The role of surface roughness in the measurement of slipperiness

Prospective validity assessment of a friction prediction model based on tread outsole features of slip-resistant shoes

Shoe outsole design strongly influences slip and fall risk. Certain tread features that can be readily measured have been shown to predict friction performance. This research aimed to replicate those findings and quantify their ability to predict slipping. Participants (n = 34) were exposed to a low friction oil-coated floor surface, while wearing slip-resistant shoes. The coefficient of friction (COF) of each shoe were predicted based on tread surface area, the presence of a bevel, and hardness. The COF was measured, and the slip outcome was determined. Predicted and measured COF were correlated, and measured COF was a sensitive predictor of slip outcome. The relationship of predicted COF on slip outcome was weaker than anticipated and was not statistically significant. This study partially confirmed the ability of previous regression equations to predict COF. However, the effect size was weaker than previously reported and predicted COF was not sensitive for predicting slips.

Nanotechnology development in surgical applications: recent trends and developments

This paper gives a detailed analysis of nanotechnology's rising involvement in numerous surgical fields. We investigate the use of nanotechnology in orthopedic surgery, neurosurgery, plastic surgery, surgical oncology, heart surgery, vascular surgery, ophthalmic surgery, thoracic surgery, and minimally invasive surgery. The paper details how nanotechnology helps with arthroplasty, chondrogenesis, tissue regeneration, wound healing, and more. It also discusses the employment of nanomaterials in implant surfaces, bone grafting, and breast implants, among other things. The article also explores various nanotechnology uses, including stem cell-incorporated nano scaffolds, nano-surgery, hemostasis, nerve healing, nanorobots, and diagnostic applications. The ethical and safety implications of using nanotechnology in surgery are also addressed. The future possibilities of nanotechnology are investigated, pointing to a possible route for improved patient outcomes. The essay finishes with a comment on nanotechnology's transformational influence in surgical applications and its promise for future breakthroughs.

Progress in the applications of atomic force microscope (AFM) for mineralogical research

Mineral surface properties and mineral-aqueous interfacial reactions are essential factors affecting the geochemical cycle, related environmental impacts, and bioavailability of chemical elements. Compared to macroscopic analytical instruments, an atomic force microscope (AFM) provides necessary and vital information for analyzing mineral structure, especially the mineral-aqueous interfaces, and has excellent application prospects in mineralogical research. This paper presents recent advances in the study of properties of minerals such as surface roughness, crystal structure and adhesion by atomic force microscopy, as well as the progress of application and main contributions in mineral-aqueous interfaces analysis, such as mineral dissolution, redox and adsorption processes. It describes the principles, range of applications, strengths and weaknesses of using AFM in combination with IR and Raman spectroscopy instruments to characterization of minerals. Finally, according to the limitations of the AFM structure and function, this research proposes some ideas and suggestions for developing and designing AFM techniques.

Friction performance of resilient flooring under contaminant conditions relevant to healthcare settings

Flooring is among the factors known to influence slip and fall risk. Slips are common in the healthcare industry, where resilient flooring is prevalent. This study assessed coefficient of friction (COF) across resilient flooring products specific to conditions relevant to healthcare. The COF for eleven resilient flooring surfaces were tested in their dry condition and under six contaminant conditions. Data was analyzed using ANOVA and principal component analysis. The COF was strongly influenced by the contaminant condition (p < 0.001) with hand sanitizer and canola oil having the lowest COF values. COF was also influenced by the flooring product (p < 0.001) although to a lesser extent than the contaminant condition. The contaminants differentially affected the friction performance across the flooring products (interaction effect p < 0.001). These effects were described by the first two principal components. This study reveals high slipping potential for certain contaminants on resilient flooring and that flooring influences friction performance in contaminant-specific ways.

The effect of footwear outsole material on slip resistance on dry and contaminated surfaces with geometrically controlled outsoles

Previous studies have compared slip resistance of commercially available footwear, however, often lacking the ability to isolate factors such as material and surface properties, or/and geometry. The aim of this study was to compare slip resistance of geometrically identical shoes with varying outsole materials. Three left Ecco Xpedition III shoes were constructed out of three different outsole materials: polyurethane (PU), thermoplastic polyurethane (TPU) and vulcanised rubber (RU). The shoes were tested for dynamic coefficient of friction (DCOF) on a steel and a tile surface, without contamination and with glycerine and canola oil as contaminants. The shoes were significantly (p < 0.001) different from each other across all surface/contaminant conditions/combinations, with the PU having a significantly 61-125% (p < 0.001) higher DCOF on contaminated surfaces compared to the RU outsole.Practitioner summary: Previous research has suggested the importance of studying individual parameters separately of footwear in relation to slip resistance. In this study, we managed to construct geometrically identical shoes and compare the slip resistance between three different outsole materials. We found that the polyurethane outsole was the least slippery choice of material for this specific footwear model on contaminated surfaces.

