Shoe-rung coefficient of friction as a predictor of slips in ladder climbing

Falls during ladder climbing can result in severe injuries. Foot slipping is a common initiating event of these falls. The available coefficient of friction (ACOF) and the required coefficient of friction (RCOF) are typically indicators of slip propensity. This study aimed to quantify the ability of shoe-rung frictional measures (ACOF, ACOF - RCOF) to predict slip outcomes during ladder climbing. ACOF values were obtained for eight ladder rungs in the presence of a liquid through mechanical slip-testing using three sets of testing parameters: generic, biofidelic, and subject-specific. RCOF values were obtained through baseline climbing trials. Then, a liquid contaminant was applied to create unexpected slippery conditions. Logistic regression analyses were used to model the impact of the frictional measures on slip outcomes in this contaminant trial. Lower ACOF values were associated with higher probabilities of slip outcomes. ACOF values obtained from biofidelic and subject-specific testing conditions (ACOF_B and ACOF_SS) were the best predictors, while ACOF - RCOF was not predictive of slip outcomes. Ladder rung designs with sufficient friction (especially non-slip rungs with rectangular cross-sections) can prevent slip events and the developed biofidelic testing parameters provide an opportunity to measure this risk.