Field evaluation of a modified intervention for overhead drilling.

Drilling holes into concrete or metal ceilings is one of the most physically demanding tasks performed in construction. The work is done overhead with rotary impact hammer drills that weigh up to 40 N. The task is associated with pain and musculoskeletal disorders at the wrist, forearm, shoulder, and back. The mechanism of injury is thought to be the high forces and non-neutral shoulder and wrist postures applied during drilling. Previously, we described a field study of a foot lever and inverted drill press intervention devices that received poor usability ratings compared with the usual method for overhead drilling based on problems with mobility and productivity. Using a participatory intervention model, feedback from construction workers (N = 13) was used to develop a new intervention design that incorporated a wheeled tripod base and a unique method of aligning the drilling column to vertical. A different group of construction workers (N = 23) evaluated usability and fatigue of the new device during their regular overhead drilling in comparison with the usual method. Four of 12 usability ratings were significantly better with the intervention device compared with the usual method. Subjective shoulder fatigue was less with the new intervention (1.1 vs. 3.3; scale 0 to 5; p < 0.001). This difference was supported by objective outcome measures; the mean hand forces during drilling were 26 N with the intervention compared with 245 N with the usual method. The percentage of time with the shoulder flexed or abducted to more than 60 degrees was less with the intervention compared with the usual method (21 vs. 40%; p = 0.007). There was significantly less head extension with the intervention compared with the usual method. There were no significant differences in overall productivity between the two methods. This study demonstrates that a new intervention device for overhead drilling has improved usability and subjective fatigue ratings compared with the usual method. These improvements are most likely due to the reduced hand forces, reduced shoulder abduction and flexion, and reduced drilling time.

A new method for overhead drilling.

In the construction sector, overhead drilling into concrete or metal ceilings is a strenuous task associated with shoulder, neck and back musculoskeletal disorders due to the large applied forces and awkward arm postures. Two intervention devices, an inverted drill press and a foot lever design, were developed then compared to the usual method by construction workers performing their normal overhead drilling activities (n = 14). While the intervention devices were rated as less fatiguing than the usual method, their ratings on usability measures were worse than the usual method. The study demonstrates that the intervention devices can reduce fatigue; however, additional modifications are necessary in order to improve usability and productivity. Devices designed to improve workplace safety may need to undergo several rounds of field testing and modification prior to implementation.

Rest break interventions in stoop labor tasks.

Hand cultivation and harvest of agricultural products constitute strenuous physical tasks. Working with labor-management ergonomics committees in agricultural settings, the UC Agricultural Ergonomics Research Center (AERC) tested an experimental rest and recovery protocol for its impact on symptoms and productivity during two types of work tasks. The experimental condition consisted of adding a 5 min rest break to every working hour in which there was no other scheduled break (e.g., lunchtime). This resulted in an additional 20 min of rest per workday. We tested the intervention in two trials: Trial one compared workers (n=66) randomly assigned to an experimental or a control group during the harvest of commercial strawberries. Trial two utilized a cross-over design (n=16 pairs of workers) to compare experimental and control conditions while workers inserted bud grafts into young 18'' high citrus trees. For both trials, workers under the experimental condition reported significantly less severe symptoms than workers under control conditions. The order in which the intervention was given, however, appeared to result in variations in productivity. We conclude that the introduction of frequent, brief rest breaks may improve symptoms for workers engaged in strenuous work tasks.

A multi-method study evaluating computing-related risk factors among college students.

PURPOSE: To characterize undergraduate computer use using different data collection methods, emphasizing computing-related postures, use patterns and upper extremity musculoskeletal symptoms. SUBJECTS AND METHODS: In Spring, 2004, undergraduate students from a single dormitory at a private university agreed to complete a College Computing & Health Survey. For three separate data collection periods each lasting a week, we observed postures during computer once per period and continuously measured computer input device usage. During these three periods, students self-reported computer usage and symptoms 3-5 times daily. RESULTS: Thirty students participated and all completed the study. Eighty-six percent reported ever experiencing symptoms after computer work. There were no time-related trends across data collection periods for posture, symptoms, and computing activities and patterns. Typed work and communicating (when compared with playing games) were usually the predominant computing activities throughout the semester. There was significantly greater self-reported computer use than that directly measured (p<0.05). CONCLUSION: This is the first study that utilized several methods of exposure assessment to describe computing postures, use patterns and upper extremity musculoskeletal symptoms among a college student cohort. Epidemiological studies need to explore time-related changes such as time of day, weekday, and days into the semester to further understand symptoms, posture, and computer use changes.