The sliding-contact factor (ηsc): a novel index for slip risk definition

The causes of slip are multiple and depend on the mechanical and aesthetic characteristics of the surfaces in contact, and on external elements related to the specific situation. The non-slip characteristics of a surface can be evaluated by measuring the dynamic friction coefficient (DCoF). Hazardous conditions generally appear and progress over time as a result of use, aging-related natural degradation, lack of or incorrect cleaning and maintenance. This study focuses on the characteristics of roughness profiles of the surfaces in contact and aims at the identification of those roughness parameters that can allow a more reliable evaluation of both the "slip risk index" and of its change over time due to alterations of surface texture. The sliding-contact factor,ηsc, is identified as a candidate for the evaluation of slip risk, and is represented by a dimensionless number that can be calculated using only the data of some roughness parameters, measured by a handheld instrument (Portable Surface Roughness Measuring Instrument), portable and easy to use. The sliding-contact factorηsc allows the evaluation of the "slip risk index" of dry and water-contaminated surfaces and can increase the accuracy of the assessment of the "slip risk index” if evaluated through the DCoF only.

Article Highlights

Foot rubbing evaluation of friction between shoe and flooring

A simple and inexpensive method to evaluate slip resistance that can be readily introduced into the workplace is required. In the present study, we investigated the relationship between a simple sensory evaluation of anti-slipperiness by foot rubbing in standing and sitting positions and the actual friction properties obtained with in situ measurements at slip onset and during sliding. We also verified the possibility of identifying a hazardous area with a high slip-induced fall risk by the sensory evaluation scores. At the foot rubbing tests, more than half of the 15 participants in experiments could adequately perceive the slip resistance using the proposed method without any education on its perception. Furthermore, hazard detection scores, where a friction coefficient of 0.2 was detected as hazardous area, were obtained from optimal cut-off points of receiver operatorating characteristic curves for the participants with friction perception capability. The scores were 28.7, 20.7, 24.7, and 52.3/100 for the slip onset while standing, sliding while standing, slip onset while sitting, and sliding while sitting, respectively. From the viewpoint of hazard detection accuracies, the standing position was a better way than the sitting although limited to participants with the capability of perceiving friction. Based on the analysis of how to apply forces, the participants who showed a small movement of the center of pressure while standing or an increase in the vertical load while sitting had the capability of perceiving friction.

Modifiable intrinsic factors related to occupational falls in older workers

AIM

Identification of modifiable intrinsic factors for occupational falls is required for initiating effective fall prevention strategies for older workers. This study aimed to identify modifiable intrinsic factors related to falls during occupational activities among older workers.

METHODS

This retrospective study involved 1164 older workers (aged ≥60 years, workdays ≥4/month) sampled from 18 public employment agencies for seniors in Saitama, Japan. Participants were assessed regarding the following 10 modifiable intrinsic factors: multimorbidity, polypharmacy, fall-risk-increasing medication use, self-rated vision and hearing, functional strength, bilateral stepping, standing balance, executive function and visuospatial ability. The number of falls during occupational activities in the past year was also recorded.

RESULTS

In total, 111 falls occurred in 73 of the 1164 participants during occupational activities in the past year. A negative binomial regression model showed that use of fall-risk-increasing medications (incidence rate ratio [IRR]: 2.23, 95% confidence interval [CI]: 1.08, 4.60, P = 0.031), reduced functional strength (IRR: 1.81, 95% CI: 1.02, 3.21, P = 0.042), poor standing balance (IRR: 1.83, 95% CI: 1.09, 3.09, P = 0.023) and poor visuospatial ability (IRR: 1.56, 95% CI: 1.03, 2.36, P = 0.034) were independently associated with occupational falls.

CONCLUSIONS

Our findings suggest that the assessment of medication use, functional strength, standing balance and visuospatial ability in regular health checks in the workplace may be useful for screening older workers at risk of occupational falls. Geriatr Gerontol Int 2022; 22: 338-343.

In contrast to slip-resistant shoes, fluid drainage capacity explains friction performance across shoes that are not slip-resistant

Slip and fall injuries can be prevented through footwear with good friction performance. The factors that contribute to friction in non-slip-resistant (NSR) shoes are not well understood. The purpose of this study was to determine whether predictive models for slip-resistant (SR) shoes also apply to NSR shoes. This study also quantified the contributions of under-shoe fluid drainage to friction in NSR shoes. The coefficient of friction (ACOF) and under-shoe fluid pressures of fifteen NSR shoes were measured. A previously developed ACOF prediction model based on measurable outsole features was applied to the NSR shoes. The previously developed model did not apply well (in trends, as indicated by interaction effects involving SR/NSR classification, or in magnitude, p < 0.001) to NSR shoes. Instead, an increase in the fluid pressures were associated with a reduction in ACOF (p < 0.001). This study demonstrates that fluid pressures dominate performance in NSR shoes in contrast to SR shoes.

