Kai Way Li

Friction between foot and floor under barefoot conditions: A pilot study

An experiment was conducted in the laboratory to measure the force plate-based coefficient of friction (COF) between the foot and floor. A female human subject participated in the study. She was sitting with her thigh horizontal and her shank was in a vertical position. Her foot was on a tested floor which was mounted on a Bertec® 4060 force platform in front of her. There were four types of floors and three floor surface conditions. The subject slide her foot with either fast or slow sliding speed using either her left or right foot. The force plate-based COF between the foot and floor was calculated. The results found that the floor, surface condition, and sliding speed were all significant factors affecting the force plate-based COF. The surface condition was the most significant factor among all the factors considered in this study. The difference between the left and right foot was not significant.

Relationship between floor-type gait adaptations and required coefficient of friction

A gait experiment was conducted. Female subjects were requested to walk, with or without shoes, on a walkway at 2.5 km/hr. Four floors and three surface conditions were tested. The ground reaction forces were collected using a force platform. The required coefficient of friction (RCOF) was calculated. The peak RCOF was analyzed. The results indicated that the floor, surface, and shod conditions were all significant factors affecting the RCOF. The interaction effects of the shod × floor were also significant. The RCOF for the barefoot conditions was significantly lower than that of the shod conditions. The multiple comparison test results indicated that ceramic and steel floors had both significantly higher RCOF than those of the vinyl and wood floors. For surface conditions, dry surface had significantly the highest RCOF among all surfaces. The RCOF on the wet surfaces were significantly higher than that on the glycerol contaminated surfaces.

A study of combined manual materials handling tasks under footwear and lifting and lowering height conditions

A study on combined manual materials handling tasks performed on floors under three footwear and four lifting and lowering height conditions. Twelve male subjects participated in the study. The maximum acceptable weight of handling, including lifting, carrying for 3 m, lowering, and walking 3 m back at 2 per minute was determined. The subject then performed the same tasks for 10 minutes. The VO2, heart rate, and rating of perceived exertion for whole body strain were measured. The results showed that the effects of footwear on the maximum acceptable weights of handling (MAWH), heart rate, and VO2 were not significant. The effects of lifting and lowering height on all dependent variables except rating of perceived exertion were statistically significant (p≤0.027). Lifting from the floor and lowering on the floor condition was the most stressful condition than all other lifting and lowering condition. The subjects had the lowest MAWH on this condition. In addition, lifting from the floor and lowering on the floor condition resulted in the highest physiological responses including both VO2 and heart rate. The effects of lifting and lowering height on RPE was, however, not significant. The implication of this study was that lifting and lowering height should be regarded as one of the major job factors in designing MMH tasks as it affected physiological responses of the subjects. This is consistent with the findings in the literature.

A comparison of friction measurement results using two slipmeters

Assessment of floor slip slipperiness is of paramount importance in quantifying the risk of slipping and falling incidents. Friction measurement is one of the major approaches in assessing floor slipperiness. The Brungraber Mark II is one of the slipmeters commonly used in the USA. Operation of the Mark II requires repetitive strikes of the footwear pad on the floor for a single reading. One of the disadvantages of the Mark II is that the operator needs to lift a 4.54 kg weight and releases it with an awkward kneeing posture for every trial. To remedy this drawback, the designer of Mark II has fabricated a new slipmeter named Mark III. Instead of been driven by a 4.54 kg weight, the Mark III is activated by a spring. This requires less physical effort in both carrying and operating as compared to that of the Mark II. However, there is no published data examining the reliability and consistency of this new device. In this study, we compare the friction measurement results of the two slipmeters under four floors, four footwear materials, and three surface conditions.

Variation of friction coefficient of floors under five liquid contamination conditions for prevention of slip & fall injuries in restaurants

Slip and fall is one of the main occupational health and safety problems. If the floor is contaminated with fluids, its slip resistance would be reduced. In the working environment and in our daily life, the floors in kitchens of restaurants are commonly contaminated by various liquids and are often slippery. This research examined the effects of five commonly encountered liquids in kitchens on the coefficient of friction on the floor. The Brungraber Mark II friction measurement device was used. The Brookfield DVI-PRIME viscometer was used to measure the viscosities of the tested liquids. The research results show footwear sample, liquid and their interactions all had significant effects on the coefficient of friction. The higher the viscosity of the liquid, the lower the coefficient of friction was. Treaded Neolite had higher coefficient of friction than flat Neolite under all liquid contaminated conditions.

