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Figueroa-Jacinto R, Armstrong TJ, Zhou W. Normal force distribution and posture of a hand pressing on a flat surface. J Biomech 2018; 79:164-172. [PMID: 30205978 PMCID: PMC10963082 DOI: 10.1016/j.jbiomech.2018.08.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 08/01/2018] [Accepted: 08/10/2018] [Indexed: 11/28/2022]
Abstract
Hand strength data are needed to understand and predict hand postures and finger loads while placing the hand on an object or surface. This study aims to analyze the effect of hand posture and surface orientation on hand force while pressing a flat surface. Twelve participants, 6 females and 6 males ages 19-25, performed three exertions (100%, 30% and 10% MVC- Maximum Voluntary Contraction) perpendicular to a plate in 4 angles (-45°, 0°, 45° and 90° with respect to the horizontal plane) at elbow height. Exertions involved pushing in two postures: (1) whole hand and (2) constrained to only using the fingertips. Inter-digit joint angles were recorded to map hand and finger motions and estimate joint moments for each condition. Participants exerted twice the force when pushing with whole hand vs. fingertips. 72-75% of the total force was exerted over the base of the palm, while only 11-13% with the thumb for exertions at 90°, 45° or 0° plate angles. Males maximum force for pushing at 0°, 45° and 90° plates averaged 49% higher than females for the whole hand and 62% for the fingertips (p < 0.01). There was no significant sex difference (p > 0.05) for the -45° plate. Thumb joint loads were generally higher than the other individual fingers (p < 0.05) in all % MVC and accounted for 12% of total force during whole hand exertions. On average, joint moments were 30% higher during fingertip conditions vs. whole hand. Thumb and finger joint moment magnitudes when pushing the plate at 100% MVC indicated that Metacarpophalangeal (MCP) joint moments were higher (p < 0.05) than Distal Interphalangeal joints (DIP) and Proximal Interphalangeal joints (PIP) under whole hand and fingertips conditions.
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Seo NJ, Armstrong TJ. Effect of elliptic handle shape on grasping strategies, grip force distribution, and twisting ability. ERGONOMICS 2011; 54:961-970. [PMID: 21973007 PMCID: PMC8856563 DOI: 10.1080/00140139.2011.606923] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A generic torque model for various handle shapes has been developed and evaluated using experimental data. Twelve subjects performed maximum isometric torques using circular and elliptic cylinders in medium and large sizes (circular: r = 25.4, 38.1 mm; elliptic: semi-major/minor axes = 30.9/19.3, 47.1/27.8 mm) finished with aluminium and rubber, in two opposite directions. Torque, grip force distribution, and finger position were recorded. Maximum torques were 25%, 7%, and 31% greater for the elliptic, large-size, and rubber-finished cylinders than for the circular, medium-size, and aluminium-finished cylinders, respectively. Greater torque for the elliptic cylinders was associated with 58% greater normal force that the subjects could generate for the elliptic than circular cylinders. The model suggests that greater torques for the large-size and rubber cylinders are related to long moment arms and greater frictional coupling at the hand-cylinder interface, respectively. Subjects positioned their hands differently depending on torque direction to maximise their normal force and torque generation. STATEMENT OF RELEVANCE: Desirable handle features for torque generation may be different from those for grip only. Design of handles per advantageous handle features (e.g., shape, size, and surface) may help increase people's torque strength and contribute to increased physical capacity of people.
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Armstrong TJ, Young J, Woolley C, Ashton-Miller J, Kim H. Biomechanical Aspects of Fixed Ladder Climbing: Style, Ladder Tilt and Carrying. ACTA ACUST UNITED AC 2009. [DOI: 10.1177/154193120905301417] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This study aims to understand the effects of climbing style (hands on rungs vs. hands on rails), ladder pitch and bank, and carrying objects on hand and foot forces. An instrumented ladder was constructed to OSHA 1910.27 Fixed Ladder Standards. Hand and foot forces were recorded for six male and six female subjects as they ascended and descended the ladder. Although significant inter and intra subject climbing styles were observed for rung and rail climbing, it is still possible to draw important conclusions about the effects of climbing style, ladder pitch and bank, and carrying objects up and down ladders. Most of the work to ascend and descend the ladder is performed with the lower limbs. The hands must constantly exert force to prevent falling from a vertical ladder. Less hand force was exerted on the rails than on the rungs. Hand placement during rung climbing is constrained by rung spacing, while hand placement during rail climbing is determined by climber preference. It can be shown that required hand force is related to vertical hand placement and body center of mass position. Even though less resultant hand force was exerted during rail climb, the lateral component of hand force was greater for rail climbing than for rung climbing. Lateral hand forces may tend to destabilize the climber from the center of the ladder. Tilting the ladder forward reduces hand forces, which is consistent with the biomechanics of climbing and with previous studies. Tilting the ladder laterally did not significantly affect peak hand and foot forces, but it did affect the observed load/unload cycle time for hand and foot climbing movements.
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Keyserling WM, Sudarsan SP, Martin BJ, Haig AJ, Armstrong TJ. Effects of low back disability status on lower back discomfort during sustained and cyclical trunk flexion. ERGONOMICS 2005; 48:219-233. [PMID: 15764323 DOI: 10.1080/0014013042000327689] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A laboratory study was conducted to determine the effects of back disability status on endurance time and perceived discomfort during trunk flexion. Eighty participants (40 with chronic or recurrent low back pain (CRLBP), 40 pain-free) were tested. The trunk was flexed to 15 degrees, 30 degrees, 45 degrees and 60 degrees under three conditions: 1) continuous static flexion; 2) cyclical flexion with 20% rest; and 3) cyclical flexion with 40% rest. Each condition was performed for up to 600 s or until the participant reached his/her pain tolerance limit. Dependent variables included time to distracting discomfort (TDD), total endurance time (TET) and perceived discomfort. For continuous exertions, CRLBP participants had lower TDD (p < 0.001), lower TET (p < 0.001) and greater discomfort (p < 0.001) compared to pain-free controls. In both groups, TDD and TET decreased and perceived discomfort increased as the flexion angle increased. For intermittent exertions, CRLBP participants reported greater discomfort than pain-free participants (p < 0.001). Increasing rest from 20 to 40% reduced discomfort in CRLBP participants, but produced no consistent benefit in pain-free participants. To accommodate persons with CRLBP, consideration should be given to reducing both the magnitude (angle) and duration of trunk flexion required by their jobs.