Safety Comes First: Novel Styrene Butadiene Rubber (SBR) and Ethylene Propylene Diene Monomer (EPDM) Surfaces as a Response to Sport Injuries

An athlete’s performance depends not only on the shoes they wear but also on the surface used in sports facilities. In addition, it can significantly contribute to reducing injuries, which are easy to get during sports competitions. In the present study, we wanted to investigate whether recycled styrene butadiene rubber (SBR) and ethylene propylene diene monomer (EPDM) could be used in the production of sports surfaces. For this purpose, we designed three different sports surfaces: (1) SBR covered with a thin EPDM spray layer on the top, (2) clean EPDM, and (3) bottom SBR layer with the top layer of EPDM. The test program of these surfaces included in its scope: shock absorption, vertical deformation, tensile strength, abrasion resistance, and slip resistance tests. Our research also involved the influence of the substrate under surface, temperature, and surface conditions. Presented results show that both materials, in the right proportions, can be used in the production of sports surfaces.

Comparative Analysis of Slip Resistance Test Methods for Granite Floors

This paper attempts to compare three methods of testing floor slip resistance and the resulting classifications. Polished, flamed, brushed, and grained granite slabs were tested. The acceptance angle values (α_ob) obtained through the shod ramp test, slip resistance value (SRV), and sliding friction coefficient (μ) were compared in terms of the correlation between the series, the precision of each method, and the classification results assigned to each of the three obtained indices. It was found that the evaluation of a product for slip resistance was strongly related to the test method used and the resulting classification method. This influence was particularly pronounced for low roughness slabs. This would result in risks associated with inadequate assessments, which could affect the safe use of buildings facilities.

Prediction of coefficient of friction based on footwear outsole features

Traction testing of footwear is expensive, which may create barriers for certain users to assess footwear. This study aimed to develop a statistical model that predicts available coefficient of friction (ACOF) under boundary lubrication conditions based on inexpensive measurements of footwear outsole features. Geometric and material hardness parameters were measured from fifty-eight footwear designs labeled as slip-resistant. A robotic friction measurement device was used to quantify ACOF with canola oil as the contaminant. Stepwise regression methods were used to develop models based on the outsole parameters and floor type to predict ACOF. The predictive ability of the regression models was tested using the k-fold cross-validation method. Results indicated that 87% of ACOF variation was explained by three shoe outsole parameters (tread surface area, heel shape, hardness) and floor type. This approach may provide an assessment tool for safety practitioners to assess footwear traction and improve workers' safety.

Breast Implant Surfaces and Their Impact on Current Practices: Where We Are Now and Where Are We Going?

Most commercially available breast implants feature some degree of elastomer surface modifications to increase surface roughness, in part because several clinical series have demonstrated positive outcomes from texturizing. However, the literature shows that textured implants support higher rates of bacterial growth, and there is a clear association between increased bacterial contamination and host response in vivo, such as capsular contracture. Furthermore, the infectious theory related to bacterial contamination has recently been described as a potential cause in the etiology of anaplastic large-cell lymphoma. Recent research has focused on the physiology of breast implant surfaces advances and how they interact with the body, creating new surface technologies which have the potential to affect all aspects of breast surgery. Understanding how surface properties affect inflammatory cell response will be essential in designing implants that can provide an esthetic solution while also minimizing long-term clinical complications. This special topic highlights the current knowledge on silicone implant surfaces, as well as innovations that have shaped and will continue to change the silicone breast implant industry in the future. It also provides an overview of the principal surfaces that exist and may find clinical applications in esthetic and reconstructive breast surgery. As additional advances emerge, objective tools will be required to evaluate the different surfaces available on the market, along with the long-term efficacy of new technologies.

Relationship among several measurements of slipperiness obtained in a laboratory environment

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.

Shoe-Floor Interactions in Human Walking With Slips: Modeling and Experiments

Shoe-floor interactions play a crucial role in determining the possibility of potential slip and fall during human walking. Biomechanical and tribological parameters influence the friction characteristics between the shoe sole and the floor and the existing work mainly focus on experimental studies. In this paper, we present modeling, analysis, and experiments to understand slip and force distributions between the shoe sole and floor surface during human walking. We present results for both soft and hard sole material. The computational approaches for slip and friction force distributions are presented using a spring-beam networks model. The model predictions match the experimentally observed sole deformations with large soft sole deformation at the beginning and the end stages of the stance, which indicates the increased risk for slip. The experiments confirm that both the previously reported required coefficient of friction (RCOF) and the deformation measurements in this study can be used to predict slip occurrence. Moreover, the deformation and force distribution results reported in this study provide further understanding and knowledge of slip initiation and termination under various biomechanical conditions.

Predictive multiscale computational model of shoe-floor coefficient of friction

Understanding the frictional interactions between the shoe and floor during walking is critical to prevention of slips and falls, particularly when contaminants are present. A multiscale finite element model of shoe-floor-contaminant friction was developed that takes into account the surface and material characteristics of the shoe and flooring in microscopic and macroscopic scales. The model calculates shoe-floor coefficient of friction (COF) in boundary lubrication regime where effects of adhesion friction and hydrodynamic pressures are negligible. The validity of model outputs was assessed by comparing model predictions to the experimental results from mechanical COF testing. The multiscale model estimates were linearly related to the experimental results (p < 0.0001). The model predicted 73% of variability in experimentally-measured shoe-floor-contaminant COF. The results demonstrate the potential of multiscale finite element modeling in aiding slip-resistant shoe and flooring design and reducing slip and fall injuries.