An analysis of floor roughness & slip resistance of floors

Slip and fall are the main cause of occupational injuries or fatalities at workplace. Falls have been one of the top three occupational incidences which reached a peak in 2013 with an incidence percentage of 17% in Taiwan. Most falls were attributed to unsafe environment where the floors were contaminated by the water and other liquids. This research was focused on the relationship between floor slip resistance and floor roughness. The coefficient of friction (COF) of 13 floors under four floor contaminated conditions were measured using two footwear pads. An English XL friction measurement device was adopted. The results showed that floors roughness, footwear sample, and floor surface condition are all significant factors affecting the COF. All the floors with Ra more than 25 μm had COF values higher than 0.5 when measured using the flat footwear pad.

Anthropometric Measures and Static Muscular Strengths for Youths Males and Females

Teenagers are in a growth spurt both in body dimensions and in physical strength. Isometric strength is commonly adopted to indicate the physical capability of humans to perform manual tasks. This study presents the data collected from 120 adolescences concerning their anthropometric measures and four isometric strengths. Both youth males and females, aged 13 to 15 years old, were recruited for measurements. The results of the study indicated that all the four strength were significantly (p<;0.05) affected by age and gender. Among the four strengths, isometric back strength was significantly (p<;0.05) the highest, next with the isometric leg strength, and next the isometric shoulder strength, and finally the isometric arm strength. The 15 years old subjects had significantly the highest isometric strengths than the other two age groups. It was found that the isometric strengths for female subjects were approximately two third of those of the male subjects. The Pearsons correlation coefficients between the variables were calculated. Stature and body weight were found to be the two most significant parameters related to the isometric strengths of the subjects. These strength data are valuable for designs not only in manual handling tasks but also in the facilities involving physical activities for teenagers.

Subjective rating of floor slipperiness & slip/fall outcomes in a gait experiment

Slips and falls create major burdens for both the industries and our society. A gait experiment was conducted in this study. The subject walked on a 6 m walkway with or without shoes and stepped on a tested area. The tested area was covered with one of the four floors: steel, wood, vinyl, and ceramic. The surface of the tested area might be dry, wet, or oily-contaminated. The subjective rating of floor slipperiness on the testing area was collected after the walk. The outcome of a trial was also recorded as without slip/fall, slipped without fall, or slipped and fall. It was found that the subjective ratings of floor slipperiness between the barefoot condition and shod condition were statistically significantly (p<;0.0001) on both dry and oily floors. Chi-square homogeneity tests on the outcome of slip/fall were performed. The results showed that the distribution of slip/fall outcomes were associated with the with/without shoes conditions. More slipped and fall cases were observed when the subjects were barefooted.

Guided grip force of the dominant hand for male subjects

Subjective rating has been adopted in quantifying the physical exertion in industrial works. In this study, an experiment was conducted to measure the grip force of twenty, male subjects under guided-gripping scenario. The subjects were requested to apply a power grip force with one of the four exertion levels towards their maximum voluntary contraction (MVC) using their dominant hands. The analysis of variance was conducted to test the variations of the grip forces among different level of force exertion. The results were statistically significant (p<0.0001). A linear regression model was established to describe the relationship between the gripping force and the perceived hand exertion based on the Borgs CR-10 scale. This model was statistically significant at p<0.0001 and with an R2 of 0.9. The Pearsons correlation coefficient between the grip force and the rating of the CR-10 scale was 0.95. The results of this study showed that the guided grip force of the dominant hand of the male subjects had linear relationship with the ratings of CR-10 scale. Therefore, the CR-10 scale is appropriate as a quantitative measure of perceived hand grip exertion of the dominant hand for males.

Friction measurements on inclined dry, wet, and glycerol-contaminated floors using four footwear samples

Slips and falls are very common not only in industry but also in our daily activities. The coefficient of friction (COF) is coomonly adopted as a measure to quantify floor slipperiness and as an index to represent the risk of slipping and falling. A friction measurement study was conducted in the laboratory under four footwear, three surface, and three inclination conditions. The Brungraber Mark II slipmeter was used for the measurement. The results showed that all the main and interaction effects of the three factors were statistically significant. Dry floors had the highest COF, next with the wet floor, and finally the glycerol contaminated floors. The flat floor had the highest COF, next with the 5° floors, and finally the 10° ones. Treaded Neolite had better slip-resistance than flat Neolite. Treaded rubber, however, did not provided batter slip-resistance than that of the flat rubber sample.