Traction performance across the life of slip-resistant footwear: Preliminary results from a longitudinal study

Abstract

Introduction: Slips, trips, and falls are a major cause of injury in the workplace. Footwear is an important factor in preventing slips. Furthermore, traction performance (friction and under-shoe fluid drainage) are believed to change throughout the life of footwear. However, a paucity of data is available for how traction performance changes for naturally worn, slip-resistant footwear.

Method: The presented research is a preliminary analysis from an ongoing, larger study. Participants wore slip-resistant footwear while their distance walked was monitored. Friction and under-shoe fluid pressures were measured using a robotic slip tester under a diluted glycerol contaminant condition after each month of wear for the left and right shoes. The size of the worn region was also measured.

Results: Friction initially increased and then steadily decreased as the distance walked and the size of the worn region increased. Fluid pressures increased as the shoes were worn and were associated with increased walking distance and size of the worn region.

Discussion: Consistent with previous research, increases in the size of the worn region are associated with increased under-shoe fluid pressures and decreased traction. These trends are presumably due to reduced fluid drainage between the shoe-floor interface when the shoe becomes worn.

Conclusions: Traction performance changes with natural wear. The distance walked in the shoe and the size of the worn region may be valuable indicators for assessing loss of traction performance. Practical Applications: Current shoe replacement recommendations for slip-resistant shoes are based upon age and tread depth. This study suggests that tools measuring the size of the worn region and/or distance traveled in the shoes are appropriate alternatives for tracking traction performance loss due to shoe wear.

Keywords: Available coefficient of friction; Biomechanics; Footwear; Shoe wear; Slips, trips, & falls.

Copyright © 2020. Published by Elsevier Ltd.

Figures

Figure 1.

Shoe tread pattern at the heel for all shoes in this study.

Figure 2.

The robotic slip tester was used to slide the shoe across the contaminated surface along multiple parallel paths (adapted from Hemler, Charbonneau, et al., 2019).

Figure 3.

A) Molds of shoe heels were created at a 17° angle to capture the B) shoe tread geometry. C) The mold was used to measure the length and the width of the largest continuous area without tread at baseline and after each month of wear.

Figure 4.

A) ACOF plotted against the distance walked for each participant. B) ACOF across the distance walked in the shoes as a percentage of the baseline ACOF. ACOF and percent of baseline ACOF are averaged across left and right shoe sides.

Figure 5.

Fluid force values are plotted against the distance walked which was averaged across the left and right shoes per subject.

Figure 6.

A) ACOF plotted against the size of the worn region. Different markers are used for each participant (legend). B) Fluid force plotted against the size of the worn region for all participants. Left and right shoe averages are shown for each participant. The regression functions for each model are shown with the solid black line (SWR = size of worn region [mm2]). The regression equations and the R2 values are shown in the top left of each plot.