Nanotechnology, nanosurfaces and silicone gel breast implants: current aspects

Nanotechnology is defined as the design of products that interact with biological systems on the nanoscopic scale. Creating a controlled nanotexture and understanding the ways in which surface properties impact inflammatory response is of the utmost significance in designing implants that can provide satisfactory outcomes.

Slip safety risk analysis of surface properties using the coefficients of friction of rocks

This study was conducted to determine the most appropriate surface processing techniques (SPT), environmental conditions (EC) and surface roughness (SR) to minimize the risk of slipping when pedestrians walk on a floor covering of rocks barefoot and with shoes. Coefficients of friction (COFs) and values of SR were found using five different types of rocks, four SPT and two (ramp and pendulum) tests. Results indicate that the parameters which affect the COF values of rocks include SR, EC and SPT. Simple linear regression was performed to examine the relationship between the values of the COF and the SR. The value of the COF was identified as R² ≥ 0.864. Statistical results, which are based on experimental measurements, show that rocks are classified according to their safe use areas depending on their COF and SR values.

The Combined Benefits of Slip-Resistant Shoes and High Traction Flooring on Coefficient of Friction Exceeds Their Individual Contributions

High traction flooring and slip-resistant shoes are often used to reduce slip and fall accidents. However, the relative contribution and interactions across these parameters on available coefficient of friction (ACOF) are not well understood. The purpose of this study was to quantify the impact of flooring and slip-resistant shoes on ACOF. Seventeen shoes, five flooring tiles and three contaminants were tested using a robotic slip-tester, while ACOF was measured. ACOF was higher for slip-resistant shoes than not slip-resistant shoes. Larger effects were observed for shoe classification compared with flooring. Interaction effects indicated that the gap across shoe classifications was greater for the high ACOF floorings compared to the low ACOF floorings. This study suggests that the benefit of combining high traction flooring and slip-resistant shoes exceed the summed benefit of these factors and has the potential to reduce slipping events.

Investigation of Floor Surface Finishes for Optimal Slip Resistance Performance

Background

Increasing the slip resistance of floor surfaces would be desirable, but there is a lack of evidence on whether traction properties are linearly correlated with the topographic features of the floor surfaces or what scales of surface roughness are required to effectively control the slipperiness of floors.

Objective

This study expands on earlier findings on the effects of floor surface finishes against slip resistance performance and determines the operative ranges of floor surface roughness for optimal slip resistance controls under different risk levels of walking environments.

Methods

Dynamic friction tests were conducted among three shoes and nine floor specimens under wet and oily environments and compared with a soapy environment.

Results

The test results showed the significant effects of floor surface roughness on slip resistance performance against all the lubricated environments. Compared with the floor-type effect, the shoe-type effect on slip resistance performance was insignificant against the highly polluted environments. The study outcomes also indicated that the oily environment required rougher surface finishes than the wet and soapy ones in their lower boundary ranges of floor surface roughness.

Conclusion

The results of this study with previous findings confirm that floor surface finishes require different levels of surface coarseness for different types of environmental conditions to effectively manage slippery walking environments. Collected data on operative ranges of floor surface roughness seem to be a valuable tool to develop practical design information and standards for floor surface finishes to efficiently prevent pedestrian fall incidents.

Multidimensional Aspects of Slips and Falls

The study of slips and falls has traditionally focused on body kinematics and tribology. However, this strictly mechanical approach does not allow scientists to assess the importance of each component in relation to the complete system, and thus it lacks integration. The purpose of this chapter is to present and demonstrate the components of a broad analysis for in-depth understanding of slips and falls while walking on level surfaces. In most slip-and-fall studies, balance analysis is simplified and attributed to the point of heel contact. To determine sufficient fall prevention strategies, however, one must analyze balance before the critical moment of lost control. Such an approach requires the sciences of biomechanics, mechanics, anatomy, and neuromuscular control, as well as tribology. Causes of slips and falls are complex, and prevention approaches are often reactive, driven by high-injury trends and lawsuits. Prevention strategies need to be more proactive: Understanding the causes of accidents can help in identifying and correcting hazards before they cause problems. Examples include reporting incidents, selecting the right flooring, selecting footwear, and implementing proper floor-cleaning procedures. A combined effort among all members of the organization, including communication across the entire work system, is critical to the success of slip-and-fall prevention efforts.

State of science: occupational slips, trips and falls on the same level

Occupational slips, trips and falls on the same level (STFL) result in substantial injuries worldwide. This paper summarises the state of science regarding STFL, outlining relevant aspects of epidemiology, biomechanics, psychophysics, tribology, organisational influences and injury prevention. This review reaffirms that STFL remain a major cause of workplace injury and STFL prevention is a complex problem, requiring multi-disciplinary, multi-faceted approaches. Despite progress in recent decades in understanding the mechanisms involved in STFL, especially slipping, research leading to evidence-based prevention practices remains insufficient, given the problem scale. It is concluded that there is a pressing need to develop better fall prevention strategies using systems approaches conceptualising and addressing the factors involved in STFL, with considerations of the full range of factors and their interactions. There is also an urgent need for field trials of various fall prevention strategies to assess the effectiveness of different intervention components and their interactions. Practitioner Summary: Work-related slipping, tripping and falls on the same level are a major source of occupational injury. The causes are broadly understood, although more attention is needed from a systems perspective. Research has shown preventative action to be effective, but further studies are required to understand which aspects are most beneficial.

