Floor/shoe slip resistance measurement

A Method for Accessing the Non-Slip Function of Socks in an Acute Maneuver

The shoe upper hides the foot motion on the insole, so it has been challenging to measure the non-slip function of socks in a dynamic motor task. The study aimed to propose a method to estimate the non-slip function of socks in an acute maneuver. Participants performed a shuttle run task while wearing three types of socks with different frictional properties. The forces produced by foot movement on the upper during the task were measured by pressure sensors installed at the upper. A force platform was also used to measure the ground reaction force at the outsole and ground. Peak force and impulse values computed by using forces measured by the pressure sensors were significantly different between the sock conditions, while there were no such differences in those values computed by using ground reaction forces measured by a force platform. The results suggested that the non-slip function of socks could be quantified by measuring forces at the foot-upper interface. The method could be an affordable option to measure the non-slip function of socks with minimal effects from skin artifacts and shoe upper integrity.

A Novel Method to Measure the Static Coefficient of Friction for Socks

Mechanical testers have commonly been used to measure the frictional properties of socks. However, the friction values may be susceptible to the level of stretchiness of tested fabrics or human variability. Thus, the aim of this study was to propose a novel method that enables friction measurement of socks in a sock-wearing condition with less human variability effects. Five socks with different frictional properties were chosen. Three experimental ramp tests were performed with an artificial structure shaped like the foot-ankle complex (last) and a ramp tester to quantify the static coefficient of friction (COF) at the foot against sock, at the sock against an insole, and the foot wearing socks against the insole, respectively. The angle where the last slipped while the ramp surface was gradually inclined was used to compute the static COF values for each sock. The reliability was 0.99, and COF values ranged from 0.271 to 0.861 at the foot-sock interface, 0.342 to 0.639 at the sock-insole interface, and 0.310 to 0.614 in the third test. Socks with different frictional properties were successfully distinguished each other. Thus, the suggested protocol could be a reliable option for measuring the static COF values in the tension similar with it found in a sock-waring condition with reduced effects of human variability.

Does the shoe really fit? Characterising ill-fitting footwear among community-dwelling older adults attending geriatric services: an observational cross-sectional study

Background

Falls in older people are common and can result in loss of confidence, fear of falling, restriction in activity and loss of independence. Causes of falls are multi-factorial. There is a paucity of research assessing the footwear characteristics among older people who are at high risk of falls, internationally and in the Irish setting. The aim of this study was to examine the proportion of older adults attending a geriatric day hospital in Ireland who were wearing incorrectly sized shoes.

Methods

A consecutive sample of 111 older adults aged 60 years and over attending a geriatric day hospital in a large Irish teaching hospital was recruited. Demographic data including age, mobility, medications, co-habitation status, footwear worn at home and falls history were recorded. Shoe size and foot length were measured in millimetres using an internal shoe gauge and SATRA shoe size stick, respectively. Participants’ self-reported shoe size was recorded. Footwear was assessed using the Footwear Assessment Form (FAF). A Timed Up and Go (TUG) score was recorded. Functional independence was assessed using the Nottingham Extended Activities of Daily Living (NEADL) Scale. The primary outcome of interest in this study was selected as having footwear within the suggested range (10 to 15 mm) on at least one foot. Participants who met this definition were compared to those with ill-fitting footwear on both feet using Chi-square tests, T-tests or Mann–Whitney U tests.

Results

The mean difference between shoe length and foot length was 18.6 mm (SD: 9.6 mm). Overall, 72% of participants were wearing footwear that did not fit correctly on both feet, 90% had shoes with smooth, partly worn or fully worn sole treading and 67% reported wearing slippers at home. Participant age, TUG score and NEADL score were not associated with ill-fitting footwear.

Conclusions

Wearing incorrectly fitting shoes and shoes with unsafe features was common among older adults attending geriatric day services in this study. A large number of participants reported wearing slippers at home.

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.

Effect of a powered drive on pushing and pulling forces when transporting bariatric hospital beds

Powered drives designed to assist with moving hospital beds are commercially available but no studies have evaluated whether they reduce the push and pull forces likely contributing to injury in caregivers. This study measured hand forces of 10 caregivers maneuvering a manual and powered bariatric bed through simulated hospital environments (hallway, elevator, and ramp). Peak push and pull forces exceeded previously established psychophysical limits for all activities with the manual bed. For the powered bed, peak forces were significantly (p < 0.05) lower for all tasks, and below psychophysical limits. Powered drive reduced peak forces between 38% (maneuvering into elevator) and 94% (descending ramp). Powered drive also reduced stopping distance by 55%. When maneuvering, the integral of hand force was 34% lower with powered drive, but average forces during straight-line pushing did not differ between beds. Powered drive may reduce the risk of injury or the number of caregivers needed for transport.

Nurses' understandings of suitable footwear for older people

PURPOSE

The purpose of this paper is to gain insight into nurses' understandings of what constitutes suitable footwear for older people in care homes.

DESIGN/METHODOLOGY/APPROACH

An exploratory descriptive qualitative survey was carried out of 20 registered nurses employed in six Scottish care homes for older people. Data were collected using a semi-structured questionnaire that included five open-ended questions. Content analysis was used to theme footwear perceptions.

