Questionnaire versus direct technical measurements in assessing postures and movements of the head, upper back, arms and hands

Basis for an FCE methodology for patients with work-related upper limb disorders

A reported reduction in work-related functional capacity in Work-related Upper Limb Disorders (WRULD) patients is among the most common problems in WRULD. The extent to which this reduction in functional capacity can be objectified remains unknown. A validated instrument to test functional capacity in this patient group is unavailable. The objective of this study was to design a Functional Capacity Evaluation (FCE) for WRULD patients working with Visual Display Units (VDU) and provide evidence for content validity. A review to epidemiological literature was conducted to identify physical risk factors for VDU-related WRULD. The results indicate that physical risk factors were related to repetition, duration, working in awkward and static positions and forceful movements of the upper extremity and neck. An FCE was designed based on the risk factors identified. Eight tests were selected to cover all risk factors: the overhead lift, overhead work, repetitive reaching, handgrip strength, finger strength, wrist extension strength, fingertip dexterity, and a hand and forearm dexterity test. Content validity of this FCE was established by providing the rationale, specific objectives and operational definitions of the FCE. Further research is needed to establish reliability and other aspects of validity of the WRULD FCE.

Evaluation of muscular activity, local muscular fatigue, and muscular rest patterns among dentists

In a previous study, dentists reported very high scores for perceived physical workload, but only low to moderate scores for the musculoskeletal system. This is difficult to explain when other occupational groups in the dental services are compared, and is the main reason why the present study was performed. To measure muscular activity, a surface electromyography (sEMG) study was done, and included the subjects who reported neck and shoulder complaints in the previous study. A portable sEMG system (MyoGuard) was used to collect a myoelectric signal on-line and analysis of the myoelectric signal in a computer. sEMG was recorded from both trapezius muscles for approximately 4 h during an ordinary working day. Twenty-seven dentists participated in the study. The results show accumulated rest% fairly close to that of female cashiers and supermarket employees and increased average rectified value percent (ARV%) during work that could contribute to the very high workload perceived by dentists.

Gender differences in self-reported physical and psychosocial exposures in jobs with both female and male workers

OBJECTIVE

The aim was to determine whether men and women with the same job are equally exposed to work-related physical and psychosocial risk factors for musculoskeletal complaints.

METHODS

Men (n = 491) and women (n = 342) in 8 jobs with both female and male workers completed a questionnaire on exposure to work-related risk factors. Gender, job title, and potential confounders were included in the final statistical models. Separate analyses were performed for desk workers and assembly workers.

RESULTS

For most risk factors gender differences in exposure were found. Among desk workers exposures were most often higher for women, which was the opposite for assembly workers.

CONCLUSIONS

Although exposure assessment relied on self-report, it seems unlikely that gender differences in reporting behavior completely explained gender differences in exposure. Thus, gender differences in exposure are present within the same job.

Task based exposure assessment in ergonomic epidemiology: a study of upper arm elevation in the jobs of machinists, car mechanics, and house painters

AIMS

To explore the precision of task based estimates of upper arm elevation in three occupational groups, compared to direct measurements of job exposure.

METHODS

Male machinists (n = 26), car mechanics (n = 23), and house painters (n = 23) were studied. Whole day recordings of upper arm elevation were obtained for four consecutive working days, and associated task information was collected in diaries. For each individual, task based estimates of job exposure were calculated by weighting task exposures from a collective database by task proportions according to the diaries. These estimates were validated against directly measured job exposures using linear regression. The performance of the task based approach was expressed through the gain in precision of occupational group mean exposures that could be obtained by adding subjects with task based estimates to a group of subjects with measured job exposures in a "validation" design.

RESULTS

In all three occupations, tasks differed in mean exposure, and task proportions varied between individuals. Task based estimation proved inefficient, with squared correlation coefficients only occasionally exceeding 0.2 for the relation between task based and measured job exposures. Consequently, it was not possible to substantially improve the precision of an estimated group mean by including subjects whose job exposures were based on task information.

