Biomedical subjects

Thomas J Armstrong

Publications and source records attributed to Thomas J Armstrong.

15 recordsLinked to original sources

PubMed2006

Analysis of an observational rating scale for repetition, posture, and force in selected manufacturing settings.

OBJECTIVE: The aim of this work was to quantify the interrater reliability of a set of scales that assess repetition, posture, and force as used on site when examining industrial work. BACKGROUND: Interrater reliability of observational assessment methods can vary depending on the definition of the methods and situations in which they are used. METHOD: In several industries, 846 jobs were assessed using pairs of analysts to rate the repetition, force, and posture of the upper limbs. Twelve analysts with varying experience levels participated. RESULTS: Using an interclass correlation coefficient (ICC), force and repetition had reliability values of .60 and .71 before and .82 and .87 after discussion, respectively. After discussion, peak posture ratings had ICCs of .60 to .83. ICCs for average posture ratings ranged from .31 to .51 initially to .55 to .67 in final ratings. Less experienced analysts changed their initial ratings more than did the senior investigators. CONCLUSION: The high interrater reliability of the repetition and force metrics indicates that a single analyst is appropriate for basic job assessment. Posture ratings benefit greatly from a two-analyst system. Average postures should be assessed across a full range of the scale for interrater reliability assessment. Analyst pairs should be rotated to avoid forming biases. APPLICATION: For basic assessments of forceful exertions and repetitive motions, a single analyst can be used, reducing the resource requirements for both industry and large epidemiological studies.

Humans↗

PubMed2005

Predictors of upper extremity discomfort: a longitudinal study of industrial and clerical workers.

Upper extremity discomfort associated with work activity is common with a prevalence of over 50% in many settings. This study followed a cohort of 501 active workers for an average of 5.4 years. Cases were defined as workers who were asymptomatic or had a low discomfort score of 1 or 2 at baseline testing and went on to report a discomfort score of 4 or above on a 10-point visual analog scale. This change is considered clinically significant. Controls had a low baseline discomfort score and continued to have a low discomfort rating throughout the study. The risk factors found to have the highest predictive value for identifying a person who is likely to develop a significant upper extremity discomfort rating included age over 40, a BMI over 28, a complaint of baseline discomfort, the severity of the baseline discomfort rating and a job that had a high hand activity level (based upon hand repetition and force). The risk profile identified both ergonomic and personal health factors as risks and both factors may be amenable to prevention strategies.

Adult↗

PubMed2005

A longitudinal study of industrial and clerical workers: predictors of upper extremity tendonitis.

Upper extremity tendonitis (UET) associated with work activity is common but the true incidence and risk factors can best be determined by a prospective cohort study. This study followed a cohort of 501 active workers for an average of 5.4 years. Incident cases were defined as workers who were asymptomatic at baseline testing and had no prior history of UET and went on to be diagnosed with an UET during the follow-up period or at the follow-up evaluation. The incident cases were compared to the subset of the cohort who also had no history of an UET and did not develop tendonitis during the study. The cumulative incidence in this cohort was 24.3% or 4.5% annually. The factors found to have the highest predictive value for identifying a person who is likely to develop an UET in the near future included age over 40, a BMI over 30, a complaint at baseline of a shoulder or neck discomfort, a history of CTS and a job with a higher shoulder posture rating. The risk profile identifies both ergonomic and personal health factors as risks and both categories of factors may be amenable to prevention strategies.

Adult↗

PubMed2005

A longitudinal study of industrial and clerical workers: incidence of carpal tunnel syndrome and assessment of risk factors.

This study followed workers over an extended period of time to identify factors which may influence the onset of Carpal Tunnel Syndrome (CTS). The purpose was to evaluate incidence of CTS and to create a predictive model of factors that play a role in the development of CTS. This prospective study followed 432 industrial and clerical workers over 5.4 years. Incident cases were defined as workers who had no prior history of CTS at baseline testing and were diagnosed with CTS during the follow-up period or at the follow-up screening. On the basis of logistic regression, significant predictors for CTS include baseline median-ulnar peak latency difference, a history of wrist/hand/finger tendonitis, a history of numbness, tingling, burning, and/or pain in the hand, and work above the action level of the peak force and hand activity level threshold limit value. This longitudinal study supports findings from previous cross-sectional studies identifying both work related ergonomic stressors and physical factors as independent risk factors for CTS.