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Armstrong TJ, Franzblau A, Haig A, Keyserling WM, Levine S, Streilein K, Ulin S, Werner R. Developing ergonomic solutions for prevention of musculoskeletal disorder disability. Assist Technol 2003; 13:78-87. [PMID: 12530835 DOI: 10.1080/10400435.2001.10132038] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
Numerous models have been proposed to help understand the relationship between personal and work factors that affect participation in work. The authors use a generic version of these models as a framework for identifying gaps between job demands and worker capacities. They describe metrics for assessing factors associated with causing or aggravating musculoskeletal disorders. Two case examples are presented to illustrate the hierarchical assessment of jobs and the evaluation of gaps between job demands and worker capacities. Finally, the authors describe the development of a job database to facilitate future evaluations.
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Kunselman SJ, Armstrong TJ, Britton TB, Forand PE. Implementing randomization procedures in the asthma clinical research network. CONTROLLED CLINICAL TRIALS 2001; 22:181S-95S. [PMID: 11728623 DOI: 10.1016/s0197-2456(01)00162-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Randomization is a required component for the success of most controlled clinical trials. To ensure that the benefits of randomization are realized, well defined and carefully planned procedures must be put in place prior to the start of a trial. This paper presents a detailed account of the registration and randomization procedures implemented for the first four clinical trials of the Asthma Clinical Research Network.
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Salerno DF, Franzblau A, Armstrong TJ, Werner RA, Becker MP. Test-retest reliability of the Upper Extremity Questionnaire among keyboard operators. Am J Ind Med 2001; 40:655-66. [PMID: 11757042 DOI: 10.1002/ajim.10024] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Questionnaires are often used in research among workers although few have been tested in the working population. The Upper Extremity Questionnaire is a self-administered questionnaire designed for epidemiological studies and tested among workers. This study assessed reliability of the instrument. METHODS A two-part assessment was conducted among 138 keyboard operators as part of a large medical survey. Test-retest reliability was analyzed using the kappa statistic, paired t-test, and intraclass correlation coefficient (ICC). Logistic regression models were used to test the effect of demographic and work-related factors on reliability. RESULTS The average respondent was a white woman, age 35 years, with some college education, in permanent employment with tenure of 1.4 years. Overall, reports of symptoms were stable from Round 1 to 2. Most kappa values for symptom reports were between 0.60 and 0.89. Kappa values for right and left hand diagrams were 0.57 and 0.28, respectively. Among psychosocial items, Perceived Stress and Job Dissatisfaction Scales were most reliable (ICC = 0.88); co-worker support was least reliable (ICC = 0.44). CONCLUSION Reliability of items on the Upper Extremity Questionnaire were generally good to excellent. Reports of symptom severity and interference with work were less stable. Demographic and work-related factors were not statistically significant in modeling the variation in reliability. Repeated use of the questionnaire with similar results suggests findings are applicable to a larger working population.
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Forand PE, Kunselman SJ, Drazen JM, Israel E, Pillari A, Armstrong TJ, Britton TB. Genetic analysis in the Asthma Clinical Research Network. CONTROLLED CLINICAL TRIALS 2001; 22:196S-206S. [PMID: 11728624 DOI: 10.1016/s0197-2456(01)00163-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Because there is reason to believe that genetic variants could account for different treatment responses in subjects with asthma, it is important to collect blood for genetic-analysis purposes when conducting clinical trials in asthma. This article describes issues related to maintaining subject confidentiality, tracking and shipping blood samples, quality control procedures at the laboratory performing the genotyping, and necessary data verification checks when implementing the genetic-analysis database for the Asthma Clinical Research Network.
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Werner RA, Gell N, Franzblau A, Armstrong TJ. Prolonged median sensory latency as a predictor of future carpal tunnel syndrome. Muscle Nerve 2001; 24:1462-7. [PMID: 11745947 DOI: 10.1002/mus.1169] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The purpose of the study was to determine whether abnormal median sensory nerve conduction among asymptomatic workers was predictive of future symptoms suggestive of carpal tunnel syndrome (CTS). This was a prospective study involving 77 workers who were identified as asymptomatic cases with electrodiagnostic findings of median mononeuropathy compared to an age- and sex-matched control group. Follow-up was completed an average of 70 months later, and subjects who reported pain, numbness, tingling, or burning in the distribution of the median nerve, based upon a hand diagram, were classified as having CTS symptoms. The follow-up participation rate was 70%. Among subjects with abnormal median sensory latencies, 23% went on to develop symptoms consistent with CTS within the follow-up period, compared with 6% in the control group (P= .010). Age and hand repetition were also risk factors for CTS, but the majority of asymptomatic workers with a median mononeuropathy do not become symptomatic over an extended time.
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Salerno DF, Franzblau A, Werner RA, Chung KC, Schultz JS, Becker MP, Armstrong TJ. Reliability of physical examination of the upper extremity among keyboard operators. Am J Ind Med 2000; 37:423-30. [PMID: 10706754 DOI: 10.1002/(sici)1097-0274(200004)37:4<423::aid-ajim12>3.0.co;2-w] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND Physical examination is a traditional outcome measure in epidemiological research. Its value as a reliable measure depends, in part, on the prevalence of positive findings. The purpose of this paper is to determine the empirical reliability of physical examination and anthropometry in a field study of upper extremity disorders among keyboard operators. METHODS Two experienced examiners independently performed common provocative tests and procedures in physical examinations of the neck and upper extremity among 160 keyboard operators. Two additional examiners conducted anthropometric surveys among 137 workers. Inter-examiner reliability was assessed with observed agreement, kappa statistics, and intra-class correlations (ICC). RESULTS Observed agreement was between 96% and 100% for neck and upper extremity signs, muscle stretch reflexes, and muscle strength, however, with the exception of provocative tests, reliability statistics were unstable. Among the provocative tests, Phalen and Tinel tests had modest agreement after adjusting for chance (kappa range: 0.20-0.43). The carpal compression test had the best reliability (kappa=0.60 and kappa=0.67, left and right side, respectively). The ICCs for anthropometry ranged from 0.36-0.91. CONCLUSIONS Results from the study showed that statistically, except for the carpal compression test, physical examination contributed minimal reliable information. This was attributed mainly to the low prevalence of positive findings, and generally mild nature of upper extremity disorders in this population. The results are the best estimate of what would be found in a field study with experienced examiners. While it may reduce bias, separating physical examination from medical history may contribute to the poor reliability of findings. With a shift toward reliable measures, resources can be allocated to more effective tools, like questionnaires, in epidemiological research of upper extremity disorders among keyboard operators.
