An analysis of scanning postures among grocery cashiers and its relationship to checkstand design

Mounting evidence suggests that musculoskeletal disorders are prevalent among US retail food workers. Cashiers who use electronic scanners appear to be at especially high risk for upper extremity musculoskeletal disorders. Checkstand design has been implicated as a contributor to musculoskeletal injury among cashiers because workstation design can significantly impact working posture. The present study examines working posture among two groups of cashiers to determine if checkstand design is associated with substantial differences in posture and movement during scanning. The work activities of twenty grocery cashiers using one of two checkstand designs (front-facing and right-hand takeaway) were examined. Videotapes of cashiers performing scanning tasks were observed and associated postures and movements were visually coded. The right-hand takeaway design was associated with a significantly higher percentage of non-neutral trunk postures than the front-facing design. However, there were no significant differences in shoulder posture, grasp, or scanning motion associated with checkstand/scanner design. Factors that appeared to affect cashier work posture during scanning included stature, order size, and product type. Although improving the checkstand design may reduce the occurrence of certain awkward postures and static muscle loading conditions among cashiers, the success of these interventions is likely to be limited unless follow-up programmes are instituted to ensure that cashiers are able to use these designs effectively. Furthermore, fundamental changes in cashier work may be required to fully eliminate hazards for musculoskeletal disorders from this job.     

Observed differences in upper extremity forces, muscle efforts, postures, velocities and accelerations across computer activities in a field study of office workers

This study, a part of the PRedicting Occupational biomechanics in OFfice workers (PROOF) study, investigated whether there are differences in field-measured forces, muscle efforts, postures, velocities and accelerations across computer activities. These parameters were measured continuously for 120 office workers performing their own work for two hours each. There were differences in nearly all forces, muscle efforts, postures, velocities and accelerations across keyboard, mouse and idle activities. Keyboard activities showed a 50% increase in the median right trapezius muscle effort when compared to mouse activities. Median shoulder rotation changed from 25 degrees internal rotation during keyboard use to 15 degrees external rotation during mouse use. Only keyboard use was associated with median ulnar deviations greater than 5 degrees. Idle activities led to the greatest variability observed in all muscle efforts and postures measured. In future studies, measurements of computer activities could be used to provide information on the physical exposures experienced during computer use. Practitioner Summary: Computer users may develop musculoskeletal disorders due to their force, muscle effort, posture and wrist velocity and acceleration exposures during computer use. We report that many physical exposures are different across computer activities. This information may be used to estimate physical exposures based on patterns of computer activities over time.     

Characterization of a laboratory model of computer mouse use - applications for studying risk factors for musculoskeletal disorders

In the present study, we assessed the wrist kinetics (range of motion, mean position, velocity and mean power frequency in radial/ulnar deviation, flexion/extension, and pronation/supination) associated with performing a mouse-operated computerized task involving painting rectangles on a computer screen. Furthermore, we evaluated the effects of the painting task on subjective perception of fatigue and wrist position sense. The results showed that the painting task required constrained wrist movements, and repetitive movements of about the same magnitude as those performed in mouse-operated design tasks. In addition, the painting task induced a perception of muscle fatigue in the upper extremity (Borg CR-scale: 3.5, p<0.001) and caused a reduction in the position sense accuracy of the wrist (error before: 4.6 degrees , error after: 5.6 degrees , p<0.05). This standardized painting task appears suitable for studying relevant risk factors, and therefore it offers a potential for investigating the pathophysiological mechanisms behind musculoskeletal disorders related to computer mouse use.     

A study on how usability flaws in GUI design increase mouse movements and consequently may affect users' health

The objective of this study is to discuss how software usability flaws may cause a significant increase in mouse movements and, as a potential side effect, may even affect users' health. During the literature review, this article examines the potential relationship between mouse movement and musculoskeletal disorders of the upper extremity, based on studies from medical sciences. Subsequently, in the main part of the present study, three software products were selected that had at least one usability flaw related to extra mouse movement (the selection of the software was made out of over 20 software programs that had been evaluated in our Software Quality Assessment Laboratory). For these products, all additional mouse movements were measured, involving actual users in various settings and computer configurations. The findings showed that even a single usability flaw may increase mouse movement to a magnitude of between 3.6 and 4.7 m/h. The article concludes that the role of software engineering is to focus on software usability as well, taking into account that a user friendly graphical user interface (GUI) which is able to eliminate unnecessary mouse movement may also eventually contribute to the reduction of fatigue and discomfort, caused by musculoskeletal disorders.     

