Slipperiness of the shoe-floor interface: comparison of objective and subjective assessments

doi:10.1016/0003-6870(93)90460-Q

Applied Ergonomics

Volume 24, Issue 4, August 1993, Pages 258-262

https://doi.org/10.1016/0003-6870(93)90460-Q Get rights and content

Abstract

Tribollogically and biomechanically valid slip-resistance measurement methods are needed urgently to facilitate new developments for improving the safety of footwear and floor coverings. Objective coefficient-of-friction measurements and subjective walking experiments were compared to scrutinize and validate anti-slip assessments of the shoe-floor interface. Four shoe types were tested on a smooth stainless steel floor contaminated with viscous glycerol. The friction utilization ratio during one step, the sliding distance, and the subjective rating of slipperiness were evaluated by seven test subjects in 420 walking trials. All subjects assessed the footwear in the same rank of slipperiness. The friction utilization ratios during the walking trial were a poor indicator for anti-slip assessments. The apparatus-based kinetic friction values μ_k1, however, were more valid and, in particular, more reproducible. The safe level of μ_k1 was approximately 0.22, which is in accordance with previous slip-resistance clasification of shoes and floors. Futher trials in other shoe-contaminant-floor conditions and walking tasks are needed to verify the findings in this study.

References (10)

G.W. Harris et al.
Slip resistance of floors: users' opinions, Tortus instrument readings and roughness measurement
J Occup Accid
(1988)
K. Jung et al.
An international comparison of test methods for determining the slip resistance of shoes
J Occup Accid
(1990)
R.O. Andres et al.
Ergonomic analysis of slip-resistance measurement devices
Ergonomics
(1985)
R. Grönqvist
Mechanisms of friction and assessment of slip resistance of new and used footwear soles on contaminated floors
R. Grönqvist et al.
An apparatus and a method for determining the slip resistance of shoes and floors by simulation of human foot motions
Ergonomics
(1989)

There are more references available in the full text version of this article.

Cited by (52)