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Gerard MJ, Armstrong TJ, Franzblau A, Martin BJ, Rempel DM. The effects of keyswitch stiffness on typing force, finger electromyography, and subjective discomfort. AMERICAN INDUSTRIAL HYGIENE ASSOCIATION JOURNAL 1999; 60:762-9. [PMID: 10635542 DOI: 10.1080/00028899908984499] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The effects of keyswitch stiffness and key action on typing force, electromyography (EMG), and subjective preference were examined. Each subject's own keyboard (with an audible key click and key activation force of 0.72 N) and three keyboards with no key click that were identical in design but had different key activation forces (0.28 N, 0.56 N, and 0.83 N) were used. Subjects (24 female transcriptionists) typed on each keyboard for 15 min while typing force and left hand surface EMG of the finger flexor and extensor muscles were monitored. Subjects then used one of the keyboards at their workstations for 7 workdays and were monitored again. This procedure was repeated for all four keyboards. Typing force and finger flexor and extensor EMG activity were highest for the 0.83 N keyboard. Lowest EMG values were for the 0.28 N and the 0.72 N audible key click keyboards. Baseline (10th percentile) and median (50th percentile) extensor EMG values were significantly higher than flexor EMG values. Peak (90th percentile) EMG values were comparable for flexors and extensors. Mean subjective discomfort was significantly higher for the 0.83 N keyboard at the fingers (36% higher), lower arm (40% higher), and overall (39% higher). Seventeen of 24 subjects preferred the 0.72 N keyboard, 4 the 0.28 N keyboard, and 3 preferred the 0.56 N keyboard. Results suggest that increasing make force causes typing force and EMG to increase but that the ratio of 90th centile typing force to make force decreases as make force increases. Subjective discomfort was significantly higher for the keyboard with 0.83 N make force. Buckling spring keyboards have better feedback characteristics, which may be responsible for a decrease in the amount of typing force and EMG produced.
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Abstract
Nerve conduction studies play an important role in clinical practice and research. Given their widespread use, reliability of tests merits careful attention. We assessed interexaminer and intraexaminer reliability of median and ulnar sensory nerve measures of amplitude, onset latency, and peak latency. In a two-phase cross-sectional study, two examiners tested 158 workers. Reliability was assessed with intraclass correlations (ICC) and kappa statistics. Median nerve measures were more reliable (ICC range, 0.76 to 0.92) than ulnar measures (ICC range, 0.22 to 0.85). Ulnar-onset latencies had the worst reliability. The median-ulnar peak latency difference was a particularly stable measure (ICC range, 0.79 to 0.92). The median-ulnar peak latency difference had high interexaminer reliability (kappa range, 0.71 to 0.79) for normal tests defined by cut points of 0.8 ms and 0.5 ms. Intraexaminer reliability was higher with the 0.8-ms cut point (kappa = 0.90 and kappa = 0.85 for examiners 1 and 2, respectively). Rather than absolute cut points to describe normality, a more rational interpretation of results can be made with ordered categories or continuous measures.
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Latko WA, Armstrong TJ, Franzblau A, Ulin SS, Werner RA, Albers JW. Cross-sectional study of the relationship between repetitive work and the prevalence of upper limb musculoskeletal disorders. Am J Ind Med 1999; 36:248-59. [PMID: 10398933 DOI: 10.1002/(sici)1097-0274(199908)36:2<248::aid-ajim4>3.0.co;2-q] [Citation(s) in RCA: 143] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND This study examined the relationship of repetitive work and other physical stressors to prevalence of upper limb discomfort, tendinitis, and carpal tunnel syndrome. METHODS Three hundred fifty-two workers from three companies participated. Job exposure levels for repetition and other physical stressors were quantified using an observational rating technique. Ergonomic exposures were rated on a 10-point scale, where 0 corresponded to no stress and 10 corresponded to maximum stress. Job selection was based on repetition (three categories: high, medium, and low) to ensure a wide range of exposures. Physical evaluations on all participating workers were performed by medical professionals and included a self-administered questionnaire, physical exam, and limited electrodiagnostic testing. RESULTS Repetitiveness of work was found to be significantly associated with prevalence of reported discomfort in the wrist, hand, or fingers (odds ratio (OR) = 1.17 per unit of repetition; OR = 2.45 for high vs. low repetition), tendinitis in the distal upper extremity (OR = 1.23 per unit of repetition; OR = 3.23 for high vs. low repetition), and symptoms consistent with carpal tunnel syndrome (OR = 1.16 per unit of repetition; OR = 2.32 for high vs. low repetition). An association was also found between repetitiveness of work and carpal tunnel syndrome, indicated by the combination of positive electrodiagnostic results and symptoms consistent with carpal tunnel syndrome (OR = 1. 22 per unit of repetition; OR = 3.11 for high vs. low repetition). CONCLUSIONS These findings indicate that repetitive work is related to upper limb discomfort, tendinitis, and carpal tunnel syndrome in workers. Further research with a wider range of exposures is needed to evaluate the effects of other physical stresses alone and in combination.
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Homan MM, Franzblau A, Werner RA, Albers JW, Armstrong TJ, Bromberg MB. Agreement between symptom surveys, physical examination procedures and electrodiagnostic findings for the carpal tunnel syndrome. Scand J Work Environ Health 1999; 25:115-24. [PMID: 10360466 DOI: 10.5271/sjweh.413] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
OBJECTIVES The goal of this study was to evaluate the concordance between various clinical screening procedures for carpal tunnel syndrome. METHODS The subject population consisted of 824 workers from 6 facilities. The evaluated procedures included bilateral sensory nerve conduction testing, physical examinations, and symptom surveys, including hand diagrams. The agreement between the outcomes of various combinations of these procedures was assessed by determining the kappa coefficient. RESULTS There was relatively poor overlap between the reported symptoms, the physical examination findings, and the electrodiagnostic results consistent with carpal tunnel syndrome. Overall, only 23 out of 449 subjects (5%) with at least 1 positive finding met all 3 criteria (symptoms, physical examination findings, and electrophysiological results consistent with carpal tunnel syndrome) for the dominant hand. The screening procedures showed poor or no agreement with kappa values ranging between 0.00 and 0.18 for all the case definitions evaluated for carpal tunnel syndrome. CONCLUSIONS The poor overlap between the various screening procedures warns against the use of electrodiagnostic findings alone without the symptom presentation being considered. The results of this study also point to a need for the further development and evaluation of methods for detecting carpal tunnel syndrome.