Measuring the physical demands of work in hospital settings: design and implementation of an ergonomics assessment.

BACKGROUND: Assessing the physical demands of the heterogeneous jobs in hospitals requires appropriate and validated assessment methodologies. METHODS: As part of an integrated assessment, we adapted Rapid Entire Body Assessment (REBA), using it in a work sampling mode facilitated by a hand-held personal digital assistant, expanding it with selected items from the UC Computer Use Checklist, and developed a scoring algorithm for ergonomics risk factors for the upper (UB) and lower body (LB). RESULTS: The inter-rater reliability kappa was 0.54 for UB and 0.66 for LB. The scoring algorithm demonstrated significant variation (ANOVA p<0.05) by occupation in anticipated directions (administrators ranked lowest; support staff ranked highest on both scores). A supplemental self-assessment measure of spinal loading correlated with high strain LB scores (r=0.30; p<0.001). CONCLUSION: We developed and validated a scoring algorithm incorporating a revised REBA schema adding computer use items, appropriate for ergonomics assessment across a range of hospital jobs.

Ergonomic evaluation of ten single-channel pipettes.

UNLABELLED: Repetitive pipetting is a task that is associated with work-related musculoskeletal disorders of the hand and arm. OBJECTIVE: The purpose of this study was to evaluate the usability and ergonomic performance of commercially available pipettes as determined by user ratings and objective measurements. PARTICIPANTS: Participants were laboratory technicians and scientists at the Lawrence Berkeley National Laboratory with experience performing pipetting tasks. METHODS: Twenty-one experienced pipette users completed a standardized pipetting task with 5 manual and 5 electronic pipettes. After using each pipette, the user rated it for attributes of comfort and usability. RESULTS: Although no single pipette was rated significantly better than all of the others for every attribute tested, some significant differences were found between pipettes. The Rainin Pipet-Lite received the highest overall quality score among manual pipettes, while the Thermo Scientific Finnpipette Novus was the top-ranked electronic pipette. Features correlated with greater hand and arm comfort were lower tip ejection force, lower blowout force, and pipette balance in the hand. CONCLUSIONS: The findings, when considered with participant comments, provide insights into desirable pipette features and emphasize the value of user testing and the importance of the interactions between task, workplace layout, and pipette design.

The effect of two alternative arm supports on shoulder and upper back muscle loading during pipetting.

OBJECTIVE: Pipetting involves static upper arm positions with the pipette held away from the body for sustained periods of time, putting increased musculoskeletal load on the shoulder and upper back. This study explores the effect of using two alternative arm supports while pipetting on muscle loading in the shoulder/neck region. PARTICIPANTS: 15 experienced pipette users participated in this study. METHODS: In a repeated-measures design, participants performed simulated pipetting in a laboratory setting under three arm support conditions: (1) a gel pad on the work surface, (2) a freely-moving counter-balanced forearm support, and (3) no support (control). Surface electromyography (EMG) of the anterior deltoid and upper trapezius muscles were recorded, as well as productivity and subjective usability. RESULTS: Both arm support conditions resulted in significantly lower mean muscle activity of the anterior deltoid and upper trapezius muscles (p<0.001) and significantly higher subjective comfort ratings (p<0.001) compared to the control condition. The freely moving forearm support resulted in significantly lower peak muscle activity in the anterior deltoid compared to the control condition (p<0.001). Productivity was not affected by the arm supports. These findings suggest that arm support may be beneficial in reducing muscle loading and improving comfort in the shoulder and upper back during pipetting. Future studies are needed to measure the impact of these arm supports in the workplace.

Overhead drilling: comparing three bases for aligning a drilling jig to vertical.

