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BACKGROUND: Laptop computers are used in various places and situations. The number of laptop users experiencing musculoskeletal disorders (MSDs) has increased drastically due to, in part, inappropriate workstations. OBJECTIVE: To investigate the neck and shoulder postures, and muscle activity relative to perceived pain when using the laptop at a low-height table, sofa, and bed. METHODS: Twenty male participants aged 18-25 years were randomly assigned to perform laptop computer operation at 3 workstations for 10 minutes during which neck and shoulder angles, muscle activity, and pain were recorded by using an Electrogoniometer, Electromyography (EMG), and visual analog scale (VAS), respectively. RESULTS: Neck flexions when working at the sofa (18.6°±12.2°) and bed (17.2°±10.5°) were significantly (p < 0.05) greater than that at the low-height table (7.8°±6.5°). However, shoulder flexion when working at the low-height table (28.2°±13.0°) was significantly (p < 0.05) greater than that at the sofa (13.8°±8.6°) and bed (10.91°±7.8°). Working at the low-height table caused the shoulder flexor muscle activity to be significantly (p < 0.05) higher than working at the sofa and bed. Neck pain was reported during laptop computer use at the sofa and bed, and upper back pain when working at the low-height table. CONCLUSIONS: High neck flexion and pain were found while working at sofa and bed, whereas high muscle activity at shoulder and upper back pain were found while working at the low-height table.

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OBJECTIVE: to determine the effects ofback belt use on trunk muscle performance and the association between those performance outcomes with Work-Related Musculoskeletal Disorders (WMSDs). MATERIAL AND METHOD: All manual lifting workers in one grocery distribution, warehouse center were interviewed about the history of illness, back injury, WMSDs, lifting manner and experience of back belt use. They were assessedfor trunk muscles performance including the flexion (F), the extension (E) and the right and left side bridge (RSB and LSB) endurance test and Exercise Level of Lumbar Stabilization test (ELLS). Pearson s correlation and Spearman's rank correlation statistics were used to determine the association. RESULTS: One hundred and seven males, aged 18 to 42 years participated in the study. Most participants had ELLS at levels 2 (31.1%) and 3 (30.2%). The mean F, E, RSB and LSB endurance times were 62.33, 88.62, 77.17 and 77.33 seconds, respectively. The greatest area of WMSDs was the lower back (53.33%). Significant correlations were found between the ELLS and RSB (r = 0.244, p = 0.012) and between the ELLS and LSB (r = 0.199, p = 0.041). Significant correlations were found between pain scale of backpain and ELLS (r = -0.299, p = 0.016). Significant correlations were found between the number of WMSD areas and trunkflexion endurance (r = -0.263, p = 0.007), right trunk endurance (r,= -0.195, p = 0.044), left trunk endurance (r = -0.325, p = 0.001) and endurance ratio of RSB/LSB (r(s) = 0.224, p = 0.022). Furthermore, most participants (84.1%) had imbalanced endurance of RSB/LSB. Duration andfrequency ofback belt use did not correlate with any trunk muscle performance. This may have been because few participants did not wear belts (10.1%) or wore belts sometimes (26.6%). CONCLUSION: Low correlation was found between back belt use and WMSDs. To prevent back injury, the lifting workers should be trained to balance their trunk muscles endurance, especially right and left trunk muscles and to stabilize their lower back while lifting.

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This paper discusses a computer program, ErgoNBC, which provides suggestions regarding the ergonomic settings of a notebook computer (NBC), workstation components, and selected accessories in order to help computer users to assume an appropriate work posture during the NBC work. From the users' body height, NBC and workstation component data, ErgoNBC computes the recommended tilt angle of NBC base unit, NBC screen angle, distance between the user and NBC, seat height and work surface height. If necessary, the NBC base support, seat cushion and footrest, including their settings, are recommended. An experiment involving twenty-four university students was conducted to evaluate the recommendations provided by ErgoNBC. The Rapid Upper Limb Assessment (RULA) technique was used to analyze their work postures both before and after implementing the Ergo NBC's recommendations. The results clearly showed that ErgoNBC could significantly help to improve the subjects' work postures.