SURFACE MODIFICATION OF TPR SOLE: AN APPROACH TO IMPROVE SLIP RESISTANCE ON QUARRY AND CERAMIC TILES

Human slip on smooth surfaces is a common accident, even though the footwear soling materials are designed with cleats and treads to provide more friction with the floor. About 20% of footwear is made with thermoplastic rubber (TPR; styrene-butadiene-styrene) soles. The slip resistance property under wet-flooring conditions of this kind of sole is poor because of the nonionic nature of the polymer. Chemical surface modification can be exploited to improve the slip-resistance property of TPR soles. The surface is chemically modified with trichloroisocyanuric acid in a methyl ethyl ketone medium (TCI/MEK; at 1, 2, and 3%) to introduce chlorinated and oxidized moieties to the rubber surface. The extent of surface modification produced in TPR with this change can be tested using attenuated total reflectance–Fourier transform infrared spectroscopy, scanning electron microscopy, and contact angle and surface roughness measurements. The improvement in slip resistance can be evaluated by measuring the coefficient of friction using a dynamic slip-resistance tester. The extent of the change in the functional physical properties, such as surface roughness, contact angle, work adhesion, in slip resistance can be improved by optimizing the concentration of trichloroisocyanuric acid. Physicomechanical properties of unmodified and modified soles that are essential for wear performance can be tested and compared. Quantitative changes on the surface of modified rubber soles increases surface roughness, reduces contact angles, and increases work energy, so there is a considerable increase in the coefficient of friction, especially under wet floor conditions. The chemical surface treatment tends to reduce the bulk mechanical properties, such as tensile strength, elongation at break, and abrasion resistance, because cyanuric acid attacks the sole. The coefficient of friction produces a positive trend at 1 and 2% TCI/MEK treatments, but the trend is negative at a 3% concentration. The optimum surface treatment level for surface modification to enhance the slip resistance of TPR is 2% TCI/MEK.

Development of a high slip-resistant footwear outsole using a hybrid rubber surface pattern

The present study examined whether a new footwear outsole with tread blocks and a hybrid rubber surface pattern, composed of rough and smooth surfaces, could increase slip resistance and reduce the risk of fall while walking on a wet floor surface. A drag test was performed to measure static and dynamic coefficient of friction (SCOF and DCOF, respectively) values for the footwear with the hybrid rubber surface pattern outsole and two types of commercially available boots that are conventionally used in food factories and restaurant kitchens with respect to a stainless steel floor covered with glycerol solution. Gait trials were conducted with 14 participants who wore the footwear on the wet stainless steel floor. The drag test results indicated that the hybrid rubber surface pattern sole exhibited higher SCOF (≥0.44) and DCOF (≥0.39) values than the soles of the comparative footwear (p<0.001). Because of such high SCOF and DCOF values, the slip frequency (p<0.01), slip distance (p<0.001), and slip velocity (p<0.001) for the footwear with the hybrid rubber surface pattern outsole were significantly lower than those for the comparative footwear, which resulted in no falls during trials.

Fluid pressures at the shoe-floor-contaminant interface during slips: effects of tread and implications on slip severity

Previous research on slip and fall accidents has suggested that pressurized fluid between the shoe and floor is responsible for initiating slips yet this effect has not been verified experimentally. This study aimed to (1) measure hydrodynamic pressures during slipping for treaded and untreaded conditions; (2) determine the effects of fluid pressure on slip severity; and (3) quantify how fluid pressures vary with instantaneous resultant slipping speed, position on the shoe surface, and throughout the progression of the slip. Eighteen subjects walked on known dry and unexpected slippery floors, while wearing treaded and untreaded shoes. Fluid pressure sensors, embedded in the floor, recorded hydrodynamic pressures during slipping. The maximum fluid pressures (mean+/-standard deviation) were significantly higher for the untreaded conditions (124+/-75 kPa) than the treaded conditions (1.1+/-0.29 kPa). Maximum fluid pressures were positively correlated with peak slipping speed (r=0.87), suggesting that higher fluid pressures, which are associated with untreaded conditions, resulted in more severe slips. Instantaneous resultant slipping speed and position of sensor relative to the shoe sole and walking direction explained 41% of the fluid pressure variability. Fluid pressures were primarily observed for untreaded conditions. This study confirms that fluid pressures are relevant to slipping events, consistent with fluid dynamics theory (i.e. the Reynolds equation), and can be modified with shoe tread design. The results suggest that the occurrence and severity of unexpected slips can be reduced by designing shoes/floors that reduce underfoot fluid pressures.

