A biomechanical analysis of the plantar surface of soccer shoes

The incidence of severe injuries for soccer players may lead to long-term inactivity or, at worst, retirement from the game. Many of these injuries, particularly those involving the lower leg, can be attributed to adverse physical conditions at the interface between the soccer shoe and the playing support surface. This study investigated the biomechanical characteristics at this interface for a range of proprietary soccer shoes. An experimental system was designed and developed which, via a weighted pendulum arm making contact with a vertical column, provided controlled rotation of the forefoot of the soccer shoe on samples of playing surfaces. The overall rotation was found to depend on several physical and material factors. For example, the size 7 soccer shoes produced a statistically significant increase in axial rotation for the same impact energy compared to the larger sized shoes under test. In addition, flat soled shoes, designed for synthetic playing surfaces, produced consistently smaller rotations than shoes with either moulded or screw-in studs, although this finding depended on the moisture content of the playing surface. The pressure distribution within several soccer shoes was also measured using the F-Scan Gait Analysis System, for a subject walking across a grass surface. Results indicated differences in pressure distribution over the first metatarsal area of the foot, in existing shoe designs.