FINDINGS

Participants had several views about what encompasses safe footwear; some were erroneous. The link between inappropriate footwear and falls was recognised by 80 per cent of respondents, but some were unclear about the features that effect or inhibit safety. No UK or international standardised guidelines were identified that advise nurses about appropriate footwear for older people.

PRACTICAL IMPLICATIONS

It is unknown whether respondents represent the nurse population because findings are restricted by a small sample size. Nonetheless, the group showed variable understanding of what constitutes safe footwear for older people and links with fall prevention. Improved nurse-education about what comprises safe footwear and the links with falls prevention in older people is required. Structured guidelines to direct nurse educators about what to teach student nurses about appropriate footwear for older people may work towards reducing falls.

ORIGINALITY/VALUE

No guidelines to direct nurses about appropriate footwear for older people in care homes have been written. Key points have been developed.

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.

The influence of footwear sole hardness on slip characteristics and slip-induced falls in young adults

Theoretically, a shoe that provides less friction could result in a greater slip distance and foot slipping velocity, thereby increasing the likelihood of falling. The purpose of this study was to investigate the effects of sole hardness on the probability of slip-induced falls. Forty young adults were randomized into a hard or a soft sole shoe group, and tested under both nonslippery and slippery floor conditions using a motion analysis system. The proportions of fall events in the hard- and soft-soled shoe groups were not statistically different. No differences were observed between shoe groups for average slip distance, peak and average heel velocity, and center of mass slipping velocity. A strong association was found between slip distance and the fall probability. Our results demonstrate that the probability of a slip-induced fall was not influenced by shoe hardness. Once a slip is induced, slip distance was the primary predictor of a slip-induced fall.

Increased shoe sole hardness results in compensatory changes in the utilized coefficient of friction during walking

Based on mechanical testing, harder soled shoes have been shown to provide less available friction than soft soled shoes. Whether or not humans adjust their utilized coefficient of friction (COFu) and gait kinematics to accommodate the decrease in available friction while wearing hard soled shoes is not known. Fifty-six young adults participated in this study. Ground reaction forces, full body kinematics, stride characteristics and subjective perception of footwear slipperiness were recorded under both hard and soft soled shoe conditions. Paired t-tests were used to identify the differences between two shoes conditions. Results indicated that the peak COFu was significantly less when wearing the hard soled shoes compared to when wearing the soft soled shoes (0.23 vs. 0.26, P<0.001). The decrease in peak COFu was the result of a decrease in the resultant shear forces at the time of peak COFu as no difference in the vertical ground reaction forces was observed. When wearing hard soled shoes, subjects demonstrated decreased total body center of mass (COM) acceleration prior to and immediately following initial contact, decreased walking velocity, shortened stride length, and reduced ankle dorsiflexion angle at initial contact. Taken together, we believe that these gait modifications represent behavioral adaptations to wearing shoes that are perceived to be more slippery.

The effects of usual footwear on balance amongst elderly women attending a day hospital

OBJECTIVE

to examine the effects of footwear on balance in a sample of older women attending a day hospital.

DESIGN

this was a crossover trial with a quasi-randomised allocation.

SETTING

assessments took place in the geriatric day hospital.

SUBJECTS

a cohort of 100 older women aged 60 years and over attending a day hospital.

METHODS

demographic data and a brief falls history were recorded. Participant's footwear was assessed using a footwear assessment form. A Berg Balance Scale (BBS) was completed under two conditions--shoes on and shoes off with order counter-balanced.

RESULTS

the mean BBS was 39.07 (SD 9.14) with shoes on and 36.54 (SD 10.39) with shoes off (P < 0.0001). Balance scores were significantly higher with shoes on for 10 of the 14 Berg subcategories. Lower barefoot BBS scores were associated with a greater beneficial effect of footwear on balance (P < 0.001). Shoe characteristics were not associated with change in the BBS score.

CONCLUSIONS

Wearing their own footwear significantly improved participants' balance compared to being barefoot. The greatest benefit of footwear was seen in those with the poorest balance. Further studies should investigate whether particular types of footwear are associated with greater benefit.

Research on slip resistance measurements--a new challenge

Slips, trips and falls are one of the most common causes of injuries and fatalities in the general community and industry. The control of such incidents involves a complex array of factors including the characteristics of each individual's footwear and gait dynamics, walking and working surfaces, and environmental conditions. Notwithstanding this complexity, slip resistance properties have been widely measured as a form of coefficient of friction (COF) index at the sliding interface between the shoes and floors. Since the COF measurements were commonly adopted to evaluate slip potentials, it has been found that there were controversies in the interpretation of COF measurement results. This study, therefore, was principally focused on broadening the knowledge base and developing new ideas on which improvements in the validity and reliability of slip resistance measurements might be made. To achieve this goal, crucial problems on the current concept of slip resistance measurement were extensively analysed by a tribological point of view where principle understanding of the shoe-floor friction and wear phenomena could be made. Based on this approach, new theoretical models were suggested.