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OBJECTIVE: The present study evaluated the changes in trunk-stabilizer electromyography (EMG) activities during manual lifting with and without a back belt in experienced back belt users. MATERIAL AND METHOD: Eighteen participants from a warehouse and distribution center in Thailand, aged 22 to 44 years, were assessed for trunk stabilizer muscle EMG activity including the rectus abdominis (RA), external abdominal oblique (EO), transversus abdominis (TrA), internal abdominal oblique (IO), erector spinae (ES), and multifidus (MF). The EMG data were recorded during (1) rest and (2) the initial phase of manual lifting in a dynamic semi-squat posture. For both conditions, the data were compared with and without wearing a back belt. RESULTS: The results showed that wearing a back belt significantly decreased TrA/IO activity during rest (p<0.01) and significantly increased RA activity during the lifting period (p<0.05) as compared with the condition of no back belt. CONCLUSION: The present study does not recommend healthy workers wear a back belt as a protective device for lower back injury, particularly without any lifting activity. However the back belt can be applied during lifting as it can enhance RA activity, which may help improve abdominal pressure and is less likely cause weakness of the TrA.

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Children are likely to assume very awkward seated postures when using a desktop computer at workstations with limited adjustability. This also includes the workstations that are not built for them such as adult visual display terminal (VDT) workstations. This paper proposes simple step-by-step procedures for estimating necessary adjustments so that children can sit and maintain an appropriate seated posture at VDT workstations with limited adjustability (i.e., fixed keyboard and monitor heights). From the anthropometric and VDT workstation data, the procedures compute the recommended VDT workstation settings for a concerned child, compare them with the actual workstation adjustment ranges, determine the appropriate settings, and suggest necessary accessories. The posture adjustment procedures are tested on four Thai children seated at two different types of adult VDT workstation. A rapid upper limb assessment (RULA) technique is used to evaluate the children's seated postures both before and after the posture adjustment. Applying the procedures, children need their own VDT workstation that should be fully adjustable. In using an adult workstation, adjustment accessories and the correct settings are required.

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This paper presents a heuristic procedure for assigning assembly tasks to workstations where both productivity and ergonomics issues are considered concurrently. The procedure uses Kilbridge and Wester's algorithm to obtain an initial task-workstation assignment solution which minimizes the balance delay of an assembly line. A task reassignment algorithm was applied to improve the initial solution by exchanging assembly tasks, which smooth postural load among workers, between workstations. A composite index of variation was used to measure the effectiveness of the task-workstation assignment solution. On the basis of clothes assembling, it was found that the task-workstation assignment solution with a minimum composite index of variation can be obtained with relatively equal weights in balance delay and postural load.

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This paper presents an analytic procedure to assist safety practitioners in evaluating the audibility of an existing auditory warning system in their workplaces. Two alarm location models are described: (a) a model with an unknown signal sound level, and (b) a model with a known signal sound level. A heuristic algorithm to determine a minimum number of alarm devices and their locations so that the warning signals can be clearly heard by workers is also proposed. The algorithm considers the ambient noise level, noise levels generated by individual machines, locations where workers are likely to be present, and noise levels at worker locations. From the numerical examples and the computation experiment, both the optimization and heuristic approaches yield solutions that satisfy the 15-dBA constraints. The heuristic approach is efficient in solving large alarm location problems due its capability to find near-optimal solutions within reasonable computation time.

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This paper discusses the design and development of worksheets for helping notebook computer (NBC) users to compute NBC and workstation adjustments so as to assume an appropriate seated posture. The worksheets (one for male users, the other for female ones) require the following information: body height, NBC screen size, work surface height, and seat height. The worksheets contain tables for estimating recommended NBC base angle, NBC screen angle, body-NBC distance, work surface height, and seat height. Additionally, they include flow charts to help NBC users to determine necessary adjustment accessories and their settings.

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This paper discusses 2 heuristic job rotation procedures for preventing industrial workers from being excessively exposed to ergonomics and safety hazards in their workplaces. The objective of the procedures is 2-fold: (a) to find a minimum number of workers required for the given set of jobs, and (b) to determine a set of safe worker-job-period assignments such that all workers' exposure to hazard does not exceed the permissible limit. Here, occupational hazards are divided into 2 categories: single- and variable-limit hazards. In the first category, workers are considered to have equal capability to withstand the hazard; in the second category, the limit of hazard exposure varies for different individuals. Numerical examples are presented to demonstrate the procedures.