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Strasser PB, Lusk SL, Franzblau A, Armstrong TJ. Perceived psychological stress and upper extremity cumulative trauma disorders. AAOHN JOURNAL : OFFICIAL JOURNAL OF THE AMERICAN ASSOCIATION OF OCCUPATIONAL HEALTH NURSES 1999; 47:22-30. [PMID: 10205372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
Abstract
This report presents data exploring the relationship between perceived psychological stress and several variables implicated in the etiology of upper extremity cumulative trauma disorders (UECTDs). The sample was 354 workers from three different manufacturing companies. The primary job exposure for the subjects was that they were engaged in jobs that involved repetitious movements of the upper extremities, primarily of the hands and arms. Data collection included a detailed health history, a comprehensive physical examination of the upper extremities, limited electrodiagnostic testing, Cohen's Perceived Stress Scale, Karasek's Job Content Questionnaire, demographic information, and a measurement of repetition. Descriptive analyses, analysis of variance, correlational analyses, and multiple linear regression were used to examine the data. Perceived stress, as measured in this study, was only weakly associated with repetition, job dissatisfaction, and subjective complaints related to UECTDs. In addition, factors generally accepted as related to UECTDs (e.g., repetition, female gender, hormonal influences, and existing medical conditions) were not robust predictors of perceived stress. The major limitation is related to the measurement of perceived psychological stress. Like most psychosocial phenomena, perceived stress is a complex construct, one that is difficult to measure and correlate with health outcomes. Further research is necessary to examine what role, if any, perceived stress may have in the etiology of UECTDs.
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Salerno DF, Franzblau A, Werner RA, Bromberg MB, Armstrong TJ, Albers JW. Median and ulnar nerve conduction studies among workers: normative values. Muscle Nerve 1998; 21:999-1005. [PMID: 9655117 DOI: 10.1002/(sici)1097-4598(199808)21:8<999::aid-mus3>3.0.co;2-0] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
To determine normative values for nerve conduction studies among workers, we selected a subset of 326 workers from 955 subjects who participated in medical surveys in the workplace. The reference cohort was composed exclusively of active workers, in contrast to the typical convenience samples. Nerve conduction measures included bilateral median and ulnar sensory amplitude and latency (onset and peak). Workers with upper extremity symptoms, medical conditions that could adversely affect peripheral nerve function, low hand temperature, or highly repetitive jobs were excluded from the "normal" cohort. Linear regression models explained between 21% and 51% of the variance in nerve function, with covariates of age, sex, hand temperature, and anthropometric factors. The most robust models were fitted for sensory amplitudes in the median and ulnar nerves for dominant and nondominant hands. The median-ulnar difference was least sensitive to adjustment, indicating it is the best measure to use if corrections are not made to account for relevant covariates. A key point was that the magnitude of variance increased with age and anthropometric factors. These findings provide strong evidence that to improve diagnostic accuracy, electrodiagnostic testing should control for relevant covariates, particularly age, sex, hand temperature, and anthropometric factors.
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Werner RA, Franzblau A, Albers JW, Armstrong TJ. Median mononeuropathy among active workers: are there differences between symptomatic and asymptomatic workers? Am J Ind Med 1998; 33:374-8. [PMID: 9513644 DOI: 10.1002/(sici)1097-0274(199804)33:4<374::aid-ajim7>3.0.co;2-u] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The objective was to determine whether symptomatic workers with an abnormal sensory nerve conduction study consistent with carpal tunnel syndrome differed, in terms of electrophysiologic measures, psychosocial, demographic, anthropometric, or ergonomic variables, from workers with an asymptomatic median mononeuropathy. This was a cross-sectional study of active workers at six different work sites. Cases were defined as workers with electrodiagnostic findings of a median mononeuropathy in either hand, based on a 0.5-msec prolongation of the median sensory evoked peak latency compared to the ulnar latency. This group was stratified on the basis of symptoms of numbness, tingling, burning or pain in the hand. The two groups were compared in terms of demographic, anthropomorphic, psychosocial, electrophysiologic, and ergonomic risk factors. Active workers from six different sites were tested; five sites involved manufacturing workers, and one site represented clerical workers. One hundred eighty-four active workers with a median mononeuropathy were documented on nerve conduction studies. These workers represented a subset of more than 700 workers screened at six different locations. The main outcome measure was the patient's report of symptoms of pain, numbness, tingling or burning in the hand or fingers that lasted more than 1 week or occurred three or more times at the initial screening. Workers with a median mononeuropathy who complained of hand symptoms were more likely to be female, to have jobs with higher hand repetition levels, to have higher ratings of job security, not to have a history of diabetes, to use more force in their job with more abnormal postures of their wrist and fingers, and to have a trend toward a more prolonged median sensory distal latency. Most logistic regression models explained less than 15% of the variance (pseudo R2). Women with jobs that have higher ergonomic risks and no history of diabetes were more likely to have reported symptoms associated with carpal tunnel syndrome compared to other workers with a documented median mononeuropathy. Psychosocial variables were not particularly discriminatory. None of the models allows enough precision to predict on an individual basis.
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Rempel D, Serina E, Klinenberg E, Martin BJ, Armstrong TJ, Foulke JA, Natarajan S. The effect of keyboard keyswitch make force on applied force and finger flexor muscle activity. ERGONOMICS 1997; 40:800-808. [PMID: 9336104 DOI: 10.1080/001401397187793] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The design of the force-displacement characteristics or 'feel' of keyboard keyswitches has been guided by preference and performance data; there has been very little information on how switch 'feel' alters muscle activity or applied force. This is a laboratory-based repeated measures design experiment to evaluate the effect of computer keyboard keyswitch design on applied finger force and muscle activity during a typing task. Ten experienced typists typed on three keyboards which differed in keyswitch make force (0.34, 0.47 and 1.02 N) while applied fingertip force and finger flexor electromyograms were recorded. The keyboard testing order was randomized and subjects typed on each keyboard for three trials, while data was collected for a minimum of 80 keystrokes per trial. No differences in applied fingertip force or finger flexor EMG were observed during typing on keyboards with switch make force of 0.34 or 0.47 N. However, applied fingertip force increased by approximately 40% (p < 0.05) and EMG activity increased by approximately 20% (p < 0.05) when the keyswitch make force was increased from 0.47 to 1.02 N. These results suggest that, in order to minimize the biomechanical loads to forearm tendons and muscles of keyboard users, keyswitches with a make force of 0.47 N or less should be considered over switches with a make force of 1.02 N.