PROBLEM: Drilling overhead into concrete or metal ceilings is a strenuous task done by construction workers to hang ductwork, piping, and electrical equipment. The task is associated with upper body pain and musculoskeletal disorders. Previously, we described a field usability evaluation of a foot lever and inverted drill press intervention devices that were compared to the usual method for overhead drilling. Both interventions were rated as inferior to the usual method based on poor setup time and mobility. METHOD: Three new interventions, which differed on the design used for aligning the drilling column to vertical, were compared to the usual method for overhead drilling by commercial construction workers (n=16). RESULTS: The usual method was associated with the highest levels of regional body fatigue and the poorest usability ratings when compared to the three interventions. CONCLUSION: Overall, the 'Collar Base' intervention design received the best usability ratings. IMPACT ON INDUSTRY: Intervention designs developed for overhead drilling may reduce shoulder fatigue and prevent subsequent musculoskeletal disorders. These designs may also be useful for other overhead work such as lifting and supporting materials (e.g., piping, ducts) that are installed near the ceiling. Workplace health and safety interventions may require multiple rounds of field-testing prior to achieving acceptable usability ratings by the end users.

Development of a method for evaluating accessibility of medical equipment for patients with disabilities.

OBJECTIVE: The purpose of this study was to develop a method for evaluating accessibility of medical equipment for patients with disabilities. METHODS: The researchers reviewed videotapes of patient-participants with various physical and sensory disabilities using different types of medical equipment. For each of 11 videotapes, four observers independently identified and documented access and safety barriers, such as physical, sensory, cognitive, and environmental barriers. Inter-observer variability for identifying barrier presence was assessed with kappa statistics for pairs of observers. RESULTS: A list of 10 access and safety barriers was developed through an iterative consensus process, which identified design features of medical equipment that presented difficulties for participants with disabilities. The list is useful for identifying and categorizing accessibility problems found in equipment. While reliability of barrier identification was substantial or moderate for some barriers, reconciliation of barrier events identified by multiple video observers is recommended for optimal results.

Self-reported pain and physical signs for musculoskeletal disorders in the upper body region among Los Angeles garment workers.

Reports of pain and physical exam findings for musculoskeletal disorders (MSDs) are two common outcome measures independently used to assess work-related MSDs in the scientific literature. How these measures correlate with each other, however, is largely unknown. We recruited 520 sewing machine operators to describe the correlation between subjective self-reported pain and physical findings of MSDs in three upper body regions including the neck/shoulder, elbow/forearm, and hand/wrist. Self-reports of pain and physical findings resulted in different and partly non-overlapping classifications of subjects as MSD cases in our study. Both outcome measures were found to be consistently associated with 'having a medical history of MSDs', 'perceived physical exertion', 'perceived job insecurity' (neck/shoulder), being of older age (arm/forearm), and female gender (arm/forearm and hand/wrist); however, we observed inconsistency for the measures for a number of other job related factors such as 'operating a single machine' and 'number of work hours per week'. Because to date no agreed upon "gold standard" for diagnosing MSDs exists, our findings suggest that research results can be very different when using self-reported measures versus physical exam findings. Also, in order to evaluate the success of an intervention, screening, or surveillance program for work related MSDs, it is important to define clearly which outcome measure best to employ.

Evaluation of two posture survey instruments for assessing computing postures among college students.

OBJECTIVE: To determine agreement between two posture assessment survey instruments and which, if any, were correlated with experiencing upper extremity musculoskeletal symptoms. METHODS: Thirty undergraduate participants had three postural assessment surveys completed, one each for three separate 7-day data collection periods during a semester. Two observation assessment tools were used, a modified Rapid Upper Limb Assessment (mRULA) for computer users for the right and left limbs and the University of California Computer Use Checklist. Concurrently, upper extremity musculoskeletal symptom experience paired to each postural assessment was measured. Lin's concordance correlation coefficient evaluated survey agreement and multi-level statistical models described associations between survey responses and symptoms. RESULTS: There was no agreement between the two postural assessment tool scores (p> 0.85). In adjusted models, the UC Computer Use Checklist was positively associated with symptoms occurrence (OR=1.4, 90% CI 1.2-1.6 for any symptoms; OR=1.3, 90% CI 1.0-1.6 for moderate or greater symptoms). Associations with mRULA scores were inconsistent in that they were sometimes protective and sometimes indicators of risk, depending on the covariates included in the models. CONCLUSION: The mRULA for computer users and the UC Computer Use Checklist were independent of each other; however, due to the inconsistent associations with symptoms we cannot conclude one instrument is superior to the other. Our data do suggest the UC Computer Use Checklist demonstrates a traditional relationship with symptoms, where increasing scores signifiy greater risk. We observed a nontraditional relatioship with symptoms for the mRULA for computer users that needs to be further examined. This is a pilot study and, thus, findings should be interpreted as exploratory. Associations observed in the current study will be used to test hypotheses in the cohort study recently conducted.

