James D. McGlothlin

Occupational risk factors associated with soft tissue disorders of the shoulder: a review of recent investigations in the literature

Cumulative trauma illness currently accounts for over half of all occupational illness in the United States. From 1987 to 1989 there was a 100% increase in the reported number of cases of cumulative trauma illness (Bureau of Labor Statistics 1990). Shoulder region pain ranks second only to low back and neck pain in clinical frequency, and the occurrence of occupational shoulder illness is on the rise. This paper summarizes findings of a subset of recent epidemiologic, laboratory, and field studies conducted in order to identify occupational risk factors for cumulative trauma disorders (CTDs) of the shoulder region. These studies have identified the following risk factors as being associated with particular shoulder pain syndromes: awkward or static postures, heavy work, direct load bearing, repetitive arm movements, working with hands above shoulder height, and lack of rest. The paper begins with a discussion of several shoulder disorders, includes problems in studying cumulative trauma, presents results of recent studies, and concludes with suggested ergonomic controls that could help to reduce the incidence of shoulder disorders, by eliminating or reducing exposure to the associated risk factors.

An Immersive Virtual Reality Mock-Up For Design Review Of Hospital Patient Rooms

Full scale physical mock-ups of specific hospital units such as patient rooms are routinely utilized to serve the multiple purposes of constructors, designers, and owner stakeholders for healthcare facility projects. The shortcoming with this practice is that the mock-up is constructed during the construction phase and is of limited use for making extensive decisions regarding the functionality of the room design. Three-dimensional visualisation tools offer healthcare facility stakeholders the opportunity to comprehend proposed designs more clearly during the planning and design phases, thus enabling the greatest influence on design decision making. While several options exist, based on their experience with a bariatric patient room model, the authors promote the utilization of Virtual Reality mock-ups for design review because of their enhanced capacity for an immersive, interactive experience with the design and for the long-term utility of such models for the balance of the project life cycle.

A conceptual quantitative model for prevention of work-related carpal tunnel syndrome (CTS)

Abstract In this paper the authors present a pathogenic mechanism of carpal tunnel syndrome (CTS) and a heuristic conceptual model to assess the musculoskeletal stress of manual work for the purpose of establishing quantitative guidelines to prevent work-related CTS. The model is based on the concept that the frictional energy of manual work within the wrist initiates local tenosynovitis as and CTS, the value of the product should not exceed a limit derived from the population-based threshold. Reliable, validated techniques should be used for gathering data on the stress factors of manual work for the purpose of establishing quantative guidelines to control and prevent work-related CTS.

A Long-Term Study of the Development of N2O Controls at a Pediatric Dental Facility

A review is given of National Institute for Occupational Safety and Health (NIOSH) efforts to control N2O at a pediatric dental operatory from 1978 to the present. Measurements of N2O concentrations were made on four occasions before and after installation of different controls, using an infrared analyzer. Air velocity and volumetric flow measurements also were taken, Video imaging was done in some cases simultaneously with real-time N2O measurements to correlate work practices with exposure data. An infrared imaging system was used to identify sources of N2O. Critical components of resulting recommendations for control include monitoring of N2O concentrations; use of engineering controls, such as a scavenging mask, an effective dilution ventilation system, and auxiliary exhaust; good work practices; maintenance of the equipment; and worker education. Data presented strongly supports the hypothesis that better implementation of controls leads to reduction of N2O exposures. N2O concentrations were reduced by a factor of 61 from their initial levels. The current NIOSH recommended exposure limit of 25 ppm TWA during the time of N2O administration appears to be achievable.

Advantages of Real-Time Data Acquisition for Exposure Assessment

Abstract A computerized data acquisition system, utilizing real-time instrumentation and a video taping system, can provide the information necessary to identify the sources or activities which most affect worker exposure levels. Integrated workplace samplers, such as pumps with filters or charcoal tubes, may indicate a certain level of exposure. However, due to the complexity of the process or work cycle, an evaluation of activities affecting exposure patterns may be difficult. Such a system, utilizing a computer, real-time instrumentation, and video taping, has been used successfully in three different NIOSH studies. In the first, a study of manual weigh-out and transfer of powders, the data acquisition system identified the scooping operation as the component of the work cycle which most affected the worker dust exposures. Because of the short work cycle, typically 30 seconds or less, filter sampling could not isolate this work element as the major cause of worker dust exposure. In the second study, an...

On the measurement of human strength

Generation of muscle strength is a complex procedure of myofilament activation, nervous feedforward and feedback control, and use of mechanical leverages within the human body. Since strength measurement directly at the muscle is (currently) not feasible, it is usually done at the outside of the body, at the interface with some kind of a dynamometer. This poses various challenges because of difficult mechanical and physiological modelling of the conditions, and because of difficulties in experimental control. To better understand and measure human motor performance, a model of muscle functions and control is discussed, and means for computer-aided position and motion observation are proposed. Experimental variables are classified, and a taxonomy for static (isometric) and several dynamic measurement techniques is described.