Validity of the modified RULA for computer workers and reliability of one observation compared to six

Awkward body posture while typing is associated with musculoskeletal disorders (MSDs). Valid rapid assessment of computer workers' body posture is essential for the prevention of MSD among this large population. This study aimed to examine the validity of the modified rapid upper limb assessment (mRULA) which adjusted the rapid upper limb assessment (RULA) for computer workers. Moreover, this study examines whether one observation during a working day is sufficient or more observations are needed. A total of 29 right-handed computer workers were recruited. RULA and mRULA were conducted. The observations were then repeated six times at one-hour intervals. A significant moderate correlation (r = 0.6 and r = 0.7 for mouse and keyboard, respectively) was found between the assessments. No significant differences were found between one observation and six observations per working day. The mRULA was found to be valid for the assessment of computer workers, and one observation was sufficient to assess the work-related risk factor.     

Design and implementation of a participatory ergonomics program for machine sewing tasks

A participatory ergonomics program was designed and implemented to control and reduce workers' compensation costs within an automobile products manufacturing company. Pareto analysis identified a substantial number of musculoskeletal disorders (MSD) associated with manual, machine sewing of canvas automobile accessory products. This case study will discuss the elements of the participatory ergonomics program, describe its implementation, highlight intervention measures, and present program results. Specifically, during the period of 1993 to 1996, the participatory ergonomics program played a significant part in reducing the number of MSD claims by approximately 85%, and contributed to an overall reduction in workers' compensation incurred loss costs by approximately 42%.     

Prevalence of work-related musculoskeletal and non-musculoskeletal injuries in health care workers: the implications for work disability management

To compare the prevalence of musculoskeletal and non-musculoskeletal injuries in a cohort of workers in Manitoba health care sector, who made injury claims between 2002 and 2012. A retrospective study, using secondary data from WCB Manitoba. Logistic regression was used to determine odds ratios for nature of work-related injuries among different groups of workers. Idiopathic work-related musculoskeletal disorders (WMSD) constituted 74.6% of all the injury claims. Injury risks varied between worker groups, and a significant difference was found within the female group, χ² = 13.4, p = 0.0094, but not among the males. Compared to the married, single workers were more likely to experience traumatic than idiopathic injuries (OR = 1.72, CI, 1.28, 2.29), and much higher risk of traumatic injuries than non-WMSD (OR = 1.93, CI, 1.31, 2.84). Work-related injury risks vary significantly across occupations and worker groups, with idiopathic injuries being higher in high physical tasks.

Practitioner Summary: To compare musculoskeletal and non-musculoskeletal injuries among workers in health care sector, and explore the implications for work disability management. Retrospective study, using workers’ compensation claims data. The risk of idiopathic work-related musculoskeletal disorders continue to be high compared to traumatic and non-musculoskeletal disorders, particularly in tasks that involved high physical activities.     

Children,computer exposure and musculoskeletal outcomes: the development of pathway models for school and home computer-related musculoskeletal outcomes

Children's computer use is rapidly growing, together with reports of related musculoskeletal outcomes. Models and theories of adult-related risk factors demonstrate multivariate risk factors associated with computer use. Children's use of computers is different from adult's computer use at work. This study developed and tested a child-specific model demonstrating multivariate relationships between musculoskeletal outcomes, computer exposure and child factors. Using pathway modelling, factors such as gender, age, television exposure, computer anxiety, sustained attention (flow), socio-economic status and somatic complaints (headache and stomach pain) were found to have effects on children's reports of musculoskeletal symptoms. The potential for children's computer exposure to follow a dose–response relationship was also evident. Developing a child-related model can assist in understanding risk factors for children's computer use and support the development of recommendations to encourage children to use this valuable resource in educational, recreational and communication environments in a safe and productive manner.

Practitioner Summary: Computer use is an important part of children's school and home life. Application of this developed model, that encapsulates related risk factors, enables practitioners, researchers, teachers and parents to develop strategies that assist young people to use information technology for school, home and leisure in a safe and productive manner.     

Left-handed versus right-handed computer mouse use: effect on upper-extremity posture

Alternatives to reduce postural constraints have to be sought in order to reduce musculoskeletal complaints related to computer work. This study aimed at documenting the impact of using the mouse on the left side of a standard keyboard (with a right numeric keypad) on upper-extremity posture. A simulated computer task was performed by 27 subjects in a laboratory before and 1 month after ergonomics training. Shoulder flexion and abduction, as well as wrist extension were reduced with left-handed mouse use. Sixteen of the 27 subjects truly converted to using the mouse with the left hand. After a month of using the mouse with the left hand, the time required to perform the same task reduced, the perceived difficulty and discomfort improved, though the time to perform the task was still longer than when using the mouse with the right hand. For work involving both keyboard and mouse use, and without the need of the numeric keypad, it would probably be preferable to use a keyboard without the numeric keypad if the mouse is to be used on the right-hand side. If such keyboards are unavailable, an interesting alternative would be to use the mouse on the left side provided sufficient time is allowed to get accustomed to it.     