A randomized controlled trial of chair interventions on back and hip pain among sewing machine operators: the los angeles garment study.

OBJECTIVE: Determine whether an adjustable chair with a curved or a flat seat pan improved monthly back and hip pain scores in sewing machine operators. METHODS: This 4-month intervention study randomized 293 sewing machine operators with back and hip pain. The participants in the control group received a placebo intervention, and participants in the intervention groups received the placebo intervention and one of the two intervention chairs. RESULTS: Compared with the control group, mean pain improvement for the flat chair intervention was 0.43 points (95% CI = 0.34, 0.51) per month, and mean pain improvement for the curved chair intervention was 0.25 points (95% CI = 0.16, 0.34) per month. CONCLUSIONS: A height-adjustable task chair with a swivel function can reduce back and hip pain in sewing machine operators. The findings may be relevant to workers who perform visual- and hand-intensive manufacturing jobs.

A randomized controlled trial evaluating the effects of new task chairs on shoulder and neck pain among sewing machine operators: the Los Angeles garment study.

STUDY DESIGN: This is a 4-month randomized controlled trial to evaluate the effect of chair design on neck/shoulder pain among sewing machine operators. OBJECTIVE: Determine whether a chair with a curved seat pan leads to improved changes in monthly neck/shoulder pain scores compared with a control intervention. SUMMARY OF BACKGROUND DATA: Sewing machine operators experience a high prevalence and severity of neck and shoulder pain in comparison to other working populations probably due to the sustained shoulder abduction and neck and upper back flexion required of the task. An adjustable height task chair that supports a forward sitting posture may reduce these posture-related risk factors and reduce neck/shoulder pain. MATERIALS AND METHODS: A total of 277 sewing machine operators with neck/shoulder pain were assigned to receive 1) miscellaneous items (control group), 2) a chair with a flat seat pan plus miscellaneous items, or 3) a chair with a curved seat pan plus miscellaneous items. Participants completed a monthly questionnaire assessing neck/shoulder pain severity. RESULTS: Based on estimates of pain score changes from a repeat-measures linear regression, participants who received the flat seat chair experienced a decline in pain of 0.14 (95% confidence interval, 0.07-0.22) points per month compared with those in the control group, while those who received the curved seat experienced a decline of 0.34 (95% confidence interval, 0.28-0.41) points per month compared with those in the control group. These estimates did not change after adjustment for potential covariates. CONCLUSIONS: These findings demonstrate that an adjustable height task chair with a curved seat pan can reduce neck and shoulder pain severity among sewing machine operators.

DEVELOPMENT AND EVALUATION OF A NEW DEVICE FOR OVERHEAD DRILLING.

Drilling overhead into concrete is a strenuous task that is associated with shoulder, arm, neck and back musculoskeletal disorders due to the forceful and awkward aspects of the work. This common task is done to hang pipes, ducts and trays and is performed by construction workers in the electrical, pipe fitting, sheet metal, ironwork and carpentry trades. In this project, alternative devices for overhead drilling were developed in order to reduce the high shoulder loads. The design premise for the alternative devices was adopted from interventions developed on construction sites. These devices were evaluated for usability, productivity, and fatigue in two rounds of testing by 30 construction workers performing their usual overhead drilling. After each round of testing the device designs were modified based on feedback. The final design was associated with much less arm fatigue but similar productivity compared to the usual method for overhead drilling. The feedback, design suggestions and field testing by experienced construction workers was vital to the successful development of these devices. Field testing were done with real tasks, in diverse field settings, with subjects familiar with the task. Multiple rounds of field testing and redesign can significantly improve the safety and usability of new tools. Having experienced workers accessing the new tools can help with determining if and how a new tool is compatible and beneficial to current work practices.

