Traction performance across the life of slip-resistant footwear: Preliminary results from a longitudinal study.

INTRODUCTION: Slips, trips, and falls are a major cause of injury in the workplace. Footwear is an important factor in preventing slips. Furthermore, traction performance (friction and under-shoe fluid drainage) are believed to change throughout the life of footwear. However, a paucity of data is available for how traction performance changes for naturally worn, slip-resistant footwear. METHOD: The presented research is a preliminary analysis from an ongoing, larger study. Participants wore slip-resistant footwear while their distance walked was monitored. Friction and under-shoe fluid pressures were measured using a robotic slip tester under a diluted glycerol contaminant condition after each month of wear for the left and right shoes. The size of the worn region was also measured. RESULTS: Friction initially increased and then steadily decreased as the distance walked and the size of the worn region increased. Fluid pressures increased as the shoes were worn and were associated with increased walking distance and size of the worn region. DISCUSSION: Consistent with previous research, increases in the size of the worn region are associated with increased under-shoe fluid pressures and decreased traction. These trends are presumably due to reduced fluid drainage between the shoe-floor interface when the shoe becomes worn. CONCLUSIONS: Traction performance changes with natural wear. The distance walked in the shoe and the size of the worn region may be valuable indicators for assessing loss of traction performance. Practical Applications: Current shoe replacement recommendations for slip-resistant shoes are based upon age and tread depth. This study suggests that tools measuring the size of the worn region and/or distance traveled in the shoes are appropriate alternatives for tracking traction performance loss due to shoe wear.

An observational ergonomic tool for assessing the worn condition of slip-resistant shoes.

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.

Worn region size of shoe outsole impacts human slips: Testing a mechanistic model.

Shoe outsole tread wear has been shown to increase slip risk by reducing the tread's ability to channel fluid away from the shoe-floor interface. This study establishes a connection between geometric features of the worn region size and slipping. A mechanistic pathway that describes the relationship between the worn region size and slip risk is assessed. Specifically, it is hypothesized that an increased worn region size leads to an increase in under-shoe fluid pressure, which reduces friction, and subsequently increases slipping. The worn region size, fluid pressure, and slip outcome were recorded for 57 participants, who were exposed to an unexpected slip condition. Shoes were collected from each participant and the available coefficient of friction (ACOF) was measured using a tribometer. A greater shoe worn region size was associated with increased slip occurrence. Specifically, a 1 mm increase in the characteristic length of the worn region (geometric mean of its width and length) was associated with an increase in slip risk of ~10%. Fluid pressure and ACOF results supported the mechanistic model: an increase in worn region size correlated with an increase in peak fluid pressure; peak fluid pressures negatively correlated with ACOF; and increased ACOF correlated with decreased slip risk. This finding supports the use of worn region size as a metric to assess the risk of slipping.

Changes in under-shoe traction and fluid drainage for progressively worn shoe tread.

Shoe wear is known to increase slipping risk, but few studies have systematically studied this relationship. This study investigated the impact of progressive shoe wear on the available coefficient of friction (ACOF) and under-shoe fluid dynamics. Five different slip-resistant shoes were progressively worn using an accelerated, abrasive, wear protocol. The ACOF and fluid forces (the load supported by the fluid) were measured as shoes were slipped across a surface contaminated with a diluted glycerol solution. As the shoes became worn, an initial increase in ACOF was followed by a steady decrease. Low fluid forces were observed prior to wear followed by increased fluid forces as the worn region became larger. Results suggest that traction performance decreases particularly when the heel region without tread exceeds a size of 800 mm2. This study supports the concept of developing shoe replacement guidelines based upon the size of the worn region to reduce occupational slips.

Interpreting MSHA citations through the lens of occupational health and safety management systems: investigating their impact on mine injuries and illnesses 2003-2010.