Wrist and forearm postures and motions during typing

Awkward upper extremity postures and repetitive wrist motions have been identified by some studies as risk factors for upper extremity musculoskeletal disorders during keyboard work. However, accurate body postures and joint motions of typists typing on standardized workstations are not known. A laboratory study was conducted to continuously measure wrist and forearm postures and motions of 25 subjects while they typed for 10 – 15 min at a standard computer workstation adjusted to the subjects' anthropometry. Electrogoniometers continuously recorded wrist and forearm angles. Joint angular velocities and accelerations were calculated from the postural data. The results indicate that wrist and forearm postures during typing were sustained at non-neutral angles; mean wrist extension angle was 23.4 ± 10.9 degrees on the left and 19.9 ± 8.6 degrees on the right. Mean ulnar deviation was 14.7 ± 10.1 degrees on the left and 18.6 ± 5.8 degrees on the right. More than 73% of subjects typed with the left or right wrist in greater than 15 degrees extension and more than 20% typed with the left or right wrist in greater than 20 degrees ulnar deviation. Joint angles and motions while typing on an adjusted computer workstation were not predictable based on anthropometry or typing speed and varied widely between subjects. Wrist motions are rapid and are similar in magnitude to wrist motions of industrial workers performing jobs having a high risk for developing cumulative trauma disorders. The magnitude of the dynamic components suggests that wrist joint motions may need to be evaluated as a risk factor for musculoskeletal disorders during typing.     

Wrist and forearm postures and motions during typing.

Awkward upper extremity postures and repetitive wrist motions have been identified by some studies as risk factors for upper extremity musculoskeletal disorders during keyboard work. However, accurate body postures and joint motions of typists typing on standardized workstations are not known. A laboratory study was conducted to continuously measure wrist and forearm postures and motions of 25 subjects while they typed for 10-15 min at a standard computer workstation adjusted to the subjects' anthropometry. Electrogoniometers continuously recorded wrist and forearm angles. Joint angular velocities and accelerations were calculated from the postural data. The results indicate that wrist and forearm postures during typing were sustained at non-neutral angles; mean wrist extension angle was 23.4 +/- 10.9 degrees on the left and 19.9 +/- 8.6 degrees on the right. Mean ulnar deviation was 14.7 +/- 10.1 degrees on the left and 18.6 +/- 5.8 degrees on the right. More than 73% of subjects typed with the left or right wrist in greater than 15 degrees extension and more than 20% typed with the left or right wrist in greater than 20 degrees ulnar deviation. Joint angles and motions while typing on an adjusted computer workstation were not predictable based on anthropometry or typing speed and varied widely between subjects. Wrist motions are rapid and are similar in magnitude to wrist motions of industrial workers performing jobs having a high risk for developing cumulative trauma disorders. The magnitude of the dynamic components suggests that wrist joint motions may need to be evaluated as a risk factor for musculoskeletal disorders during typing.     

The Cochran–Weiss–Shanteau performance index as an indicator of upper limb risk assessment expertise

Ergonomists and many other professionals apply ergonomics principles to musculoskeletal health problems. This study examines whether there are differences when it comes to judgement expertise concerning upper limb disorders (ULDs) between ergonomists and those with less ergonomics training. The Cochran–Weiss–Shanteau (CWS) performance index combines judgement consistency with discrimination into one CWS index. Fifty-eight professionals working in the musculoskeletal health area, from four different professions, judged the likelihood of staff complaining of ULDs in a number of written work scenarios containing ULD risk factors. A student group (n = 148) taking an introductory ergonomics module was used as a reference. The ergonomists scored higher on the CWS index than all of the other groups, performing significantly better than all but the occupational health advisors. Performance improved with increased training level but not with experience. This study suggests that ergonomists are quantifiably different from other ergonomics advisors in their judgement performance in this context. Given the global cost of musculoskeletal disorders, assessing the expertise of those giving ergonomics advice for the management of musculoskeletal health is of great significance. This study presents a method for assessing judgement performance in ULD risk assessment, an important part of musculoskeletal health management.     