Proactive stability control while carrying loads and negotiating an elevated surface

In this study, proactive stability control while handling loads and negotiating an elevated surface was examined. Ten young healthy males completed two gait-mode conditions—level walking and negotiating a raised surface. Load-handling conditions were: no load, empty box (reduced visual information), and loaded box (reduced visual information combined with increased inertial load). The lower limb trajectory in the sagittal plane was not modified as a function of reduced visual information or increased inertial load. The step width decreased while stepping over the surface and carrying the loaded box. The trunk pitch angle was biased backwards for both the empty box and the loaded box. When carrying the empty box and negotiating the surface, the trunk pitch range of motion (ROM) increased which may have been a strategy to increase visual exteroceptive information. As increased net trunk pitch could destabilize the system, concurrent stabilizing strategies—decreased gait velocity and reduced net trunk roll velocity—were observed. To meet the equilibrium goals when carrying the loaded box, the trunk pitch ROM and net pitch velocity were reduced during both level walking and surface accommodation. Trunk roll ROM was reduced when carrying the load and negotiating the surface. This study extends our knowledge regarding whole body coordination strategies during anticipatory locomotor adaptations.

Robot-related fatality involving a U.S. manufacturing plant employee: Case report and recommendations

Abstract Sanderson, L.M., Collins, J.W. and McGlothlin, J.D., 1986. Robot-related fatality involving a U.S. manufacturing plant employee: Case report and recommendations. Journal of Occupational Accidents, 8: 13–23. This article presents the salient characteristics of the first publicly documented robot-related fatality in the United States and summarizes recommendations for both preventing similar accidents and directing future robotic safety research and practice. In July of 1984, a 34-year-old die cast operator with 15 years experience was pinned between the right rear end of a hydraulic robot and a “safety pole”. This operator was one of approximately 66 operators employed by the die cast company and was considered by many to be among the most adept at working with the plants two robots. The major factor contributing to the death of this worker may have been his own behavior; he had been formally trained and instructed not to enter the envelope while the robot was operational. This American fatality has several characteristics in common with reported Japanese robot fatalities. These characteristics include: experience, entering the robot range of motion with power on, overriding existing safety systems, being struck from behind, and being pinned or crushed at a pinch point between the robot and stationary equipment. Recommendations for prevention of such injuries are made according to broad categories pertaining to ergonomics, training, and supervision. Specific recommendations for future robotic safety research and practice include improving information dissemination and consultation, addressing psychological factors of workers interacting with robots, assessing the effectiveness and limitations of safeguarding, establishing uniform and objective criteria for training and possibly certification, and expanding scientific research to include better surveillance and epidemiologic and ergonomic studies.

Ergonomics. The effect of occupational exposure to environmental tobacco smoke on the heart rate variability of bar and restaurant workers.

Changes in heart rate variability (HRV) have been linked with cardiac disease and death. Exposure to particulate matter from various sources such as tobacco smoke has been shown to cause alterations in HRV. This study investigated the effects of occupational exposure to environmental tobacco smoke (ETS) on HRV. Air monitoring was conducted in three bars in which smoking was permitted and one bar where smoking was not permitted. Pre- and post-work shift heart rate monitoring was conducted on volunteer staff from the establishments. Heart rate variability parameters, including SDNN and RMSSD, were calculated, and the differences between pre- and post-shift values were plotted and analyzed with respect to ETS exposure. Post-shift minus pre-shift values of SDNN and RMSSD significantly decreased with exposure to ETS (p < 0.05). Occupational exposure to ETS may decrease heart rate variability.Changes in heart rate variability (HRV) have been linked with cardiac disease and death. Exposure to particulate matter from various sources such as tobacco smoke has been shown to cause alterations in HRV. This study investigated the effects of occupational exposure to environmental tobacco smoke (ETS) on HRV. Air monitoring was conducted in three bars in which smoking was permitted and one bar where smoking was not permitted. Pre- and post-work shift heart rate monitoring was conducted on volunteer staff from the establishments. Heart rate variability parameters, including SDNN and RMSSD, were calculated, and the differences between pre- and post-shift values were plotted and analyzed with respect to ETS exposure. Post-shift minus pre-shift values of SDNN and RMSSD significantly decreased with exposure to ETS (p < 0.05). Occupational exposure to ETS may decrease heart rate variability.

Ergonomics Case Study: Revised NIOSH Lifting Equation Instruction Issues for Students

This case study investigated the effectiveness of formal instruction of the Revised NIOSH Lifting Equation for university students who may use the equation in their future work. Their successes and challenges were examined through a class exercise and two exams, all of which followed the classroom instruction in applying the Lifting Equation. Results showed students (1) had difficulty determining relevant values for task variables from reading a job description, and (2) generally were able to calculate the Recommended Weight Limit (RWL) and Lifting Index (LI) when task variables were such that the associated multipliers were less than or equal to 1. However, when the multiplier was calculated to be greater than 1, students had difficulty interpreting the result. The task variable and multiplier (consistently the greatest challenge) were the asymmetry task variable, A, and the asymmetric multiplier, AM. Results indicate that the layout of the Job Analysis Worksheet for Step 1 may make it easy to make arithmetic errors when calculating multipliers. It is recommended that the worksheet be redesigned to help individuals decrease the probability of making an arithmetic error when calculating the task variables, multipliers, RWL, and LI. It is also recommended that the redesigned worksheet be tested to determine whether fewer arithmetic errors are made and if the worksheet is less confusing for an inexperienced user to use.