CONCLUSIONS

Task based estimates of mechanical job exposure can be very imprecise, and only marginally better than estimates based on occupation. It is recommended that investigators in ergonomic epidemiology consider the prospects of task based exposure assessment carefully before placing resources at obtaining task information. Strategies disregarding tasks may be preferable in many cases.

Validity of self-assessed reports of occurrence and duration of occupational tasks

To obtain quantitative estimates of the physical workload in epidemiological and intervention studies of musculoskeletal disorders, there is a need to extend task based exposure data to job exposure profiles. For this purpose a work task diary was developed and evaluated. This was validated against direct observations of a day's work for twenty-two female office workers and twenty female hospital cleaners. There was a good agreement regarding the occurrence of the main tasks. However, the less time-consuming tasks were under-reported. Moreover, about two thirds of the changes between tasks were not reported. The difficulties of defining tasks that function as occupational entities seems to be a major reason for the lack of agreement. The underestimation of the duration of breaks/pauses was most pronounced for the cleaners. Still, the diary would be useful for the calculation of job exposure, by time-weighting task exposure data, when the tasks and/or their duration vary between days.

Measurements of wrist and forearm positions and movements: effect of, and compensation for, goniometer crosstalk

Flexible biaxial goniometers are extensively used for measuring wrist positions and movements. However, they display an inherent crosstalk error. The aim was to evaluate the effect, of this error, on summary measures used for characterizing manual work. A goniometer and a torsiometer were combined into one device. An algorithm that effectively compensated for crosstalk was developed. Recordings from 25 women, performing five worktasks, were analyzed, both with and without compensation for crosstalk. The errors in the 10th, 50th and 90th percentiles of the flexion/extension distributions were small, on average <1 degrees. The ulnar/radial deviation distributions were weakly dependent on forearm position. The flexion/extension velocity measures were, for the 50th and 90th percentiles, as well as the mean velocity, consistently underestimated by, on average, 3.9%. For ulnar/radial deviation, the velocity errors were less consistent. Mean power frequency, which is a measure of repetitiveness, was insensitive (error <1%) to crosstalk. The forearm supination/pronation angular distributions were wider, and the velocities higher, than for the wrists. Considering wrist/hand exposure in epidemiologic studies, as well as for establishing and surveillance of exposure limits for prevention of work-related upper extremity musculoskeletal disorders, the crosstalk error can, when considering other errors and sources to variation, be disregarded.

Self-assessed and directly measured occupational physical activities--influence of musculoskeletal complaints, age and gender

This study compares questionnaire assessed physical activity with direct technical measurements among cleaners and office workers, stratified regarding age, gender and self-reported neck/shoulder complaints. During two full working days number of steps was recorded by a pedometer, sitting/standing positions by a posimeter and heart rate by a Sport-Tester. In addition the subjects kept a work task diary for 10 days. There were high intra-individual variations in exposure between the days. Subjects with complaints rated their exposure higher than those without, although they in fact showed lower direct measured exposure. This may imply underestimation of exposure-effect relationships. Rate of perceived exertion showed low correlation with heart rate ratio within the two occupational groups, but high, 0.64 when the two groups were combined. Age and complaints explained 31% of the variance for the cleaners.

Psychosocial risk factors for musculoskeletal symptoms among women working in geriatric care

BACKGROUND

Nursing is a stressful, physically demanding occupation and a rush setting for musculoskeletal problems. The aim of this study is to explore the extent of the association between psychosocial work characteristics and musculoskeletal symptoms among women working in geriatric care.

METHODS

The participants were female employees of all geriatric nursing homes and geriatric hospital wards in Iceland having a staff of 10 or more. A total of 1,886 questionnaires were distributed. The response rate was 80%.

RESULTS

Finding the job mentally difficult, mental exhaustion after one's shift, dissatisfaction with supervisors or the flow of information, insufficient influence at work, dissatisfaction with the hierarchy, intense time pressure, lack of solidarity, dissatisfaction with the job, harassment, violence or threats at work; all of the aforementioned gave crude odds ratios (OR) two or above for one or more musculoskeletal symptoms. Mental exhaustion and harassment, violence, and threats were the factors connected with symptoms from all the body regions studied.

