幼年チンパンジー四足ロコモーション発達の運動力学

Abstract

The quadrupedal locomotion of three infant chimpanzees was studies and compared with that of two semi-adults. The posture, footfall order, phase duration, speed and foot force in locomotion were measured by means of the force plate and a 16-mm cine camera or video tape recorder. The infant animals moved freely without any attachments on the body. In ontogenic walking of chimpanzees, no clear trend was observed to change from the usual terrestrial pattern to the primate pattern. The free locomotion of chimpanzees from infancy to the semi-adult stage varied considerably. The ontogeny of quadrupedal locomotion in chimpanzees, starting with the four-limb standing position, to two years of age was divided into the following stages: 1) From two to three months of age: Beginning with the four-limb standing position and progressing to gliding advancement on the hands and feet. The forelimbs carry a larger part of the body weight than the himdlimbs during static standing posture. "Fist" walking is seen. The hip, knee and toe joints were always flexed. 2) From four months of age: The two diagonal limbs were simultaneously in the air while walking. Footfall order started. Stance phases were long. The step length was short. The foot was not placed near the position where the hand on the same side was placed. The cycle duration was long. The hindlimbs' maximum downward peak showed a significantly larger magnitude than the forelimbs'. 3) From six months of age: Constant and steady walking. The relative speed was slower in this stage than in older ones, if comparison was made between walks of the same cadence. When the equal relative speeds were compared, the accelerating maximum value of the hindlimb was larger in this stage than in older ones. 4) From nine months of age: "Knuckle" walking started. The step length became long. The cycle duration was short. The foot was placed on the outer or inner side of the hand on the same side. Stance phases became short. 5) From one year of age: The hindlimbs carry a clearly larger part of the body weight than the hindlimbs during the static standing posture. The relative speed was fast. Walking as well as galloping was included in the repertoire of quadrupedal locomotion. The hip, knee and the toe joints were extended. 6) Around two years of age: The animals were very active. The "crutch" was included in quadrupedal locomotion.