronic centrifugation on the structural development of the musculoskeletal system of the rat

SummaryAt the age of 30 days female Sprague-Dawley rats were placed on a 3.66 m radius centrifuge and subsequently exposed almost continuously for 810 days to either 2.76 or 4.15 G. An age-matched control group of rats was raised near the centrifuge facility at earth gravity. Three further control groups of rats were obtained from the animal colony and sacrificed at the age of 34, 72 and 102 days. A total of 16 variables were simultaneously factor analyzed by a maximum-likelihood extraction routine and the factor loadings presented after rotation to simple structure by a varimax rotation routine. The variables include G-load, age, body mass, femoral length and cross-sectional area, inner and outer radii, density and strength at the midlength of the femur, dry weight of gluteus medius, semimenbranosus and triceps surae muscles.Factor analyses on A) all controls, B) all controls and the 2.76 G group, and C) all controls and centrifuged animals, produced highly similar loading structures of three common factors which accounted for 74%, 68% and 68%, respectively, of the total variance. The 3 factors were interpreted as:1.An age and size factor which stimulates the growth in length and diameter and increases the density and strength of the femur. This factor is positively correlated with G-load but is also active in the control animals living at earth gravity.2.A growth inhibition factor which acts on body size, femoral length and on both the outer and inner radius at mid-length of the femur. This factor is intensified by centrifugation.3.A muscle growth inhibition factor which is probably correlated with age and G-load but is also active at earth gravity. A tentative biomechanical interpretation of these 3 factors has been ventured.

Fractography of human intact long bone by bending

SummaryHuman intact tibiae were tested using the static bending method to learn about the relationship between the fracture surface and the failure mode. The bending test was applied to test pieces and to whole bones. The fracture surface was observed by scanning electron microscopy. The bone fracture is closely related to the architecture of the bone substance, especially to the direction of the Haversian canals and the lamellae. The failure mode and the sequence of the break line of the bone can be found out by the observation on the fracture surface. Hardly any crushing effects caused by the compressive force is seen. The mechanical properties of the fractured bone can be estimated to some extend by considering the direction of the break line and the failure mode. The strength calculated by the simple beam formula for elastic materials can not be obtained directly because of the plastic deformation of the bone. The results of the tensile test may be applied to the fracture using the static bending moment.ZusammenfassungUm die aktuelle Analyse vom Mechanismus des Knochenbruchs deutlich und ausführlich zu erfassen, wurden der Biegungsversuch und die Raster-Elektronenmikroskopische (REM) Untersuchung durchgeführt. Eine enge Beziehung zwischen dem Knochenbruch und den strukturellen Eigenschaften des menschlichen Knochens (Tibia), beziehungsweise der Verlaufsrichtung der Haverschen Kanäle und Lamellen, wurde festgestellt. Die Befunde der Bruchfläche, die mit der Hilfe von REM beobachtet werden, geben sichere Information in Bezug auf den Zerstörungstypus und die Richtungen der Bruchlinien; daraus läßt sich die Rolle des dynamischen Verhaltens des Knochens beim Bruch vermuten. Wegen der komplizierten mechanischen Eigenschaften der Knochenstruktur ist es unmöglich, wie bei der Zerstörung von elastischem Material, das homogen ist, die Fraktur mit einer Formel zu erfassen. Es wird auch erwartet, daß die Theorie von der Zugfestigkeit bei der Analyse des Knochenbruchs durch statische Biegekräfte (d.h. Biegungsfraktur) anwendbar ist.