The Suitability for the Work‐Related Musculoskeletal Disorders Checklist Assessment in the Semiconductor Industry: A Case Study

Musculoskeletal disorders and symptoms are common among workers in the semiconductor and related industries. Ergonomic‐related checklists are used to identify musculoskeletal disorder risk factors in the workplace. This study explores the suitability of the Occupational Safety and Health Administration (OSHA) musculoskeletal disorders (MSDs) checklist for use in the semiconductor manufacturing industry. Six companies were enrolled in the current study, and 122 subjects, ranging in age from 21 to 54 years old, were evaluated through a questionnaire survey and field observation using the OSHA MSDs checklist. The observers were administered an ergonomics‐based checklist training course with a duration of 36 hours. Experimental results demonstrated that nearly 50% of subjects reported physical discomfort, with shoulder symptoms (38.5%) being the most common complaint. In addition, the aggregated sensitivity, specificity, and positive predictive values for the MSDs checklist in the six companies were 47.3%, 62.4%, and 30.0%, respectively. This study concluded that the OSHA MSDs checklist appeared to contain better estimates for capturing musculoskeletal discomfort and found that the OSHA MSDs checklist provided an easily administered, proactive surveillance instrument to assist in early identification of musculoskeletal discomfort. © 2012 Wiley Periodicals, Inc.     

Hourly trends in workers' compensation claims

Very few studies have investigated the variations in occupational injuries throughout the day. The main objective of this study was to examine hourly trends in reported claims of occupational injuries and illnesses and their associated cost, with special emphasis on low-back disorders (LBDs) and cumulative trauma disorders (CTDs). The data were obtained from the records of a major insurance carrier. The results showed that the number of claims per hour exhibited a Gaussian-like distribution with highest reported numbers occurring between 07:00 and 11:00 h. There was an observed increase in LBD claims during the morning hours when compared to the afternoon. In addition, there was a pronounced increase in the number of CTD claims at 09:00 h indicating a possible carry-over effect from nocturnal and early morning pain commonly experienced in CTD sufferers. More revealing, normalized claims (per number of people working at a given hour) showed a dramatic increase during the evening and early morning hours when compared to normal working hours. For both the overall and LBD claims, the rates during the night and early morning periods were up to three times higher than during the typical day-time working hours. However, this trend was not as pronounced for the CTD claims. Most of the hourly cost trends were similar to those observed for the claims trends. However, cost information may reveal further insights about the severity of injuries, especially for CTDs. The findings of the study indicate that special attention should be paid to activities and work processes performed during night and early morning hours of the day. It should be noted that this study focused on the 'recording' of time of injury which may or may not correspond to the ‘true’ time of occurrence of an injury or a symptom. Further studies are needed to assess the agreement between the recorded and the actual time of occurrence of an incident, and to better understand the underlying reasons behind the variation in the time of injuries.     

Checkout cashier work and counter design – Video movement analysis, musculoskeletal disorders and customer interaction

This study was conducted in order to analyse checkout cashiers’ movements at a checkout counter during interaction with customers and the prevalence of work-related stress and musculoskeletal disorders in checkout cashiers. In one shop, six cashiers were videotaped during the workday, and 50 cashiers from seven shops from the same chain of stores responded a questionnaire. Cashier activities and movements, customer interaction and counter design issues were analysed from the video data. Prevalence of work-related stress and musculoskeletal disorders was obtained from the questionnaire. It was found that 76% of all items were manually turned or angled. With a better adjustment of the scanner and a standardised positioning of the EAN-code, many of these movements could be avoided. Furthermore the prevalence of musculoskeletal disorders was quite high (68% for the neck). The questionnaire results showed that many cashiers experienced stress, giving a high percentage of cashiers in the “dedication under pressure” group. The behaviour of the customers was the major cause of stress. Other sources of stress arose from bad design or function of the computer system or other technical equipment.

Relevance to industry

In this study several problems regarding cashier work were identified and solutions, relevant to counter and package designers, shop managers and cashiers are suggested. Data obtained on cashier movements and prevalence of musculoskeletal disorders are given.     

Analogue evolutionary brain computer interfaces [Application Notes]

The keyboard is a device that, with its many switches, provides us with an interface that is reliable but also very unnatural. The mouse is only slightly less primitive, being an electro-mechanical transducer of musculoskeletal movement. Both have been with us for decades, yet they are unusable for people with severe musculoskeletal disorders and are themselves known causes of work-related upperlimb and back disorders, both hugely widespread problems [1], [2]. It will be a major contribution to computer interface technology one day to be able to replace mouse and keyboard with Brain-Computer Interfaces (BCIs) capable of directly interpreting the desires and intentions of computer users.     

