Running has now become one of Japan’s national sports. Many people go running on a regular basis, for various different aims. While many take up running to improve their physical health, there are an increasing number of people who in fact do damage to themselves in the form of leg injuries sustained while running. One of the causes of such injuries is choosing the wrong type of running shoes. The primary function of shoes is protecting the feet during running, and they need to absorb the shock upon contact with the ground while at the same time stabilizing the feet. However, making shoe soles softer to allow them to absorb the shock generates the problem that the feet become shaky and unstable. In other words, shock cushioning and stability are mutually contradicting properties, and it is difficult to achieve a good balance between the two. While shoe soles are a familiar part of everyday lives, running shoes hold such difficult challenges.
Our laboratories have worked together for a number of years to research the motions involved in sports such as soccer, golf, table tennis, gymnastics, and baseball pitching. It is no longer possible to discuss sports that test the limits of human motion without using scientific analysis. The results of such research are being applied in a wide range of areas, from training to skills evaluation. The research of running shoes is part of a new kind of challenge to develop sports equipment, which was prompted by demand from companies developing shoe sole material for running shoes.
Until now the material of shoe soles has largely been researched in relation to the movement of the feet. However, this method does not allow us to analyze impact cushioning and the stability of the feet. As a minimum, we require information regarding the movement of the feet, and the plantar pressure (the pressure field between the sole of the foot and its supporting surface) during running. We therefore decided to measure the motion of the feet using a three-dimensional motion analysis device (left photo). A marker that reflects the infrared rays is attached to the part of the body that one wishes to measure, and the three-dimensional motion of said body part is measured by a motion camera with an infrared ray projector. In order to measure the motion of the feet, infrared-reflective markers were attached to four points on the shoes and four points on the lower leg. At the same time, we decided to use a sheet pressure sensor to simultaneously measure the plantar pressure during motion (right photo). We also decided to attach infrared-reflective markers to the shoe soles (center photo), and simultaneously measure the change in shape of the materials using motion capture. Such simultaneous measurement is the first of its kind in the world. We also adjusted the arrangement of the motion camera in order to increase the accuracy of the measurement (left photo).
In researching sports it is necessary to establish appropriate problems in response to the tasks given, devise experimental methods (measurement methods, test subjects, experimental procedures, analysis methods, etc.) to solve those issues, and scientifically analyze and apply the given data to derive answers to the problem. The results of such research must ultimately be fed back to the actual places of training. We welcome potential students keen to experience “the scientific study of sports” as part of the Interdisciplinary Program of Biomedical Engineering, Assistive Technology and Art and Sports Sciences.