The influence of footwear sole hardness on slip initiation in young adults

Introduction: Based on mechanical testing, harder soled shoes have been shown to provide less slip resistance than softer soled shoes. Whether or not wearing shoes with a hard sole leads to increased slip probability has not been examined. Methods: Forty healthy adults participated. Each was randomized into a hard (N=20) or a soft sole shoe group (N=20). Subjects were tested under both non-slippery (high-pressure laminate) and slippery floor conditions (dry Teflon). A fall arresting harness was used for all trials. Slip events during the slippery floor trials were documented using a motion analysis system. Slip probability was compared between conditions using a Chi-square test. Results: The proportion of slip events in the hard sole group (35%) was statistically greater than the proportion of slip events in the soft sole group (0%; X2 = 8.485, P = 0.008). Conclusions: The results of this study demonstrate that slip probability is influenced by sole hardness, which suggest that shoe sole hardness should be considered when designing footwear aimed at decreasing slip risk.