A mechanical study of the influence of ankle joint angle on translational traction of soccer boots

Abstract

The shoe–surface interaction for soccer players has both safety and performance implications. This interaction has been widely researched in terms of outsole configuration and surface type. However, these investigations, particularly those involving translational traction, often neglect the approach angle of the foot in terms of a real-world setting. This investigation considers the foot position prior to injuries such as anterior cruciate ligament tears, and observes how the translational traction alters with various angles for simulated plantarflexion, dorsiflexion, calcaneal inversion and calcaneal eversion. It was hypothesised that, as these angles increased, the translational traction would decrease as there would be less contact area between the boot and the surface compared to the neutral, flat footform. A custom-built testing apparatus recorded the translational traction of a soccer boot moving in four different directions at different loading angles on both a natural grass and artificial grass playing surface. A one-way ANOVA was performed, with a post-hoc Tukey Test to determine the significant differences between the translational traction between each angle. It was found that the geometry of the outsole configuration, more specifically, the apparent contact area between the shoe and surface played a significant role in the level of traction obtained. These results highlight the importance of stud geometry, particularly with respect to movements when the foot is angled as it would be in a potential injury scenario. Manufacturers should consider the profile of studs relative to the expected movements to not induce excessive traction, which could lead to potential foot fixation and injury.