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Factors which are likely to affect recommended workstation and notebook computer (NBC) adjustments to obtain ergonomic work posture during NBC operation are investigated. They are: (1) body height, (2) NBC size, and (3) workstation height (i.e., seat and work surface heights). Six recommended adjustments which are evaluated include: (1) footrest height, (2) seat support height, (3) NBC base support height, (4) distance between the user's body and NBC (or user-NBC distance), (5) tilt angle of NBC base, and (6) screen angle. It is found that body height has a significant effect on footrest height and user-NBC distance while NBC size has a significant effect on user-NBC distance, tilt angle of NBC base, and screen angle. Workstation height, on the other hand, does not show any effect on the six recommended adjustments. However, the results suggest that there are interactions between body height and NBC size, and between body height and workstation height when evaluating their effects on footrest height, tilt angle of NBC base, and screen angle.

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This paper discusses the application of analytical algorithms to determine necessary adjustments for operating notebook computers (NBCs) and workstations so that NBC users can assume correct work postures during NBC operation. Twenty-two NBC users (eleven males and eleven females) were asked to operate their NBCs according to their normal work practice. Photographs of their work postures were taken and analyzed using the Rapid Upper Limb Assessment (RULA) technique. The algorithms were then employed to determine recommended adjustments for their NBCs and workstations. After implementing the necessary adjustments, the NBC users were then re-seated at their workstations, and photographs of their work postures were re-taken, to perform the posture analysis. The results show that the NBC users' work postures are improved when their NBCs and workstations are adjusted according to the recommendations. The effectiveness of ergonomic intervention is verified both visually and objectively.

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A decision support system for designing effective noise hazard prevention (NHP) strategies is proposed. NHP consists of four modules: (a) database, (b) input, (c) algorithms, and (d) solution. The user can choose among single-, two-, and three-approach solution procedures. Heuristic and genetic algorithms are used to determine appropriate noise controls (NCs). From the given noise condition and NC budget, NHP recommends a minimum-cost NHP strategy that prevents any worker's daily noise exposure from exceeding the permissible level. If the budget is insufficient, NHP is able to search for a feasible noise hazard strategy that requires a minimum NC budget.

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An analytical design procedure to determine optimal noise hazard control strategies for industrial facilities is presented. Its objective is to determine a set of appropriate noise controls to eliminate or reduce noise levels so that workers' daily noise exposure does not exceed a permissible level. From a given noise control budget, engineering controls will be firstly implemented, followed by administrative controls, and then the use of hearing protection devices. Six optimization models are developed and sequentially applied to select appropriate noise controls without exceeding the budget. Numerical examples are presented to demonstrate the application of the proposed design procedure.

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One important factor that leads to the development of musculoskeletal disorders (MSD) and cumulative trauma disorders (CTD) among visual display terminal (VDT) users is their work posture. While operating a VDT, a user's body posture is strongly influenced by the task, VDT workstation settings, and layout of computer accessories. This paper presents an analytic and rule-based decision support tool called EQ-DeX (an ergonomics and quantitative design expert system) that is developed to provide valid and practical recommendations regarding the adjustment of a VDT workstation and the arrangement of computer accessories. The paper explains the structure and components of EQ-DeX, input data, rules, and adjustment and arrangement algorithms. From input information such as gender, age, body height, task, etc., EQ-DeX uses analytic and rule-based algorithms to estimate quantitative settings of a computer table and a chair, as well as locations of computer accessories such as monitor, document holder, keyboard, and mouse. With the input and output screens that are designed using the concept of usability, the interactions between the user and EQ-DeX are convenient. Examples are also presented to demonstrate the recommendations generated by EQ-DeX.

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Three methods of visual display terminal (VDT) workstation adjustment were compared in this study in order to investigate their effects on the operator's seated posture. The first two methods were adjustments made both with and without any suggestion on the correct seated posture. The third method was an adjustment after which the workstation settings were initially set according to the results recommended by the IntelAd computer program. Ten male and 5 female participants were asked to readjust a VDT workstation until their most comfortable seated posture was obtained. When comparing the final seated postures to the ones ergonomically recommended, it was found that the workstation adjustment assisted by the computer program yielded the best result, followed by the adjustment without any suggestion on the seated posture, and then the adjustment with a suggestion on the seated posture. Furthermore, factors such as gender and typing skill level were not found to have any significant influence on the results.