[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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To examine how heel contact provides trunk stabilization, we propose a simple model of muscle fiber arrangement for the femoral region of the human leg. The model comprises three parts: (i) an antagonistic pair of mono-articular muscles at the hip joint, (ii) an antagonistic pair of mono-articular muscles at the knee joint, and (iii) a two-joint link model incorporating an antagonistic pair of biarticular muscles that is simultaneously involved in hip and knee joint movement. On the basis of this simplified model, leg movement was analyzed using electromyography (EMG) and robotic kinematic. EMG analysis shows that during heel contact, electrical discharges occur simultaneously in the pair of antagonistic bi-articular muscles in the femoral-region; the rectus femoris and hamstrings. The robotic kinematic analysis shows that this simultaneous electrical discharge is necessary for controlling not only output forces at the heel as the point of contact, but also the stiffness ellipse. These results clearly indicate that the heel contact point is a major contributor to postural stability at time of contact.

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Ballet dancers have to perform their movements, especially with arms to express emotion or a role on the stage. Although the movement with their arms to express artistic or emotional impression might be difficult to master, no study has examined the 3-dimensional biomechanical characteristics of upper limb movements of ballet dancers. So, the purpose of this study was to clarify the characteristics of the skilled upper limb joints movements when ballet dancers are performing the flaps of swan wings movement in Swan Lake. Five expert female dancers and 9 inexperienced age-matched females participated in the study. Nineteen reflective markers were attached to the trunk and upper limbs, and then the upper limb motion in the“ Swan Lake” was captured with 12 optical cameras. Peak values of the upper limb joints angles (shoulder, elbow, and wrist joint) and the time lag of each peak value of the upper limb joints angles were compared between groups using unpaired t test. Significance level was set at p < 0.05. As a result, the upper limb joints angles of each group showed different especially in shoulder internal rotation, elbow flexion/extension, and elbow pronation. Moreover, the time lag of upper limb joints angles of each group showed different by upward and downward arm movement. Therefore, the shoulder internal rotation, elbow flexion/extension, and elbow pronation would be one of the fundamental skills to perform the swan wings expression, and the necessary skills of upper limb joints movements are different by upward and downward arm movement when ballet dancers express the flattering swan.

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We estimated muscle force and activity on gait with various plantar flexion resistive moment Ankle Foot Orthosis (AFO) by musculoskeletal model and AFO model, and performed muscle activity and ankle muscles force. Two healthy subjects were measured in five conditions: without an AFO and with an AFO with four different amount of planter flexion resistive moment. In estimated muscles activity, Tibialis Anterior, Gastrocnemius Medial head, Biceps Femoris, Gluteus maximus were medium to high correlated with experimental muscles activity, and in AFO condition, they were showed similarity value. In estimated muscles force, All AFO condition’s Tibialis Anterior tended to decrease compared with no AFO condition. Gastrocnemius Medial head tended to increase compared with no AFO condition.

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Recently, there has been extensive development in the field of bipedal robots. Some robots with the muscular arrangement of human leg by the mono-articular muscles and bi-articular muscles demonstrated stable walking motion. However, there were few examples that relations between the muscular arrangement and its motion control were examined in detail and applied the result to motion control of robot directly. This study focused on one of the effects of the bi-articular muscles on standing static stability by developing a bipedal robot with the muscular arrangement. The standing static stability was analyzed and experimented by using the relationship between stiffness characteristics and inverse pendulum model of the robot. The standing static stability was improved by one of the unique functions of the bi-articular muscles without using complex computer control.

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