Adult↗

PubMed2005

A cross-sectional assessment of the ACGIH TLV for hand activity level.

The ACGIH Worldwide Threshold Limit Value (TLV) for hand activity "considers average hand activity level or "HAL" and peak hand force." We report cross-sectional data that assess the validity of the TLV with respect to symptoms and selected upper extremity musculoskeletal disorders among workers. The prevalence of symptoms and specific disorders were examined among 908 workers from 7 different job sites in relation to the TLV. Worker exposures were categorized as above the TLV, above the TLV Action Limit but below the TLV, or below the TLV Action Limit. Symptoms in the distal upper extremities did not vary by TLV category. Tendonitis in the wrist/hands/fingers did not vary by TLV category, but elbow/forearm tendonitis was significantly associated with TLV category. All measures of carpal tunnel syndrome were associated with TLV category. In all instances, prevalence of symptoms and specific disorders were substantial in jobs that were below the TLV action limit, suggesting that even at "acceptable" levels of hand activity, many workers will still experience symptoms and/or upper extremity musculoskeletal disorders, which may be important in the rehabilitation and return to work of injured workers. Future analyses need to examine the incidence of symptoms and upper extremity musculoskeletal disorders prospectively among workers in relation to the TLV for hand activity.

Adult↗

PubMed2005

Use of a computerized decision support system for primary and secondary prevention of work-related MSD disability.

The present study evaluates the effectiveness of a decision support system used to evaluate and control physical job stresses and prevent re-injury of workers who have experienced or are concerned about work-related musculoskeletal disorders. The software program is a database that stores detailed job information such as standardized work data, videos, and upper-extremity physical stress ratings for over 400 jobs in the plant. Additionally, the database users were able to record comments about the jobs and related control issues. The researchers investigated the utility and effectiveness of the software by analyzing its use over a 20-month period. Of the 197 comments entered by the users, 25% pertained to primary prevention, 75% pertained to secondary prevention, and 94 comments (47.7%) described ergonomic interventions. Use of the software tool improved primary and secondary prevention by improving the quality and efficiency of the ergonomic job analysis process.

Adult↗

PubMed2005

Predictors of persistent elbow tendonitis among auto assembly workers.

INTRODUCTION: Lateral and medial epicondylitis associated with work activity is a common upper extremity musculoskeletal disorder with a prevalence of 4-30% depending upon the work setting and diagnostic criteria. The influence of treatment, ergonomic factors, medical history, psychosocial variables, and aging on the improvement of symptoms has not been well defined. METHODS: This was a prospective cohort study of a cohort of 45 workers with active elbow tendonitis for an average of 13 months. Complete resolution of symptoms was the defined outcome measure. RESULTS: The predictive factors for persistent elbow tendonitis included older age (OR = 1.1, 95% CI: 0.99, 1.33), higher hand repetition level for their job(s) (OR = 2.5, 95% CI: 1.00, 6.25), more deviation from a neutral wrist position during the work activity (OR = 2.0, 95% CI: 0.80, 5.56), and lower perceived decision authority on the job (OR = 0.9, 95% CI: 0.79, 0.98). Other ergonomic, psychosocial, and electrophysiologic measures were not predictive. The models had relatively high sensitivity and specificity. Treatment effects could not be evaluated due to incomplete data available. CONCLUSIONS: Older workers with jobs requiring more repetition and awkward wrist postures, and less decision authority were less likely to have resolution of their elbow tendonitis. IMPLICATIONS: Workers at highest risk for persistent elbow tendonitis should be placed at jobs with lower repetition levels and that use more neutral wrist postures. Effective interventions must address both the ergonomic and psychosocial risk factors in a multifaceted approach to this problem.

Adult↗

PubMed2005

Incidence of carpal tunnel syndrome among automobile assembly workers and assessment of risk factors.