An integrated approach towards identifying age-related mechanisms of slip initiated falls

The causes of slip and fall accidents, both in terms of extrinsic and intrinsic factors and their associations are not yet fully understood. Successful intervention solutions for reducing slip and fall accidents require a more complete understanding of the mechanisms involved. Before effective fall prevention strategies can be put into practice, it is central to examine the chain of events in an accident, comprising the exposure to hazards, initiation of events and the final outcome leading to injury and disability. These events can be effectively identified and analyzed by applying epidemiological, psychophysical, biomechanical and tribological research principles and methodologies. In this manuscript, various methods available to examine fall accidents and their underlying mechanisms are presented to provide a comprehensive array of information to help pinpoint the needs and requirements of new interventions aimed at reducing the risk of falls among the growing elderly population.

Effects of aging on the biomechanics of slips and falls

Although much has been learned in recent decades about the deterioration of muscular strength, gait adaptations, and sensory degradation among older adults, little is known about how these intrinsic changes affect biomechanical parameters associated with slip-induced fall accidents. In general, the objective of this laboratory study was to investigate the process of initiation, detection, and recovery of inadvertent slips and falls. We examined the initiation of and recovery from foot slips among three age groups utilizing biomechanical parameters, muscle strength, and sensory measurements. Forty-two young, middle-age, and older participants walked around a walking track at a comfortable pace. Slippery floor surfaces were placed on the track over force platforms at random intervals without the participants' awareness. Results indicated that younger participants slipped as often as the older participants, suggesting that the likelihood of slip initiation is similar across all age groups; however, older individuals' recovery process was much slower and less effective. The ability to successfully recover from a slip (thus preventing a fall) is believed to be affected by lower extremity muscle strength and sensory degradation among older individuals. Results from this research can help pinpoint possible intervention strategies for improving dynamic equilibrium among older adults.

Footwear style and risk of falls in older adults

OBJECTIVES

To determine how the risk of a fall in an older adult varies in relation to style of footwear worn.

DESIGN

Nested case-control study.

SETTING

Group Health Cooperative, a large health maintenance organization in Washington state.

PARTICIPANTS

A total of 1,371 adults aged 65 and older were monitored for falls over a 2-year period; 327 qualifying fall cases were compared with 327 controls matched on age and sex.

MEASUREMENTS

Standardized in-person examinations before fall occurrence, interviews about fall risk factors after the fall occurred, and direct examination of footwear were conducted. Questions for controls referred to the last time they engaged in an activity broadly similar to what the case was doing at the time of the fall.

RESULTS

Athletic and canvas shoes (sneakers) were the styles of footwear associated with lowest risk of a fall. Going barefoot or in stocking feet was associated with sharply increased risk, even after controlling for measures of health status (adjusted odds ratio=11.2, 95% confidence interval (CI)=2.4-51.8). Relative to athletic/canvas shoes, other footwear was associated with a 1.3-fold increase in the risk of a fall (95% CI=0.9-1.9), varying somewhat by style.

CONCLUSION

Contrary to findings from gait-laboratory studies, athletic shoes were associated with relatively low risk of a fall in older adults during everyday activities. Fall risk was markedly increased when participants were not wearing shoes.

Development of a portable test device for assessing on-site floor slipperiness: an interim report

The main objective was to design and construct a prototype portable slipmeter with the capability of measuring static, transitional kinetic and steady-state kinetic coefficient of friction properties of on-site floors. The second objective was to evaluate its operation in the laboratory, using a commercial force platform as reference. The prototype was found to be capable of measuring the described frictional characteristics of floor surfaces, using three different test wheels and two modes of operation, impact and non-impact testing. The results anticipate that the slipmeter may prove to be more valid than any traditional measurement technique. The study continues with biomechanical trials and will be completed during the year 2000.

Center of mass velocity-position predictions for balance control

The purposes of this analysis were to predict the feasible movements during which balance can be maintained, based on environmental (contact force), anatomical (foot geometry), and physiological (muscle strength) constraints, and to identify the role of each constraint in limiting movement. An inverted pendulum model with a foot segment was used with an optimization algorithm to determine the set of feasible center of mass (CM) velocity-position combinations for movement termination. The upper boundary of the resulting feasible region ran from a velocity of 1.1 s-1 (normalized to body height) at 2.4 foot lengths behind the heel, to 0.45 s-1 over the heel, to zero over the toe, and the lower boundary from a velocity of 0.9 s-1 at 2.7 foot lengths behind the heel, to zero over the heel. Forward falls would be initiated if states exceeded the upper boundary, and backward falls would be initiated if the states fell below the lower boundary. Under normal conditions, the constraint on the size of the base of support (BOS) determined the upper and lower boundaries of the feasible region. However, friction and strength did limit the feasible region when friction levels were less than 0.82, when dorsiflexion was reduced more than 51%, or when plantar flexion strength was reduced more than 35%. These findings expand the long-held concept that balance is based on CM position limits (i.e. the horizontal CM position has to be confined within the BOS to guarantee stable standing) to a concept based on CM velocity-position limits.