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Franzblau A, Salerno DF, Armstrong TJ, Werner RA. Test-retest reliability of an upper-extremity discomfort questionnaire in an industrial population. Scand J Work Environ Health 1997; 23:299-307. [PMID: 9322821 DOI: 10.5271/sjweh.223] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
OBJECTIVES Efforts to understand or to monitor upper-extremity musculoskeletal disorders among workers have usually involved the use of questionnaires. The goal of this study was to assess the test-retest reliability of an upper-extremity discomfort questionnaire among industrial workers. METHODS Test-retest agreement among 148 workers was analyzed using the kappa coefficient for categorical outcomes. Values of kappa greater than 0.75 are considered excellent, values between 0.40 and 0.75 are fair to good, and values of less than 0.40 represent poor agreement beyond chance alone. Test-retest results of continuous measures (eg, visual analogue scale responses) were compared with paired t-tests. RESULTS The test-retest reliability of the questionnaire used to elicit demographic information, medical history, exercise participation, and information on musculoskeletal symptoms among industrial workers appears to be good to excellent in most instances. CONCLUSIONS These results suggest that most results of this discomfort questionnaire are reliable and suitable for use in epidemiologic studies. For reassurance of the robustness of these findings, similar studies should be carried out in other worker populations with this, and other, questionnaire instruments.
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Werner RA, Franzblau A, Albers JW, Armstrong TJ. Influence of body mass index and work activity on the prevalence of median mononeuropathy at the wrist. Occup Environ Med 1997; 54:268-71. [PMID: 9166133 PMCID: PMC1128701 DOI: 10.1136/oem.54.4.268] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVE To determine which proposed risk factor, work activity (industrial v clerical), body mass index (BMI), or other demographic factors had the most influence on the prevalence of median mononeuropathy at the wrist, and if there was an interaction between the risk factors. METHODS This was a cross sectional study of active workers at five different worksites; four were industrial sites and one was clerical. 527 workers were recruited--164 clerical and 363 industrial. The presence of a median mononeuropathy in either hand was measured by electrodiagnostic techniques comparing median and ulnar sensory latencies. RESULTS 30% of workers had an abnormality of the median sensory nerve at the wrist (34% of the industrial v 21% of the clerical workers). The adjusted risk for industrial workers was twice that of clerical workers. Obese workers (BMI > 29) were four times more likely to present with a median mononeuropathy than workers who were normal or slender (BMI < 25). There was no significant interaction between BMI and worksite in relation to median mononeuropathy. Increasing age was also related to an increased risk of median mononeuropathy. CONCLUSIONS Obesity, industrial work, and age are independent risk factors that influence the prevalence of median mononeuropathies among active workers.
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Latko WA, Armstrong TJ, Foulke JA, Herrin GD, Rabourn RA, Ulin SS. Development and evaluation of an observational method for assessing repetition in hand tasks. AMERICAN INDUSTRIAL HYGIENE ASSOCIATION JOURNAL 1997; 58:278-85. [PMID: 9115085 DOI: 10.1080/15428119791012793] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Several physical stressors, including repetitive, sustained, and forceful exertions, awkward postures, localized mechanical stress, highly dynamic movements, exposures to low temperatures, and vibration have been linked to increased risk of work-related musculoskeletal disorders. Repetitive exertions have been among the most widely studied of these stressors, but there is no single metric for assessing exposure to repetitive work. A new methodology enables repetitive hand activity to be rated based on observable characteristics of manual work. This method uses a series of 10-cm visual-analog scales with verbal anchors and benchmark examples. Ratings for repetition reflect both the dynamic aspect of hand movements and the amount of recovery or idle hand time. Trained job analysis experts rate the jobs individually and then agree on ratings. For a group of 33 jobs, repetition ratings using this system were compared to measurements of recovery time within the cycle, exertion counts, and cycle time. Amount of recovery time within the job cycle was found to be significantly correlated with the analysis ratings (r2 = 0.58), as were the number of exertions per second (r2 = 0.53). Cycle time was not related to the analyst ratings. Repeated analyses using the new method were performed 1 1/2 to 2 years apart on the same jobs with the same group of raters. Ratings for repetition differed less than 1 point (on the 10-cm scale), on average, among the different sessions. These results indicate that the method is sensitive to exertion level and recovery time, and that the decision criteria and benchmark examples allow for a consistent application of these methods over a period of time. This method of rating repetition can be combined with similar scales for other physical stressors.
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Werner RA, Franzblau A, Albers JW, Buchele H, Armstrong TJ. Use of screening nerve conduction studies for predicting future carpal tunnel syndrome. Occup Environ Med 1997; 54:96-100. [PMID: 9072016 PMCID: PMC1128658 DOI: 10.1136/oem.54.2.96] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVE To determine if an abnormal sensory nerve conduction study consistent with median mononeuropathy in asymptomatic workers was predictive of future complaints of the hand or finger suggestive of carpal tunnel syndrome. METHODS This was a case-control study of over 700 active workers at five different work sites: four sites involved manufacturing workers and one site represented clerical workers. Patients' reports of symptoms of pain, numbness, tingling, or burning in the hand or finger that lasted more than one week or occurred three or more times after the initial screening were investigated. 77 cases were defined as asymptomatic workers with electrodiagnostic findings of median mononeuropathy in either hand based on a comparison of median and ulnar sensory evoked peak latencies. A difference > or = 0.5 ms was defined as abnormal; a normal difference was < or = 0.2 ms. Controls were asymptomatic age, and sex matched workers with normal nerve conduction studies in both hands. Follow up questionnaires were completed 17 (SD 6) months later. RESULTS The follow up participation rate was 72%. Cases had a 12% risk of developing symptoms during the follow up period compared with 10% in the control group, chi 2 = 0.12, P = 0.73. CONCLUSIONS Abnormal median sensory nerve conduction studies in asymptomatic workers were not predictive of future hand or fingers complaints and if used for preplacement screening among active workers this should be done with caution.
