Perceiving slipperiness and grip: A meaningful relationship of the shoe-ground interface.

The present study investigated the relationship between objective measurements of the available (CoF), the utilized (CoF) coefficient of friction and subjective perception of grip or slipperiness. It was hypothesized that significant correlations exist between the perception of grip or slip and the CoF during sports movement and that a minimum CoF was needed to ensure an optimal grip/slipperiness perception. Eighteen healthy active females performed forward and backward cutting tasks onto a forceplate. Six shoes and two floors were used to induce different grip conditions. Subjective ratings and CoF were assessed for each shoe-floor combination, and mechanical CoF was also measured in a specific test bed. Significant relationships (p<0.001) were found between grip, slipperiness ratings or CoF with the CoF (r=0.98, r=-0.97, r=0.88, respectively). Individual sensory thresholds of the minimum required CoF were also determined using probit models between the CoF and the grip acceptability. The mean threshold defined in the present study was 0.70±0.11. This meant that below this threshold, the grip perception was not acceptable, whereas above this threshold, the grip was felt good enough to perform the task. In conclusion, strong relationships between subjective perceptions and objective measurements of friction were found in sports-like movements. Moreover, a minimum friction requirement was defined for indoor dry shoe-floor conditions. The present study gives new insights of the shoe-floor interaction and outlines friction requirements for the manufacturers of sports floor or footwear.