Since the late 1980s, the U.S. Department of Labor has considered regulating a systems approach to occupational health and safety management. Recently, a health and safety management systems (HSMS) standard has returned to the regulatory agenda of both the Occupational Safety and Health Administration (OSHA) and the Mine Safety and Health Administration (MSHA). Because a mandated standard has implications for both industry and regulating bodies alike, it is imperative to gain a greater understanding of the potential effects that an HSMS regulatory approach can have on establishment-level injuries and illnesses. Through the lens of MSHA's regulatory framework, we first explore how current enforcement activities align with HSMS elements. Using MSHA data for the years 2003-2010, we then analyze the relationship between various types of enforcement activities (e.g., total number of citations, total penalty amount, and HSMS-aligned citations) and mine reportable injuries. Our findings show that the reduction in mine reportable injuries predicted by increases in MSHA enforcement ranges from negligible to 18%. The results suggest that the type and focus of the enforcement activity may be more important for accident reduction than the total number of citations issued and the associated penalty amount.

Ergonomic hand tool and desk and chair development process.

This paper suggests a practical and simple process consisting of 8 stages: needs assessment, ergonomics guidelines, anthropometry, brainstorming and idea sketch, preliminary model, drafting and rendering, working prototype, and user trials. The feasibility of this process was verified with the development of a modified clamping hand tool and a new student desk and chair. The case studies showed how design difficulties were overcome by integrating ergonomics guidelines in the process.

Biomechanical and physiological analyses of a luggage-pulling task.

The purpose of this study was to identify the degree of physical stresses on two-wheeled carry-on luggage users in terms of biomechanics and work physiology. Based on 3D kinematics, a 3D inverse dynamic biomechanical model having fifteen segments was developed to evaluate a one-hand pulling task. Joint reaction forces, joint moments and physiological variables (energy expenditure and heart rate) were measured from four subjects who performed 32 luggage-pulling tasks on a doublewide treadmill in the configurations of handle height (100 cm and 110 cm), handle rotation (0 degrees and 90 degrees ), pole angle (0 degrees and 10 degrees ), wheel diameter (8 cm and 15 cm), load weight (15 kg or 23 kg), center of mass (low and middle), carpeting (no and yes), trial day (first and second) and subject height (short and tall). ANOVA revealed that wheel diameter, center of mass and subject height were highly associated with the physical stresses of luggage users, especially their right arm. Although the task seems light work, users should place heavy belongings at the bottom of luggage when packing and manufacturers should give a priority to large wheels for ergonomic design.

Management commitment to safety as organizational support: relationships with non-safety outcomes in wood manufacturing employees.

INTRODUCTION: Employee perceptions of management commitment to safety are known to influence important safety-related outcomes. However, little work has been conducted to explore non-safety-related outcomes resulting from a commitment to safety. METHOD: Employee-level outcomes critical to the effective functioning of an organization, including attitudes such as job satisfaction and commitment to the organization, were included on surveys given to 641 hourly production employees at three wood products manufacturing facilities. Participants' were asked about perceptions of management commitment to safety and job-related variables such as perceived dangerousness of their position, organizational commitment, and withdrawal behaviors. Supervisors also rated the performance of each of their hourly subordinates. RESULTS: Results suggest that employee outcomes differ based on perceptions of management's commitment to safety. Specifically, management commitment to safety was positively related to job satisfaction, organizational commitment, and job-related performance. We also found a negative relationship between commitment to safety and employee withdrawal behaviors. CONCLUSIONS: Our results suggest that increasing employee perceptions of management's personal concern for employee well-being through a dedication to safety will result in positive outcomes beyond improved safety performance. These results also imply that there is a type of social exchange between employees and management that may affect employees similarly to perceived organizational support. IMPACT ON INDUSTRY: Results further reinforce the value of a commitment to safety by a firm's management. Organizations with a strong commitment to safety may enjoy not only a reduction in safety-related events but also increases in desirable employee attitudes and behaviors.