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Werner R, Armstrong TJ, Bir C, Aylard MK. Intracarpal canal pressures: the role of finger, hand, wrist and forearm position. Clin Biomech (Bristol, Avon) 1997; 12:44-51. [PMID: 11415671 DOI: 10.1016/s0268-0033(96)00044-7] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/1996] [Accepted: 06/06/1996] [Indexed: 02/07/2023]
Abstract
OBJECTIVE: The study examined the change in intracarpal canal pressure (ICCP) in relationship to finger, hand, wrist and forearm position. DESIGN: The study was an in vivo measurement of ICCP in seven subjects undergoing a standardized set of manoeuvres that systematically varied finger, hand, wrist, and forearm position. BACKGROUND: It has been known that the ICCP increased with extremes of wrist flexion and extension but the change in pressure in response to radial and ulnar deviation as well as hand and forearm position has not been reported. METHODS: The ICCP was measured using a slit catheter technique; each variation of position was repeated three times with continuous monitoring of ICCP, wrist angulation, and metacarpal-phalangeal joint angulation. RESULTS: The study demonstrated that ICCPs were lowest when the wrist is in a neutral position, the hand relaxed with fingers flexed and the forearm in a semi-pronated position. Wrist extension and flexion resulted in the greatest increase in ICCP followed by forearm pronation and supination. Radial and ulnar deviation also increased the pressure but to a lesser extent. CONCLUSIONS: The findings of this study support the concept that the wrist and forearm should be maintained in a neutral position during vocational and avocational activities in an effort to minimize pressure within the carpal tunnel and thereby reduce the risk of developing carpal-tunnel syndrome. RELEVANCE: It is desirable to know how the ICCP changes in response to change in hand, wrist, and forearm position so that work activities are designed to minimize the pressure within the carpal canal and thus maintain the viability of the median nerve within the carpal canal.
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Martin BJ, Armstrong TJ, Foulke JA, Natarajan S, Klinenberg E, Serina E, Rempel D. Keyboard reaction force and finger flexor electromyograms during computer keyboard work. HUMAN FACTORS 1996; 38:654-664. [PMID: 8976628 DOI: 10.1518/001872096778827288] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
This study examines the relationship between forearm EMGs and keyboard reaction forces in 10 people during keyboard tasks performed at a comfortable speed. A linear fit of EMG force data for each person and finger was calculated during static fingertip loading. An average r2 of .71 was observed for forces below 50% of the maximal voluntary contraction (MVC). These regressions were used to characterize EMG data in force units during the typing task. Averaged peak reaction forces measured during typing ranged from 3.33 N (thumb) to 1.84 N (little finger), with an overall average of 2.54 N, which represents about 10% MVC and 5.4 times the key switch make force (0.47 N). Individual peak or mean finger forces obtained from EMG were greater (1.2 to 3.2 times) than force measurements; hence the range of r2 for EMG force was .10 to .46. A closer correspondence between EMG and peak force was obtained using EMG averaged across all fingers. For 5 of the participants the force computed from EMG was within +/-20% of the reaction force. For the other 5 participants forces were overestimated. For 9 participants the difference between EMG estimated force and the reaction force was less than 13% MVC. It is suggested that the difference between EMG and finger force partly results from the amount of muscle load not captured by the measured applied force.
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Gerard MJ, Armstrong TJ, Foulke JA, Martin BJ. Effects of key stiffness on force and the development of fatigue while typing. AMERICAN INDUSTRIAL HYGIENE ASSOCIATION JOURNAL 1996; 57:849-54. [PMID: 8865594 DOI: 10.1080/15428119691014549] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
An experiment was conducted to investigate the effect of key stiffness on the development of fatigue, keyboard reaction forces, and muscle electromyography (EMG) responses. Six subjects typed continuously for 2 hours on each of two keyboards (0.28 N or 0.83 N resistance keys, presented in random order). Keyboard reaction force and root mean square finger flexor and extensor EMG were recorded for 2 minutes at 250 Hz for every 10 minutes subjects typed. After typing for 2 hours subjects were given a 2-hour rest break and then typed on the remaining keyboard for an additional 2 hours Fifty-four percent more peak force, 34% more peak finger flexor EMG, and 2% more peak finger extensor EMG were exerted while using the 0.83 N keyboard. Peak and 90th percentile values showed similar trends and were well correlated for force and finger flexor and extensor EMG. Subjects typed much harder than necessary (4.1 to 7.0 times harder on the 0.28 N keyboard and 2.2 to 3.5 times harder on the 0.83 N keyboard) to activate the keys. Fatigue was observed on the 0.83 N keyboard during 2 hours of continuous typing, but the trends were mild. It appears that the ratio of typing force to flexor EMG may not be a sensitive enough indicator of fatigue for low-force high repetition work.
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Frederick LJ, Armstrong TJ. Effect of friction and load on pinch force in a hand transfer task. ERGONOMICS 1995; 38:2447-2454. [PMID: 8586074 DOI: 10.1080/00140139508925278] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The effect of friction and load on pinch force was studied in a simple hand transfer task using a repeated measures design and ten men. Subjects moved a container between two targets, 450 mm apart, at a slow, self-paced speed. The levels of mass in the container were set at 0.8, 2.5 and 4.2 kg (7.5, 24.5 and 41.5 N respectively). The handle materials were sandpaper and smooth aluminum. Applied pinch force was measured via a strain gauge mounted in a specially-designed handle attached to the container. Dependent variables were peak and 'steady-state' pinch force. The main and interaction effects of load and friction were significant. The friction effect was significant only for the highest load which, on average, elicited peak pinch forces of 16-70% of maximum voluntary force. This suggests that these men were not sensitive to friction effects at the lower loads. Results suggest that the use of tool handle friction enhancements may reduce required pinch forces for objects requiring upwards of 50% or more of maximum pinch strength.