Corporate ergonomics programme at automobiles Peugeot-Sochaux

An ergonomic assessment tool for design procedures, exclusive to Peugeot-Citro?n, called ECM, was developed and applied at the design stage by method technicians in the 1990s. It generates data, which are followed up by the project leader of a new model and ergonomists until two years before each launch. During this time, vehicle design is subject to modification, to adapt to ergonomic demands. Simplified methods (DACORS and METEO) were also developed to assess workstations on the shop floor in trim and final plants. Assessments were used to grade the workstations into four profiles linked to physical and static requirements. Production technicians are responsible for the application of these local methods on the shop floor. The management of these centres aimed to reduce the risks of musculoskeletal disorders by reduced heavy profiles of these stations. New cases of musculoskeletal disorders, surveyed by the company doctor among workers on the assembly lines had decreased since 1996. In 1999, the incidence increased again, despite the pursuit of ergonomic methods. This increase in musculoskeletal disorders was above all linked to a major reorganisation of work conditions, including a reduction in the cycle time on the assembly line, and to a move into a new workshop.     

The influence of desk and display design on posture and muscle activity variability whilst performing information technology tasks

Desk design and computer display height can affect posture and muscle activation during computer use. Amplitudes of postural variables and muscle activity during computer use do not explain the results from epidemiological studies of musculoskeletal discomfort and disorders related to computer use. The purpose of this study was to assess variability of posture and muscle activity during work with two computer display heights and book/paper, in conjunction with a curved desk designed to provide forearm support and a traditional, straight desk.18 male and 18 female participants performed 10-min tasks involving keying, mousing, reading and writing in six desk/display conditions. 3D posture and surface emg were assessed for the final 2 min of each task.The curved desk resulted in greater postural and muscle activity variation, suggesting an advantage of this supportive surface over the straight desk. There was little difference in variability associated with the two display heights. However, greater variability of posture and muscle activity was evident with the book/paper condition. Non-touch typists had greater neck flexion variation.The design of information technology tasks and workstations can influence the short term variation in posture and muscle activity. Variation is influenced independently of mean postures and muscle amplitudes and therefore needs to be considered to adequately assess the risk of musculoskeletal disorders.     

Assessment of gastroesophageal reflux disease,musculoskeletal symptoms and quality of life in dentists

Background and aimGastroesophageal reflux disease (GERD) has been associated with sick leave, decreased work productivity and poor quality of life. Another possible cause for the development of GERD is the relationship with maintaining the posture in flexion of the spine. The aim of this study was: (1) to compare gastro esophageal reflux with musculoskeletal disorders and quality of life of dentists, (2) to evaluate the association between gastro esophageal reflux such as time in the profession, time working while sitting, musculoskeletal disorders and quality of life of dentists.Methods83 dentists (23 males and 60 females; average age 39.3 years old) participated in the study, who were evaluated for their time in the profession, sitting time, musculoskeletal disorders, quality of life (SF-12v2) and the GERD symptoms using the Frequency Scale for Symptoms of GERD (FSSG) questionnaire.ResultsThe results showed that the majority were female (72.3%) and sendentary (74.7%). A difference was found between the level of GERD with musculoskeletal disorders (p < 0.05) and quality of life (p < 0.05). An association was also found between GERD and working time (p < 0.01), sitting working time (p < 0.05), headache (p < 0.01) and quality of life (p < 0, 01).ConclusionThis study showed that there was an association with working time, sitting time, musculoskeletal disorders, quality of life and GERD in dentists.     

Biomechanics and performance when using a standard and a vertical computer mouse

Objective: to compare the biomechanics and performance while using a vertical computer mouse (VM) and a standard mouse (SM). Methods: muscle activation (electromyography), forearm movements (electrogoniometers), performance (Fitts' Law test) and satisfaction (questionnaire) of 16 subjects were evaluated. Results: there were significant differences between the VM and the SM, respectively, on motion (28° vs. 42° pronation, p = 0.001; 5° ulnar vs. 7° radial deviation, p = 0.016) and muscle activity (13% vs. 16% of extensor carpi activity, p = 0.006; 10% vs. 13% extensor digitorum activity, p = 0.001). VM user satisfaction was good (68); however, time to target was longer (4.2 vs. 3.4 s, p < 0.001). Conclusions: using the VM decreased wrist pronation and lowered wrist extensor muscle activity, but additional training and familiarisation time may be required to improve user performance.

Practitioner Summary: Using a vertical mouse can decrease the exposure to biomechanical risk factors for computer mouse use-related musculoskeletal disorders. Using a vertical computer mouse resulted in less wrist pronation and lower wrist extensor muscle activity. But, training and familiarisation are required.