Functional levels of floor surface roughness for the prevention of slips and falls: clean-and-dry and soapsuds-covered wet surfaces

Literature has shown a general trend that slip resistance performance improves with floor surface roughness. However, whether slip resistance properties are linearly correlated with surface topographies of the floors or what roughness levels are required for effective slip resistance performance still remain to be answered. This pilot study aimed to investigate slip resistance properties and identify functional levels of floor surface roughness for practical design applications in reducing the risk of slip and fall incidents. A theory model was proposed to characterize functional levels of surface roughness of floor surfaces by introducing a new concept of three distinctive zones. A series of dynamic friction tests were conducted using 3 shoes and 9 floor specimens under clean-and-dry as well as soapsuds-covered slippery wet environments. The results showed that all the tested floor-shoe combinations provided sufficient slip resistances performance under the clean-and-dry condition. A significant effect of floor type (surface roughness) on dynamic friction coefficient (DFC) was found in the soapsuds-covered wet condition. As compared to the surface roughness effects, the shoe-type effects were relatively small. Under the soapsuds-covered wet condition, floors with 50 μm in Ra roughness scale seemed to represent an upper bound in the functional range of floor surface roughness for slip resistance because further increase of surface roughness provided no additional benefit. A lower bound of the functional range for slip resistance under the soapsuds-covered wet condition was estimated from the requirement of DFC > 0.4 at Ra ≅ 17 μm. Findings from this study may have potential safety implications in the floor surface design for reducing slip and fall hazards.

A Novel Method for Evaluating the Effectiveness of Shoe-Tread Designs Relevant to Slip and Fall Accidents

Slip and falls account for a large share of occupational accidents. Slips are typically initiated when an insufficient amount of friction is present between the shoe and floor surfaces during walking. Shoe tread is thought to enhance the friction by channeling fluid contaminants away from the shoe and floor surface thus mitigating the fluid’s ability to lubricate the two surfaces and reduce friction. This study presents a novel method for evaluating the effectiveness of shoe tread by measuring fluid pressures during simulated slips. Sensors embedded into the floor measured fluid pressure while a robotic slip-tester simulated a human slip. A work shoe with three different tread depths (no, medium and full tread) was tested against a vinyl floor using a diluted (90%) glycerol and diluted detergent (2% detergent, 98% water) contaminant. Fluid pressures were high in the no tread condition but negligible in the other two tread depth conditions for the diluted glycerol and were negligible for all diluted detergent conditions. The no tread (COF: 0.005) also had lower friction coefficient values than treaded conditions (COF: 0.08-0.38). This study suggests that the effectiveness of tread to reduce the lubricating quality of the fluid can be directly measured using a robotic slip-tester and a fluid pressure sensor embedded in the floor. This method has the potential for developing tread depth recommendations and in evaluating the validity of slip-testers to simulate under-shoe conditions.

Linear regression models of floor surface parameters on friction between Neolite and quarry tiles

For slips and falls, friction is widely used as an indicator of surface slipperiness. Surface parameters, including surface roughness and waviness, were shown to influence friction by correlating individual surface parameters with the measured friction. A collective input from multiple surface parameters as a predictor of friction, however, could provide a broader perspective on the contributions from all the surface parameters evaluated. The objective of this study was to develop regression models between the surface parameters and measured friction. The dynamic friction was measured using three different mixtures of glycerol and water as contaminants. Various surface roughness and waviness parameters were measured using three different cut-off lengths. The regression models indicate that the selected surface parameters can predict the measured friction coefficient reliably in most of the glycerol concentrations and cut-off lengths evaluated. The results of the regression models were, in general, consistent with those obtained from the correlation between individual surface parameters and the measured friction in eight out of nine conditions evaluated in this experiment. A hierarchical regression model was further developed to evaluate the cumulative contributions of the surface parameters in the final iteration by adding these parameters to the regression model one at a time from the easiest to measure to the most difficult to measure and evaluating their impacts on the adjusted R(2) values. For practical purposes, the surface parameter R(a) alone would account for the majority of the measured friction even if it did not reach a statistically significant level in some of the regression models.

Impact of joint torques on heel acceleration at heel contact, a contributor to slips and falls

Slips/falls are a health burden in the workplace. Previous research has implied a relationship between foot dynamics at heel contact and slips/falls; however, heel acceleration has received little attention. Heel acceleration as the heel contacts the ground is the result of the combined effort of the leg joint torques to control motion of the foot. This study aims to examine the association of heel acceleration with fall risk, and explore the main joint torque determinant of heel acceleration at contact. Sixteen young and eleven older adults walked on known dry floors and in slippery environments expected to be dry. Heel acceleration at heel contact in the direction of motion, i.e. anterior/posterior, was compared between slip-recovery and slip-fall outcomes. Results showed that subjects that recovered contacted the floor with a greater heel deceleration (p < 0.05) than fall subjects. Knee torque alone explained 76% of the heel acceleration variability (p < 0.01). These data suggest that walking with reduced knee flexion torque at heel contact results in a reduced heel deceleration, a potential risk factor for slip-initiated falls.

