On the ‘trench effect’ theory: A biomechanical analysis of the relationship between traction and shoe orientation on third-generation artificial turf

Abstract

Background: Based on mechanical device testing on third-generation artificial turf (3G turf) it has been theorised that when cleated shoes are rotated at an angle to the direction of sliding in the transverse plane, the number of separate cleats forced to carve unique paths through the infill increases, thus increasing translational traction (termed ‘trench effect’). The aim of the study was to investigate whether the magnitude of this angle (shoe trench angle) affected traction across cleat configurations and 3G turf systems during a standardised in vivo change of direction movement.Methods: Twenty-two male soccer players (mean ± SD: age, 23.1 ± 2.8 years; height, 1.81 ± 0.06 m; body mass, 77.5 ± 6.0 kg) performed five short sprints with a 90° cut over a turf covered force plate for each combination of three turf systems and three cleat configurations. The traction coefficient – shoe trench angle relationship across cleat configurations and turf systems was determined with an analysis of covariance (ANCOVA) and shoe displacement was assessed with a linear mixed model.Results: There was a significant positive slope of the traction coefficient – shoe trench angle relationship, with a predicted increase in traction coefficient of 0.0017 for every degree of medial shoe rotation. The relationship did not differ between cleat configurations or turf systems. Across all shoe-surface combinations, mean ± SD shoe displacement was 1.33 ± 0.60 cm.Conclusion: During a standardised in vivo change of direction movement, an increase in shoe trench angle was accompanied by an increase in traction coefficient. The order of occurrence of these variables in such a movement makes it reasonable to assume that the increase in shoe trench angle causes the increase in traction coefficient. However, the magnitude of shoe displacement makes it difficult to support the ‘trench effect’ theory for controlled human movement.