Biomechanical variables associated with cleated footwear slipping

Thirty-four male participants performed a rapid change of direction cutting task at maximal effort wearing the same footwear conditions (Nike Vapour Edge Speed 360) on an infilled artificial turf surface (FieldTurf Inc.). The task consisted of the participant sprinting towards the force platform, performing a 180 turn and then sprinting away from the force platform as quickly as possible. The artificial turf surface was constructed with a low carpet fibre faceweight (reduced number of fibres) compared to a conventional surface, allowing for increased infill movement, and providing a surface that reduced traction and fostered footwear slippage. A motion capture system (240Hz) and force platform (2400Hz) were used to quantify the movement/orientation of the shoe and the forces generated during the change of direction movement. All trials were classified into one of three categories based on the horizontal displacement of the forefoot during the stance phase of the change in direction: (i) stick, which represented the lowest movement (25% of trials), (ii) standard, which represented the average movement (50% of trials), and (iii) slip, which represented the highest movement (25% of trials). Biomechanical data was then statistically compared to the Standard condition using a paired t-test (alpha 1⁄4 0.05).