Differences in Friction Performance between New and Worn Shoes.

TECHNICAL ABSTRACTBackground As slip-resistant shoes are naturally worn, the coefficient of friction (COF) decreases. Proper and timely shoe replacement is an important factor for preventing injuries related to slips. Knowledge of the change in COF for naturally worn shoes in the workplace, relative to the COF of their new counterparts, is needed for a better understanding in this area. Methods: Slip-resistant shoes worn in the workplace and their new counterparts were mechanically tested to assess their COF. Eighteen pairs of shoes (new and worn) were tested on a whole-shoe slip testing device that simulates under-shoe slipping conditions. The COF was calculated for each pair of shoes at a shoe-floor angle of 17 ± 1° relative to the ground surface, a speed of 0.5 m/s, and a mean normal force of 250 ± 10 N. Results: A mean decrease in COF of 0.055 (25%) was observed when comparing the naturally worn shoes with the new shoes. New shoes with an initial higher COF showed a larger loss in COF due to wear. Conclusions: Naturally worn, slip-resistant shoes have substantively reduced COF compared to their new counterparts. These findings demonstrate the potential for programs that monitor and replace slip-resistant shoes as a means to prevent slips.