OBJECTIVES: This study defined the incidence rate of carpal tunnel syndrome (CTS) among active assembly workers and evaluated risk factors. METHODS: This study followed 189 automobile assembly workers over 1 year. Incident cases were defined as workers who had no current or prior history of CTS and were subsequently diagnosed with CTS by means of active surveillance during the study. RESULTS: The estimated annual incidence rate ranged from 1% to 10%, depending on the case definition. Significant predictors for CTS include a higher baseline median-ulnar peak latency difference, history of wrist/hand/finger tendonitis, history of diabetes, nonneutral wrist and elbow postures, and a lower self-reported social support. CONCLUSIONS: This is similar to other prospective studies that demonstrate both ergonomic and medical history are independent risk factors for development of CTS.

Automobiles↗

PubMed2005

Risk factors for visiting a medical department because of upper-extremity musculoskeletal disorders.

OBJECTIVES: This study followed 279 auto assembly workers over 1 year to identify which factors influenced whether a worker would visit the plant medical department because of an upper-extremity musculoskeletal problem. METHODS: Incident cases were defined as involving workers who had not gone to the plant medical department in the preceding 6 months and then subsequently visited the medical department with a work-related musculoskeletal disorder that was potentially due to repetitive work activity (acute fractures or lacerations were excluded). RESULTS: There were 45 cases identified during the study period. Based on Cox regression analysis, significant predictors for visiting a medical department included exceeding the threshold limit value for hand activity and peak force, a history of diabetes, a current diagnosis of carpal tunnel syndrome, elbow tendonitis, and age under 40 years. CONCLUSIONS: The results of this study are consistent with those of other prospective studies that showed that both ergonomic and past medical history are risk factors for an upper-extremity musculoskeletal disorder and suggests that there is a healthy worker or survivor effect among older workers.

Automobiles↗

PubMed2005

Occupational relevance of subclavian vein thrombosis in association with thoracic outlet syndrome.

OBJECTIVES: Primary subclavian vein thrombosis ("effort thrombosis") is not generally recognized as a work-related disorder, and more knowledge is required on the particular biomechanical risks. An extensive biomechanical risk analysis was performed for a possible work-related case. CASE REPORT: A hard-working 43-year-old race-course farrier received successful surgical treatment for subclavian vein thrombosis. No congenital abnormalities were apparent. At work, the farrier spent 75% of his time with his back bent (generally at > 70 degrees) with his right shoulder flexed and abducted, a position that thereby increased the pressure on the subclavian vein. High average (and peak) stress ratings for the neck and shoulder postures are accompanied by high levels of force and considerable repetitiveness. CONCLUSIONS: Taken together, these forms of biomechanical overload suggest that the leading cause of the subclavian thrombosis suffered by this farrier could have been occupational. Case-control studies on this neglected topic are needed to investigate possible associations between subclavian vein thrombosis and specific occupational activities.

Adult↗

PubMed2004

Observational assessment of forceful exertion and the perceived force demands of daily activities.

The primary objective of this study was to assess the accuracy and precision with which analysts observe and estimate the force produced as subjects performed exertions on a work simulator. Eight analysts observed 32 subjects and estimated force as a percent of subjects' maximum voluntary contraction (% MVC). Analysts exhibited bias toward the mean, as high force exertions (> 67% MVC) were underestimated (mean: 11.6% MVC) and low force exertions (<34% MVC) were overestimated (mean: 6.7% MVC). Average error for medium force exertions (34-67% MVC) was not statistically different from zero (2.1% MVC). For all force levels, precision of the estimate was very poor (standard deviation range: 16.2-20.7% MVC). Experience of the analyst in performing ergonomic analysis did not affect accuracy. A secondary objective of the study was to conduct a survey in which subjects identified activities of daily living they perceived as equivalent to controlled force levels. A total of 59 different activities ranging from minimal force required to near maximum were listed by at least 5% of the participants. This list may be used to assist health care practitioners and patients convey the force demands required of occupational tasks as well as for evaluating the diminished strength of the patient.

Activities of Daily Living↗

PubMed2004

Verbal estimation of peak exertion intensity.