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Werner RA, Bir C, Armstrong TJ. Reverse Phalen's maneuver as an aid in diagnosing carpal tunnel syndrome. Arch Phys Med Rehabil 1994; 75:783-6. [PMID: 8024425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A reverse Phalen's maneuver involves wrist and finger extension held for 1 minute. We showed that this maneuver results in a significantly higher intracarpal canal hydrostatic pressure as compared to a traditional Phalen's or a modified Phalen's maneuver. Additionally, 31 individuals with complaints of carpal tunnel syndrome symptoms and 20 normal controls were evaluated to see what effect the reverse Phalen's maneuver would have on median sensory latency and amplitude. Both groups demonstrated a prolongation of the median sensory revoked response after 1 minute of this maneuver. The control group had a prolongation of 0.05 ms compared to 0.13 ms in the carpal tunnel syndrome group. The difference between the two groups was significant at a p = 0.05 level. This may add to the sensitivity of conventional screening methods.
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Saldaña N, Herrin GD, Armstrong TJ, Franzblau A. A computerized method for assessment of musculoskeletal discomfort in the workforce: a tool for surveillance. ERGONOMICS 1994; 37:1097-12. [PMID: 8026453 DOI: 10.1080/00140139408963721] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
A musculoskeletal discomfort survey was conducted to assess musculoskeletal discomforts among rural mail carriers in two post offices. Perceived musculoskeletal discomfort was collected directly from the workforce by means of a computerized discomfort assessment system (DAS). This investigation aimed at: (1) assessing the rural mail carrier's perception of DAS; and (2) assessing the rural mail carrier's musculoskeletal discomforts resulting from work. Most participants in the study found the computer tool easy to learn and easy to use. The information collected by DAS was used: (1) to determine the number of participating employees who were experiencing some kind of musculoskeletal problem; (2) to determine subtasks associated with discomfort; (3) to determine the body areas most affected by different subtasks; and (4) to investigate the patterns of discomfort that occurred with time.
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Werner RA, Albers JW, Franzblau A, Armstrong TJ. The relationship between body mass index and the diagnosis of carpal tunnel syndrome. Muscle Nerve 1994; 17:632-6. [PMID: 8196706 DOI: 10.1002/mus.880170610] [Citation(s) in RCA: 133] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Increased weight and, more recently, body mass index (BMI), have been suggested as risk factors for carpal tunnel syndrome (CTS). In an effort to determine the relative risk (RR) of obesity in the development of CTS, 949 patients who had an evaluation of the right upper extremity that included motor and sensory conduction studies of the median and ulnar nerves were reviewed. Of these patients, 261 were diagnosed with a median mononeuropathy at the wrist. Those individuals who were classified as obese (BMI > 29) were 2.5 times more likely than slender individuals (BMI < 20) to be diagnosed with CTS. Forty-three percent of obese women and 32% of obese men had the diagnosis of CTS compared to 21% of slender women and 0% of slender men.
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Armstrong TJ, Foulke JA, Martin BJ, Gerson J, Rempel DM. Investigation of applied forces in alphanumeric keyboard work. AMERICAN INDUSTRIAL HYGIENE ASSOCIATION JOURNAL 1994; 55:30-5. [PMID: 8116526 DOI: 10.1080/15428119491019230] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
This paper considers one way that occupational health professionals can assess the force exerted by keyboard users and the possible relationship between that force and the key force-displacement relationship. First, three personal-computer keyboards with the standard QWERTY layouts were tested as described by the American National Standard for Human Factors Engineering of Visual Display workstations (ANSI/HFS 100-1988) to determine the peak forces, 0.47-0.89N; displacements prior to the "breakaway" force that acknowledges key registration, 2.0-2.5 mm; and total key travel, 3.3-4.3 mm. Second, keyboard reaction forces were recorded while 10 subjects typed 4 alphanumeric sentences on the keyboards. It was found that the peak forces corresponding to each keystroke were 2.5 to 3.9 times the required activation forces, indicating that the subjects consistently displaced the keys to their limits. The average of the peak forces for all keystrokes was lowest for the keyboard with the lowest required activation force. It was concluded that keyboard reaction forces can be used as an index of finger forces for keying tasks. Further studies are necessary to evaluate the relationship between keyboard reaction forces, fatigue, and chronic muscle, tendon, and nerve disorders.
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Ulin SS, Armstrong TJ, Snook SH, Keyserling WM. Perceived exertion and discomfort associated with driving screws at various work locations and at different work frequencies. ERGONOMICS 1993; 36:833-846. [PMID: 8339721 DOI: 10.1080/00140139308967946] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Eighteen subjects drove screws with air-powered tools into perforated sheet metal at three vertical and two horizontal work locations using three different work paces (8, 10, and 12 screws/min). Subjects drove screws with a pistol-shaped tool on the vertical orientation at knee, elbow, and shoulder height. They used an in-line tool to drive screws on the horizontal surface. A horizontal beam was placed just below each subject's elbow height and they drove screws into it with the lower arm perpendicular to the torso and with the arms fully extended. Subjects drove screws for 10 min at each work location and frequency combination before they assessed the condition using the Borg ten-point ratio rating scale. Subjects also ranked seven body areas according to discomfort for each work location. A two-factor ANOVA (and comparable non-parametric statistics) showed that both work location and frequency were significant factors in determining the Borg ratings. As work pace increased, so did the Borg ratings of perceived exertion for each work location. For each incremental increase in work pace, the Borg ratings of perceived exertion increased 12% to 25%, depending on the work location. Driving screws at elbow height on the vertical surface and with the lower arm close to the body on the horizontal surface were the work locations with the smallest ratings of perceived exertion. The ratings of perceived exertion for driving screws at elbow height on the vertical surface were 18% to 50% lower than the ratings for driving screws at knee or shoulder height and the ratings of perceived exertion for driving screws with the lower arm close to the body on the horizontal surface were 21% to 24% lower than driving screws with the arms fully extended. No significant difference was found among the discomfort ranks given to the various body parts for the two horizontal work locations. Differences were found among the body part discomfort rankings for the vertical work locations. While driving screws at knee height, the torso was most stressed; the wrist and hand were most stressed while driving screws at elbow height, and the shoulder and upper arm were the body parts that were stressed the most while driving screws at shoulder height.