The association of socioeconomic status and psychosocial and physical workplace factors with musculoskeletal injury in hospital workers.

BACKGROUND: The combined effect of socioeconomic, organizational, psychosocial, and physical factors on work-related musculoskeletal disorders (WRMSDs) were studied in a heterogeneous, socioeconomically diverse sample (cases and their matched referents) of hospital workers. METHODS: Cases were defined by a new acute or cumulative work-related musculoskeletal injury; referents were matched by job group, shift length, or at random. Information was obtained through telephone interviews and on-site ergonomics observation. Questionnaire items included sociodemographic variables, lost work time, work effectiveness, health status, pain/disability, and psychosocial working conditions using Effort Reward Imbalance (ERI) and Demand-Control (DC) models. Two multivariate models were tested: Model 1 included occupation as a predictor; Model 2 included education-income as a predictor. RESULTS: Cases reported greater pain, disability, lost time, and decreased work effectiveness than the referents. Model 1 was statistically significant for neck/upper extremity injury (Chi-square = 19.3, P = 0.01), back/lower extremity injury (Chi-square = 14.0, P = 0.05), and all injuries combined (Chi-square = 25.4, P = 0.001). "Other Clinical" occupations (34% mental health workers) had the highest risk of injury (OR 4.5: 95%CI, 1.7-12.1) for all injuries. The ERI ratio was a significant predictor for neck and upper extremity (OR 1.5: 95%CI, 1.1-1.9) and all injuries (OR 1.3; 95%CI, 1.04-1.5), per SD change in score. CONCLUSIONS: In this study, the risk of WRMSDs was more strongly influenced by specific psychosocial and physical job-related exposures than by broad socioeconomic factors such as education and income.

Priority risk factors for back injury in agricultural field work: vineyard ergonomics.

With support of a NIOSH Community Partners grant, the authors reviewed data from three cooperating vineyard companies in Napa and Sonoma Counties, finding both high rates of evidence of musculoskeletal disorders (MSDs) and identifying priority MSD hazards for intervention. Data from OSHA 200 injury report logs identified 29 reported MSDs and 435 lost workdays in a working population of 194 in a 30-month period. The majority of these (20) involved backstrain. High risk job tasks were identified, including: employer-identified tasks, analysis of injury reports, and ergonomics risk factor checklist survey of task work. Triangulating across these three data groups resulted in identification of high priority tasks, including: hand harvest work, hand pruning, and weeding using shovels. Priority risk factors for back injury in these jobs were: repetitive lifting of heavy loads, repetitive exertion of force by the trunk and upper extremities, and repetitive or sustained awkward postures of the trunk (including full stoop and twisting with loads).

The psychosocial work environment and musculoskeletal disorders: design of a comprehensive interviewer-administered questionnaire.

BACKGROUND: Psychosocial working conditions are likely to contribute to work-related musculoskeletal disorders (WRMSDs), but a lack of standardized measurement tools reflects both the theoretical and methodological limitations of current research. METHODS: An interdisciplinary team including biomedical, behavioral, and social science researchers used an iterative process to adapt existing instruments for an interviewer-administered questionnaire assessing psychosocial workplace exposure related to musculoskeletal disorders. RESULTS: The resulting questionnaire included measures of psychosocial workplace factors based on two theoretical models (the demand-control-support and the effort-reward imbalance models), supplemented by the additional constructs of "emotional demands," and "experiences of discrimination." Other psychosocial and physical measures selected for questionnaire inclusion address physical workload, sociodemographic and anthropometric characteristics, social relations and life events, health behaviors, and physical and psychological health. CONCLUSION: Using an interdisciplinary approach facilitated the development of a comprehensive questionnaire inclusive of key measures of psychosocial factors that may play a role in the complex mechanisms leading to WRMSDs.