THE EFFECT OF AMBIENT-TEMPERATURE ON THE SHOE-SURFACE INTERFACE RELEASE COEFFICIENT

Previous studies of the shoe-surface interface correlated foot fixatio n with cleat length, configuration, and material composition as well a s turf type and surface conditions. Our study examined the effect of t emperature on the rotational torsion resistance of artificial turf foo tball shoes. Five football shoe models, a flat-soled basketball-style turf shoe, a natural grass soccer-style shoe, and three multistudded t urf shoes, were studied on dry AstroTurf at five temperatures (range, 52 degrees F to 110 degrees F). An assay device, a prosthetic foot mou nted on a loaded stainless steel shaft, was used to determine the forc e necessary to release a shoe from the turf's surface. We used a torqu e wrench to apply a rotational force so that each shoe was pivoted cou nterclockwise through an are of 60 degrees. Our results indicated that release coefficients differ within and among the shoe models at vario us turf temperatures. We also found that an increase in turf temperatu re, in combination with cleat characteristics, affects shoe-surface in terface friction and potentially places the athlete's knee and ankle a t risk of injury. Based on an established risk criterion, which correl ated shoe-surface interface combinations in the laboratory with docume nted clinical occurrences, only the flat-soled basketball-style turf s hoe could be designated ''safe'' or ''probably safe'' at all five temp eratures.