The objectives of this research were to investigate the accuracy and precision with which trained and untrained participants estimate the magnitude of forceful exertion and to evaluate the mathematical relationship between actual and estimated exertion. Three groups of participants estimated, as a percentage of maximum voluntary contraction (%MVC), the magnitude of submaximal exertion for 12 simulated tasks. In addition to the control group, one group was exposed to one physical benchmark (100% MVC) and another to three benchmarks (25%, 75%, and 100% MVC) prior to force estimation. Error (estimated minus actual) significantly decreased (p < .0001) from 14% MVC to 4% MVC with one benchmark and to -3% MVC with three benchmarks, as compared with the control group. Furthermore, the standard deviation decreased significantly (p < .0001 ) from the control group (16.6% MVC) to the one-benchmark group (13.8% MVC) to the three-benchmark group (11.6% MVC), indicating improved precision. Significant interaction effects were observed, but their impact on main effects was negligible. Also, linear, power, and logarithmic regression models described the relationship between perceived and actual exertion equally well (R2 = .64-.81). Applications of this research include improving the accuracy and precision of field-based psychophysical estimates of forceful exertion for epidemiological research and other field-based analyses.

Adult↗

PubMed2002

Short term and long term effects of enhanced auditory feedback on typing force, EMG, and comfort while typing.

Two studies were conducted to determine the effects of enhanced auditory feedback on typing force, electromyography (EMG) and subjective discomfort. The introduction of enhanced auditory feedback caused a 10-20% reduction in 90th percentile typing force, finger flexor EMG, and finger extensor EMG. Adaptation to the enhanced auditory feedback occurred in <3 min. After 1 week of intermittent enhanced auditory feedback there were no differences in typing force or EMG while subjects were typing with or without the enhanced auditory feedback. The continued use of auditory feedback did not further reduce the levels of typing force or EMG after 1 or 2 weeks of exposure.

Adult↗

PubMed2002

The effects of work pace on within-participant and between-participant keying force, electromyography, and fatigue.

A laboratory study was conducted to determine the effects of work pace on typing force, electromyographic (EMG) activity, and subjective discomfort. We found that as participants typed faster, their typing force and finger flexor and extensor EMG activity increased linearly. There was also an increase in subjective discomfort, with a sharp threshold between participants' self-selected pace and their maximum typing speed. The results suggest that participants self-select a typing pace that maximizes typing speed and minimizes discomfort. The fastest typists did not produce significantly more finger flexor EMG activity but did produce proportionately less finger extensor EMG activity compared with the slower typists. We hypothesize that fast typists may use different muscle recruitment patterns that allow them to be more efficient than slower typists at striking the keys. In addition, faster typists do not experience more discomfort than slow typists. These findings show that the relative pace of typing is more important than actual typing speed with regard to discomfort and muscle activity. These results suggest that typists may benefit from skill training to increase maximum typing speed. Potential applications of this research includes skill training for typist.

Adult↗

PubMedDate not supplied

Evaluation of three methodologies for assessing work activity during computer use.

The overall goal of this study was to evaluate three separate methodologies for gathering work activity information among computer users. These methodologies included worker self-report, work sampling, and activity monitoring. A repeated measures design was employed whereby data were collected simultaneously on each subject (n = 51) across three consecutive workdays. Exposure information gathered included keying time, mouse usage, and time spent performing various work tasks (i.e., writing, proofreading, handling documents). Subjects were recruited to represent a wide range of keyboard activity and mouse usage. The study found that worker self-reports overestimated actual keyboard usage by a factor of approximately 1.5 for workers using the keyboard an average of 4 hours per day to a factor of 4 for workers using the keyboard an average of 30 min per day. On average, there was an approximate twofold difference between worker self-reported keying time and that obtained via activity monitoring and work sampling. This trend was similar with regard to time spent using the computer mouse. Worker self-reported mouse usage was approximately twofold higher than that obtained via activity monitoring or work sampling. Self-reported exposure information not only resulted in different estimates, but showed greater variance compared with the other methodologies. The results of this study suggest that the use of worker self-reported exposure information on keying time and mouse usage may not represent an accurate account of time spent performing these tasks. In the context of epidemiological studies work sampling and/or activity monitoring would be more suitable methodologies for obtaining such information.

Adult↗