Determination of coefficient of friction between the equine foot and different ground surfaces: an in vitro study

Slippery surfaces are a continuous concern in equine veterinary practice during both treatment and orthopaedic work-ups, especially when horses have to trot on circles. Sliding of the equine foot on the ground with the potential of injury is prevented if the horizontally acting accelerating or decelerating forces on the foot do not exceed maximal friction. Friction can be calculated and therefore anticipated if the coefficient of friction (μ) between the foot of the horse and the particular ground surface is known. Friction between shod and unshod cadaver equine hooves and different ground surfaces (concrete, tarmac and rubber) was determined by pulling the hooves horizontally in a uniform motion. Horizontal forces (Fh) were measured on a force plate and with a portable digital electronic force meter. The coefficient of friction (μ) was calculated as the quotient between Fh and the gravity force (N) of the object, hence: μ = Fh /N. This study has shown that the coefficient of friction between equine hooves and a specific ground surface can be determined using a portable digital force meter or a force plate. Friction significantly depended not only on the type of surface but also on shoeing of the equine foot. Bare feet showed more friction with the hard surfaces (bricks and tarmac), the shod feet showing more friction with the rubber surfaces. Coefficients of friction could be used to estimate the possibility of injuries occurring in the equine industry during exercise and/or lameness or pre-purchase examinations.

Effects of roughness and compressibility of flooring on cow locomotion

We examined the effects of roughness and degree of compressibility of flooring on the locomotion of dairy cows. We observed 16 cows walking down specially constructed walkways with materials that differed in surface roughness and degree of compressibility. Use of a commercially available soft rubber flooring material decreased slipping, number of strides, and time to traverse the corridor. These effects were most apparent at difficult sections of the corridor, such as at the start, at a right-angle turn, and across a gutter. Covering the walkway with a thin layer of slurry increased frequency of slipping, number of strides, and time taken to traverse the walkway. Effects of adding slurry were not overcome by increasing surface roughness or compressibility. Placing more compressible materials under a slip-resistant material reduced the time and number of steps needed to traverse the corridor but did not reduce slips, and the effects on cow locomotion varied nonlinearly with the degree of compressibility of the floor. Use of commercially available rubber floors improved cow locomotion compared with concrete floors. However, standard engineering measures of the floor properties may not predict effects of the floor on cow behavior well. Increasing compressibility of the flooring on which cows walk, independently of the roughness of the surface, can improve cow locomotion.

Nonfatal occupational injuries from slips, trips, and falls among older workers treated in hospital emergency departments, United States 1998

BACKGROUND

Falls are a leading cause of injury among older adults. As the workforce demographics shift to an older population, the dearth of information on occupational falls among older adults must be addressed.

METHODS

A national probability sample of hospital emergency departments (EDs) (National Electronic Injury Surveillance System) was utilized to characterize falls at work.

RESULTS

Older workers were found not to be at increased risk of a fall injury, but were more likely than younger workers to be hospitalized post-injury. Same-level falls were the most common type of incident among older workers. Falls from height were more prevalent among men than women. The narrative case descriptions for same-level falls to the floor primarily implicated floor contamination and tripping hazards.

CONCLUSIONS

Fall prevention programs targeted to older workers must examine extrinsic sources of falls, particularly surface traction, contaminant control, and footwear.

The effect of surface waviness on friction between Neolite and quarry tiles

Friction is widely used as an indicator of surface slipperiness in preventing accidents in slips and falls. Surface texture affects friction, but it is not clear which surface characteristics are better correlated with friction. Highly correlated surface characteristics could be used as potential interventions to prevent slip and fall accidents. The dynamic friction between quarry tiles and a commonly used sole testing material, Neolite, using three different mixtures of glycerol and water as contaminants at the interface was correlated with the surface parameters of the tile surfaces. The surface texture was quantified with various surface roughness and surface waviness parameters using three different cut-off lengths to filter the measured profiles for obtaining the profiles of either surface roughness or surface waviness. The correlation coefficients between the surface parameters and the measured friction were affected by the glycerol contents and cut-off lengths. Surface waviness parameters could potentially be better indicators of friction than commonly used surface roughness parameters, especially when they were measured with commonly used cut-off lengths or when the viscosity of the liquid contaminant was high.

Slip resistant properties of footwear on ice

Current research on slipperiness of footwear has mainly focused on floors and lubricated floors. Slips and falls on icy and snowy surfaces involve not only outdoor workers, but also pedestrians and the general public; and occur in cold regions and in winter season in many parts of the world. However, in comparison with the size of the problem, research on slips and falls on icy and snowy surfaces has been scarce. The objective of this paper is to explore the slip resistant properties of footwear (soling materials, roughness and hardness) on ice. The coefficients of kinetic friction of four different soling materials (synthetic rubber, nitrile rubber, natural rubber and polyurethane) were measured on ice (-12 degrees C). The outsole roughness and hardness were also measured. Results showed that the polyurethane soling did not perform better than synthetic rubber, nitrile rubber and natural rubber on pure hard ice (-12 degrees C). Soling roughness was positively correlated with the coefficient of kinetic friction. The most slip resistant soling material (polyurethane) on floors and lubricated floors may not provide sufficient slip resistance on ice.

