The purpose of this study was to investigate the role of infill material and fibre structure on the rotational traction associated with American football shoes on infill-based artificial surfaces. A mobile testing apparatus with a compliant ankle was used to apply rotations and measure the torque produced at the football shoe–surface interface. The mechanical surrogate was used to compare three infill materials in combination with three fibre structures, creating a total of nine unique surfaces. Infill material, fibre structure, and shoe design were all found to significantly affect rotational traction. The cryogenically processed styrene–butadiene rubber (SBR) infill yielded significantly higher peak torques than the ambient ground SBR and extruded thermoplastic elastomer (TPE) infills. An artificial surface with a nylon root zone yielded significantly lower peak torques than similar fibre surfaces without a nylon root zone. The size of infill particles and the presence of a nylon root zone may influence the compactness of the infill layer. These features may act to alter the amount of cleat contact with the infill, thereby influencing rotational traction. The amount of cleat contact with the surface may also be determined by the shoe design.
Keywords: rotational traction; artificial surface; ankle; knee; injury