CONCLUSIONS

The extent of the association of work-related psychosocial factors and musculoskeletal symptoms among the geriatric female nursing staff is substantial and needs to be taken into account by occupational health services and others involved in preventive work. Am. J. Ind. Med. 44:679-684, 2003.

Wrist movements among females in a repetitive, non-forceful work

Wrist positions and movements were measured and a physical examination was conducted in 12 female operators in an industrial quality-control work. The handled products are of very low weight, thus, the work can be considered as non-forceful. The work was highly repetitive; 0.54Hz for the right wrist/hand and 0.41Hz for the left. The angular velocities were also high; for the right wrist/hand median value was 30 degrees /s and peak value 108 degrees /s, for the left wrist/hand 24 degrees /s and 88 degrees /s, respectively. The frequency of musculoskeletal disorders was high, especially for the right wrist/hand. Although the work was non-forceful and there were minor extreme positions in the wrists, the results are consistent with reported exposure-response relations in other high-risk jobs. Thus, the repetitiveness and the high velocities are the likely causes for the high prevalence of disorders in the wrists/hands among the operators.

A triaxial accelerometer for measuring arm movements

A triaxial accelerometer used as an inclinometer (INC) (Logger Technology, Sweden) needed to be evaluated for field measurements of arm postures and movements. INC consists of one portable data logger and up to four sensors. Each sensor measures the inclination to the vertical line. The sampling frequency is 20 Hz and, the logger can collect data for up to 12 h. The aim of the present study was to compare INC measurements with those from an optoelectronic measuring system- the Mac Reflex system (OPT) (Qualisys AB, Sweden). For all movements with normal to high velocities INC measured the degree of arm elevation with very high precision. At very high velocities and, especially when the direction of the velocity was perpendicular to the vertical line the largest differences between INC and OPT were found. In field studies INC has proved to be very safe and useful in assessment of arm movements. INC was easy to handle and easy to wear for the researcher and the subject, respectively.

Validity of a self-administered questionnaire for assessing physical work loads in a general population

The aim of the study was to evaluate eight questions concerning physical loads, used in public health questionnaires. Working women and men (203) completed a self-administered questionnaire twice, following a test-retest method. The questions were also validated with a structured interview. Response agreement was calculated with Cohen's kappa statistics with quadratic weights (kappa w). Test-retest agreement varied from 0.74 to 0.92, and inter-method agreement from 0.38 to 0.81. The lowest coefficients were for the questions concerning bent/twisted work postures (kappa w 0.38) and repetitive movements (kappa w 0.39). The results did not indicate any substantial influence of gender, type of work or musculoskeletal complaint. The questions concerning general physical activity and sitting work postures, and physical exercise/sports during leisure times, had good validity. The questions concerning bent/twisted work posture and repetitive movements need to be re-designed.

Validity and reliability of triaxial accelerometers for inclinometry in posture analysis

There is a need for objective and quantitative methods for measuring posture and movement, so that, for instance, exposure-response relationships for work-related musculoskeletal disorders can be established. Inclinometry data have been obtained from triaxial accelerometers based on uniaxial solid-state accelerometers used in conjunction with a computer program to perform co-ordinate transformations. The transducer can be mounted in an arbitrary orientation on a body segment, since if two reference positions are recorded, the co-ordinate system of the transducer can be transformed to that of the body segment. The angular error of the system is small (1.3 degrees), the reproducibility is high (0.2 degrees), and the inherent angular noise is small (0.04 degrees) and independent of the orientation of the device. Under quasi-static conditions, the angular velocities can be derived from the inclinometry data. The angular and the angular-velocity errors can be approximated using the relative deviation of the acceleration magnitude from gravitation. For applications involving a high degree of movement, the accelerometer data are still valid, although they cannot be interpreted as inclination. Used in combination with the computer program, the transducer can be used to measure posture and movement under static and quasi-static conditions, which occur in most areas of occupational work. It is shown that spherical co-ordinates can be used to present the inclinometry data.