A systems perspective of slip and fall accidents on icy and snowy surfaces

Current research on slips and falls has mainly focused on floors and/or contaminated floors. Although icy and snowy surfaces near melting temperature are more slippery, more important still, slip and falls on icy and snowy surfaces involve not only outdoor workers, but also pedestrians and the general public; and occur in cold regions and in the winter season in many parts of the world. However, in comparison with the size of the problem, research work done so far in this area has been limited. The objective of this paper is to present a systems perspective of slip and fall accidents, with special focus on its occurrence on icy and snowy surfaces. In order to explore the aetiology of slip and fall accidents further, and to provide the basis for prevention, the authors put forward a systems model towards the slips and falls on icy and snowy surfaces based on a review of literature and current knowledge. Various contributing factors are systematically discussed to highlight the multi-factorial nature of the problem, providing the possibility of a multi-faceted approach to reach systematic prevention. Unresolved issues related to slips and falls on ice and snow are also identified, which necessitate further research.

Preferred surface microscopic geometric features on floors as potential interventions for slip and fall accidents on liquid contaminated surfaces

PROBLEM

Surface roughness affects friction, so selection of floor surfaces with certain roughness characteristics could potentially reduce slip and fall accidents. This article summarizes the preferred surface microscopic geometric features that could increase friction on surfaces covered with liquid contaminants.

METHOD

Three types of surface features, represented by the average of the maximum height above the mean line in each cut-off length (R(pm)), the arithmetical average of surface slope (Delta(a)), and the kernel roughness depth (R(k)), are identified as preferred surface microscopic geometric features for a higher friction. The proper settings on the profilometers (instruments used to measure surface roughness) for optimizing these surface parameters are specified. The friction mechanisms involved reveal why these features are more desirable.

RESULTS

Although surface roughness is important in determining slipperiness, there is still insufficient information to establish a safety criterion based on roughness; however, the method presented in this paper can readily provide a relative comparison.

IMPACT ON INDUSTRY

The summary presented will help safety professionals properly select new floor surfaces or assess existing floors to reduce slip and fall accidents.

Measurement of slipperiness: fundamental concepts and definitions

The main objective of this paper is to give an overview of basic concepts and definitions of terms related to the 'measurement of slipperiness' from the onset of a foot slide to a gradual loss of balance and a fall. Other unforeseen events prior to falls (e.g. tripping) are sparingly dealt with. The measurement of slipperiness may simply comprise an estimation of slipping hazard exposures that initiate the chain of events ultimately causing an injury. However, there is also a need to consider the human capacity to anticipate slipperiness and adapt to unsafe environments for avoiding a loss of balance and an injury. Biomechanical and human-centred measurements may be utilized for such an approach, including an evaluation of relevant safety criteria for slip/fall avoidance and procedures for validation of slip test devices. Mechanical slip testing approaches have been readily utilized to measure slipperiness in terms of friction or slip resistance but with conflicting outcomes. An improved understanding of the measurement of slipperiness paradigm seems to involve an integration of the methodologies used in several disciplines, among others, injury epidemiology, psychophysics, biomechanics, motor control, materials science and tribology.

Biomechanics of slips

The biomechanics of slips are an important component in the prevention of fall-related injuries. The purpose of this paper is to review the available literature on the biomechanics of gait relevant to slips. This knowledge can be used to develop slip resistance testing methodologies and to determine critical differences in human behaviour between slips leading to recovery and those resulting in falls. Ground reaction forces at the shoe-floor interface have been extensively studied and are probably the most critical biomechanical factor in slips. The ratio of the shear to normal foot forces generated during gait, known as the required coefficient of friction (RCOF) during normal locomotion on dry surfaces or 'friction used/achievable' during slips, has been one biomechanical variable most closely associated with the measured frictional properties of the shoe/floor interface (usually the coefficient of friction or COF). Other biomechanical factors that also play an important role are the kinematics of the foot at heel contact and human responses to slipping perturbations, often evident in the moments generated at the lower extremity joints and postural adaptations. In addition, it must be realized that the biomechanics are dependent upon the capabilities of the postural control system, the mental set of the individual, and the perception of the environment, particularly, the danger of slipping. The focus of this paper is to review what is known regarding the kinematics and kinetics of walking on surfaces under a variety of environmental conditions. Finally, we discuss future biomechanical research needs to help to improve walkway-friction measurements and safety.

The measurement of slipperiness--an international scientific symposium

Occupational slips, trips, and falls (STF) present a tremendous burden on the working people of the world. The precise contribution of slipping to this burden is not completely understood and significant questions exist regarding the definition and measurement of slipperiness. In an attempt to advance slipperiness measurement, a workshop symposium of tribologists, biomechanists, clinicians, engineers, epidemiologists and related scientists was held in order to summarize the state of the science in slipperiness measurement. Organized into issue-focused working groups, participants collaborated on manuscripts addressing conceptual and definitional issues, the contribution of slipperiness to STF injury, and biomechanical, human-centred, and tribological approaches to slipperiness measurement. The conference design, contributions of working groups and outcomes are summarized.