[The effect of the motion of forefoot joint at the force exerted upon the floor during walking exercise]

In walking exercise the human body is exposed to external forces. Some of them are produced by constraints such as surface, shoes or opponent. In kick action of walking, the ground reaction force (GRF) is the most important external force. The magnitude of the GRF, its direction, and point of application have an influence on the load on the human body. The purpose of this study is to clarify the role of forefoot joint (artt. metatarsophalangeae) at the force exerted upon the floor during kick action of walking. The device used in this study to analyze the GRF and its three components consists of Kistler's force platform. Output from force transducer was collected online with a TEAC data recorder and MEM-4101 minicomputer. The impact force measurements were taken from the anterior-posterior force time curves at the take-off for 1 subject walking 10 trials at 2 m/sec with 2 different pairs of shoes (Shoes 1: thin sole of 4mm, and Shoes 2: thick sole of 40mm) and without shoes. High speed (200f/sec) cinematography was also used to analyze the angular displacement of forefoot joint at the take-off of walking exercise. The force acting at the forefoot joint may produce the anterior-posterior force of the GRF which is defined as the propelling power acting on the human body during walking exercise. The result showed that the impact force peak occurred 40-60 msec before take-off and the propelling part of kick action accounted for only about 6% of the external force.(ABSTRACT TRUNCATED AT 250 WORDS)