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. 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 wear volume and the size of the worn region was also measured. Prior to wearing shoes at work, participants completed dry walking trials during which ground reaction forces were recorded across different types of shoes. The peak normal force, shear force, and required coefficient of friction (RCOF) were calculated. 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. 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. Wear rate was positively associated with peak RCOF and with peak shear force, but was not significantly related to peak normal forces. 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. 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. The finding that shear forces and particularly the peak RCOF are related to wear suggests that a person’s gait characteristics can influence wear. Therefore, individual gait kinetics may be used to predict wear rate based on the fatigue failure shoe wear mechanism.

This data set describes data from a progressive wear experiment. Shoes were tested at baseline (Month of Wear = 0) and after each month of use. Between tests, participants wore the shoe at their work environment for a period of 1 month. Multiple months of data were collected for each participant.

Progressive Wear Experiment Column Numbers

1. Column A (“Subject”) represents the assigned subject ID [1, 2].

2. Column B (“Month of Wear”) represents the completed number of months the shoes were worn [1, 2].

3. Column C (“Total Distance [km]”) represents the distance walked that the shoes were worn [1, 2].

4. Column D (“Distance per month [km]”) represents the distance walked the shoes were worn in the previous month [1].

5. Column E (“Shoe Brand”) represents the brand of the shoe.

6. Column F (“Shoe Code 3 (A/B/C)”) represents the shoe code designation between A, B, and C [1, 2].

7. Column G (“Hardness”) represents the Shore A hardness of the shoe outsole [2].

8. Column H (“Side”) represents the left or right shoe of the pair [1].

9. Column I (“ACOF”) represents the shoe average available coefficient of friction from the five slip testing trials [1].

10. Column J (“%ACOF from Baseline”) represents the shoe available coefficient of friction relative to the new condition [1].

11. Column K (“Fluid Force [N]”) represents the load supported by the fluid during slip testing [1].

12. Column L (“Peak Fluid Pressure [kPa]”) represents the peak fluid pressure measured between the shoe and flooring during slip testing.

13. Column M (“Contact Area [sq in]”) represents the measured contact area between the shoe and flooring during slip testing.

14. Column N (“Untreaded Length [mm]”) represents the length of the continuous worn region along the long axis of the shoe [1].

15. Column O (“Untreaded Width [mm]”) represents the width of the continuous worn region along the short axis of the shoe [1].

16. Column P (“Untreaded Region Location”) represents the location on the shoe heel where the measurement was acquired.

17. Column Q (“Worn Region Size [mm^2]”) represents the product of the untreaded length and width in mm2 [1]. This variable is known as the size of the worn region in [1].

References:

1.         Hemler, S.L., Pliner, E.M., Redfern, M.S., Haight, J.M. and Beschorner, K.E., 2020, Traction performance across the life of slip-resistant footwear: preliminary results from a longitudinal study. Journal of Safety Research 74, 219-225.

2.         Hemler, S.L., Sider, J, Redfern, M.S., Beschorner, K.E., 2021, Gait Kinetics Impact Shoe Tread Wear Rate. Gait & posture 86, 157-161.

Throughout the document, "null" indicates missing data. For the "Untreaded Region Location", values of "n/a" indicate that no untreaded region had yet formed on the shoe.