Grant: Alliance Grants

Falls are the leading causes of unintentional injuries in Canada, increase exponentially with age and are more prevalent in older women. Nearly one third of them are falls on the same level from slipping, tripping and stumbling or falls due to ice and snow. Canadian footwear manufacturers thus constantly strive to develop new slip resistant footwear, but existing Canadian and international standards for evaluating footwear slip resistance have been recently questioned. Many factors can influence sole slip resistance, including intrinsic parameters such as compound material properties and sole tread shape, width or depth, but the basic mechanical principles most likely driving sole slip resistance are still misunderstood. Extrinsic parameters may also affect footwear slipping, such as the presence of fluids or particles, ground characteristics, or gait patterns of the wearer, but there are few studies with sufficiently large slips that balance recovery and avoiding a fall is not always possible. The overall goal of this research project is to get a better understanding of what leads to footwear slipping, so as to contribute to the reduction of slip injuries, in three ways: a) by investigating how intrinsic sole design parameters affect the available coefficient of friction at the footwear-ground interface, both in the first milliseconds of a slip and during slipping; b) by measuring the effect of extrinsic slip parameters on the required coefficient of friction during human gait experimental studies, with sufficiently large slips that avoiding a fall is not always possible; and c) by relying on new insights acquired from a and b, we will suggest new ways to evaluate footwear slip resistance for certification purposes and new sole designs for Canadian women and men of all ages. Specifically, by the end of this research project, we want to improve the coefficient of friction of footwear by 10-20% on wet ceramic and dry ice. Moreover, we hope to eliminate slip resistance performance differences between women and men footwear models.