Experimental Analysis of the Distribution of Traction Coefficient in the Shoe-Ground Contact Area during Running

Relationship between shoe grip properties and distributions of traction coefficient, which is obtained from horizontal ground reaction force (GRF) divided by normal GRF, were experimentally investigated during running. The experiments were conducted with sensor shoes mounted miniature triaxial force sensors for the measurement of GRF distributions in contact area. In order to clarify influence of the grip property on GRF vectors distributions and traction coefficient distributions, two typed sensor shoes having different outer sole materials with high/low friction coefficients were developed. The results showed that traction coefficients for the low grip typed shoe decreased in the whole contact area at the end of stance phase during running. Furthermore, it was confirmed that contact area, directions of GRF vectors and traction coefficients locally changed depending on the grip property. As a result of relationship between distributions of propulsion force components at 19 local positions and stride length, production of propulsion force beneath toe area can efficiently acquire sufficient stride length to keep running speed.