Machine learning prediction of footwear slip resistance on glycerol-contaminated surfaces: A pilot study
2024, Applied Ergonomics
Slippery surfaces due to oil spills pose a significant risk in various environments, including industrial workplaces, kitchens, garages, and outdoor areas. These situations can lead to accidents and falls, resulting in injuries that range from minor bruises to severe fractures or head trauma. To mitigate such risks, the use of slip resistant footwear plays a crucial role. In this study, we aimed to develop an Artificial Intelligence model capable of classifying footwear as having either high or low slip resistance based on the geometric characteristics and material parameters of their outsoles. Our model was trained on a unique dataset comprising images of 37 indoor work footwear outsoles made of rubber. To evaluate the slip resistant property of the footwear, all samples were tested using a cart-type friction measurement device, and the static and dynamic Coefficient of Frictions (COFs) of each outsole was determined on a glycerol-contaminated surface. Machine learning techniques were implemented, and a classification model was developed to determine high and low slip resistant footwear. Among the various models evaluated, the Support Vector Classifier (SVC) obtained the best results. This model achieved an accuracy of 0.68 ± 0.15 and an F1-score of 0.68 ± 0.20. Our results indicate that the proposed model effectively yet modestly identified outsoles with high and low slip resistance. This model is the first step in developing a model that footwear manufacturers can utilize to enhance product quality and reduce slip and fall incidents.
An observational ergonomic tool for assessing the worn condition of slip-resistant shoes
2020, Applied Ergonomics
Worn shoes are known to contribute to slip-and-fall risk, a common cause of workplace injuries. However, guidelines for replacing shoes are not well developed. Recent experiments and lubrication theory suggest that the size of the worn region is an important contributor to the shoe tread's ability to drain fluid and therefore the under-shoe friction. This study evaluated a simple test for comparing the size of the worn region relative to a common object (AAA and AA battery) as a means of determining shoe replacement. This study consisted of three components involving slip-resistant shoes: Experiment #1: a longitudinal, mechanical, accelerated wear experiment; Experiment #2: a longitudinal experiment where the same shoes were tested after each month of worker use; and Experiment #3: a cross-sectional experiment that exposed participants to a slippery condition, while donning their own worn shoes. The COF (Experiments #1 and #2); under-shoe fluid pressure (all experiments); and slip severity (Experiment #3) were compared across outcomes (fail/pass) of the battery tests. Larger fluid pressures, lower coefficient of friction, and more severe slips were observed for shoes that failed the battery tests compared with those passing the tests. This method offers promise for assessing loss in friction and an increase in slip risk for slip-resistant shoes.
Relationship among several measurements of slipperiness obtained in a laboratory environment
2018, Applied Ergonomics
Multiple sensing mechanisms could be used in forming responses to avoid slips, but previous studies, correlating only two parameters, revealed a limited picture of this complex system. In this study, the participants walked as fast as possible without a slip under 15 conditions of different degrees of slipperiness. The relationships among various response parameters, including perceived slipperiness rating, utilized coefficient of friction (UCOF), slipmeter measurement and kinematic parameters, were evaluated. The results showed that the UCOF, perceived rating and heel angle had higher adjusted R² values as dependent variables in the multiple linear regressions with the remaining variables in the final pool as independent variables. Although each variable in the final data pool could reflect some measurement of slipperiness, these three variables are more inclusive than others in representing the other variables and were bigger predictors of other variables, so they could be better candidates for measurements of slipperiness.
Perceiving slipperiness and grip: A meaningful relationship of the shoe-ground interface
2017, Gait and Posture
Citation Excerpt :
In order to prevent slips and falls, previous studies have investigated the relationship between available and utilized coefficient of friction (CoFA and CoFU, respectively) in different situations and environments [8–12]. CoFA refers to the maximum friction available for a given shoe-floor interface and it is measured mechanically with either laboratory devices [9,13] or in-field portable devices [8,10,11]. CoFU refers to the biomechanically measured friction of the shoe-floor interface during gait [8–11,14,15].
The present study investigated the relationship between objective measurements of the available (CoF_A), the utilized (CoF_U) coefficient of friction and subjective perception of grip or slipperiness. It was hypothesized that significant correlations exist between the perception of grip or slip and the CoF during sports movement and that a minimum CoF was needed to ensure an optimal grip/slipperiness perception. Eighteen healthy active females performed forward and backward cutting tasks onto a forceplate. Six shoes and two floors were used to induce different grip conditions. Subjective ratings and CoF_U were assessed for each shoe-floor combination, and mechanical CoF_A was also measured in a specific test bed. Significant relationships (p < 0.001) were found between grip, slipperiness ratings or CoF_A with the CoF_U (r = 0.98, r = −0.97, r = 0.88, respectively). Individual sensory thresholds of the minimum required CoF_U were also determined using probit models between the CoF_U and the grip acceptability. The mean threshold defined in the present study was 0.70 ± 0.11. This meant that below this threshold, the grip perception was not acceptable, whereas above this threshold, the grip was felt good enough to perform the task. In conclusion, strong relationships between subjective perceptions and objective measurements of friction were found in sports-like movements. Moreover, a minimum friction requirement was defined for indoor dry shoe-floor conditions. The present study gives new insights of the shoe-floor interaction and outlines friction requirements for the manufacturers of sports floor or footwear.
In shoe pressure measurements during different motor tasks while wearing safety shoes: The effect of custom made insoles vs. prefabricated and off-the-shelf
2016, Gait and Posture
Citation Excerpt :
Despite the increasingly strict regulations on safety shoes quality, which promote to minimize injuries and loss of working days, and the increasing rate of foot and musculoskeletal ailments reported in factory workplace, very little has thus far been investigated to improve workers’ comfort and to increase our understanding on the biomechanics of the foot inside safety shoes. Safety shoes have been tested for the properties of their materials and components [25], slip resistance [26], and comfort [19,22]. The effects of custom insoles on different musculoskeletal diseases have also been extensively reported [13,14,16].
Health and safety regulations in many countries require workers at risk to wear safety shoes in a factory environment. These shoes are often heavy, rigid, and uncomfortable. Wearing safety shoes daily leads to foot problems, discomfort and fatigue, resulting also in the loss of numerous working days. Currently, knowledge of the biomechanical effects of insoles in safety shoes, during working activities, is very limited.
Seventeen workers from a metalworking factory were selected and clinically examined for any foot conditions. Workers feet were 3D scanned, with regards to their plantar view, and the images used to design 34 custom-insoles, based on foot and safety shoe models.
Three insoles were blind-tested by each worker: custom (CUS); prefabricated with the safety-shoe (PSS), and off-the-shelf (OTS). Foot-to-insole pressure distribution was measured in seven motor tasks replicating typical working activities: single and double-leg standing; weight lifting; stair ascending and descending; normal and fast walking.
Wearing CUS within safety shoes resulted in a greater uniform pressure distribution across plantar regions for most of the working activities. Peak pressure at the forefoot during normal walking was the lowest in the custom insole (CUS 275.9 ± 55.3 kPa; OTS 332.7 ± 75.5 kPa; PSS 304.5 ± 54.2 kPa). Normal and fast walking were found to be the most demanding activities in terms of peak pressure.
Wearing safety shoes results in high pedobarographic parameters in several foot regions. The use of custom insoles designed on the foot morphology helps decrease peak pressure and pressure-time integral compared to prefabricated featureless insoles.
Roughness and slipperiness of floor surface: Tactile sensation and perception
2011, Safety Science
Citation Excerpt :
They reported that the correlation between subjective rating and the COF was strong (r ⩾ 0.75). Grönqvist et al. (1993) compared subjective ratings with the COF of liquid-contaminated floor surfaces. They reported a significant correlation (r = 0.97) between the two measures.
The slipperiness of floor is one of the risk factors affecting the occurrence of slipping and falling. The purpose of the study was to compare the roughness and slipperiness of five floor surfaces based on tactual sensations from different body segments for human subjects. The perceived roughness and perceived floor slipperiness of five floors based on tactual sensation from 20 male and 20 female subjects were collected and compared. The female subjects tended to give higher subjective ratings on both perceived roughness and slipperiness than their male counterpart. Both index fingertip and palm were more sensitive than foot in the sensation of floor roughness. The differences among fingertip, palm, and foot in the perceived floor slipperiness were not statistically different. The regression analysis results indicated that floor roughness parameter R_a is a better predictor in predicting both the perceived floor roughness and perceived floor slipperiness than the COF of the floor.

View all citing articles on Scopus

View full text

Slipperiness of the shoe-floor interface: comparison of objective and subjective assessments

Abstract

J Occup Accid

J Occup Accid

Ergonomic analysis of slip-resistance measurement devices

Ergonomics

Mechanisms of friction and assessment of slip resistance of new and used footwear soles on contaminated floors

An apparatus and a method for determining the slip resistance of shoes and floors by simulation of human foot motions

Ergonomics