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Ulin SS, Armstrong TJ, Snook SH, Franzblau A. Effect of tool shape and work location on perceived exertion for work on horizontal surfaces. AMERICAN INDUSTRIAL HYGIENE ASSOCIATION JOURNAL 1993; 54:383-91. [PMID: 8362759 DOI: 10.1080/15298669391354847] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Thirty subjects drove screws into perforated sheet metal mounted on a horizontal surface using three air-powered tools that varied in shape (right-angle, in-line, and pistol-shaped). The four horizontal work locations ranged from 13-88 cm in front of the body and were placed at 25 cm intervals. The vertical placement of the horizontal beam was at midthigh, elbow, and midchest height. Subjects drove 25 screws at each tool/work location combination before rating that condition using the Borg 10-point ratio rating scale. The ratings of perceived exertion increased with increasing horizontal distance from the body. When tool shape was not considered, the perceived exertion was virtually equal for driving screws at midthigh or elbow height. The ratings at midchest height were significantly higher than elbow and midthigh height. When tool shape was taken into account, subjects perceived less exertion driving screws with the pistol-shaped tool at midthigh height. The in-line and right-angle tools had the lowest ratings of perceived exertion for driving screws at elbow and midchest height.
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Armstrong TJ, Buckle P, Fine LJ, Hagberg M, Jonsson B, Kilbom A, Kuorinka IA, Silverstein BA, Sjogaard G, Viikari-Juntura ER. A conceptual model for work-related neck and upper-limb musculoskeletal disorders. Scand J Work Environ Health 1993; 19:73-84. [PMID: 8316782 DOI: 10.5271/sjweh.1494] [Citation(s) in RCA: 314] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
This paper presents a conceptual model for the pathogenesis of work-related musculoskeletal disorders. The model contains sets of cascading exposure, dose, capacity, and response variables, such that response at one level can act as dose at the next. Response to one or more doses can diminish or increase the capacity for responding to successive doses. The model is used as a framework for discussing the development of work-related muscle, tendon, and nerve disorders. It is intended as a beginning, to be modified to explain new findings as they become available. In research, it can help to identify areas needing additional data for the development and expression of work-related musculoskeletal disorders. Researchers can use it to design laboratory and field studies. In practice, it demonstrates the relationship between common exposure factors and different responses. This information can be used to evaluate and design jobs for the prevention of work-related musculoskeletal disorders.
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Ulin SS, Armstrong TJ. A strategy for evaluating occupational risk factors of musculoskeletal disorders. JOURNAL OF OCCUPATIONAL REHABILITATION 1992; 2:35-50. [PMID: 24242867 DOI: 10.1007/bf01078930] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
There is a large and increasing incidence of work-related muscoloskeletal disorders, both upper extremity cumulative trauma disorders and low back pain. Several occupational risk factors have been linked with the development of musculoskeletal disorders. In order to identify the known occupational risk factors associated with a specific job, an analysis procedure is described to help identify ergonomic risk factors in the workplace. Job analysis should be one part of an overall ergonomics control program. Once the ergonomic risk factors have been documented, the ergonomics committee can use that information to begin developing solutions that will decrease or eliminate the identified risk factors. When placing a worker who is returning to the workforce after recovering from an injury, health care professionals can also use the information from the job analysis to assist in matching up task demands with worker capabilities and limitations.
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Abstract
A kinematic model has been developed for simulation and prediction of the prehensile capabilities of the human hand. The kinematic skeleton of the hand is characterized by ideal joints and simple segments. Finger-joint angulation is characterized by yaw (abduction-adduction), pitch (flexion-extension) and roll (axial rotation) angles. The model is based on an algorithm that determines contact between two ellipsoids, which are used to approximate the geometry of the cutaneous surface of the hand segments. The model predicts the hand posture (joint angles) for power grasp of ellipsoidal objects by 'wrapping' the fingers around the object. Algorithms for two grip types are included: (1) a transverse volar grasp, which has the thumb abducted for added power; and (2) a diagonal volar grasp, which has the thumb adducted for an element of precision. Coefficients for estimating anthropometric parameters from hand length and breadth are incorporated in the model. Graphics procedures are included for visual display of the model. In an effort to validate the predictive capabilities of the model, joint angles were measured on six subjects grasping circular cylinders of various diameters and these measured joint angles were compared with angles predicted by the model. Sensitivity of the model to the various input parameters was also determined. On an average, the model predicted joint flexion angles that were 5.3% or 2.8 degrees +/- 12.2 degrees larger than the measured angles. Good agreement was found for the MCP and PIP joints, but results for DIP were more variable because of its dependence on the predictions for the proximal joints.
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Ulin SS, Ways CM, Armstrong TJ, Snook SH. Perceived exertion and discomfort versus work height with a pistol-shaped screwdriver. AMERICAN INDUSTRIAL HYGIENE ASSOCIATION JOURNAL 1990; 51:588-94. [PMID: 2085164 DOI: 10.1080/15298669091370167] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Seven vertical locations were rated after 36 subjects drove 25 No. 6 sheet metal screws into 18-gauge perforated sheet metal (hole size of 0.28 cm) with an air-powered pistol-shaped screwdriver at each location. The seven vertical heights ranged from 38 to 191 cm. Subjects rated each level using three psychophysical scales and were asked to imagine that they were assembly line workers required to drive screws at that work location using that particular tool for 8 hr. The three scales were the Borg 10-point ratio rating scale and two visual analogue scales. All subjects, regardless of anthropometry (5th percentile females to 95th percentile males), preferred driving screws between 114 and 139 cm. At the highest level of 191 cm, the shortest subjects disliked the level twice as much as the taller subjects. The three psychophysical scales were found to be comparable in sensitivity and use, although most subjects preferred the Borg rating scale. Future research and limitations of the current study are discussed.
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Radwin RG, Armstrong TJ, Vanbergeijk E. Vibration exposure for selected power hand tools used in automobile assembly. AMERICAN INDUSTRIAL HYGIENE ASSOCIATION JOURNAL 1990; 51:510-8. [PMID: 2220569 DOI: 10.1080/15298669091370013] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A practical method for assessing vibration exposure for workers operating vibrating hand tools on an automobile assembly line is presented. Vibration exposure is difficult to assess directly using many fast Fourier transform (FFT) spectral analyzers because of long task cycle times. Exposure time cannot be accurately estimated using time standards because of the high variability between operators and work methods. Furthermore, because workers frequently move about and get into inaccessible spaces, it is difficult to record vibration without interfering with the operation. A work sampling method was used for determining vibration exposure time by attaching accelerometers to the tools and suspending a battery-operated digital data logger from the air hose. Vibration acceleration and frequency spectra for each tool were obtained off-line replicating actual working conditions and analyzed together with exposure time data for determining individual worker vibration exposure. Eight pneumatic vibrating power hand tools, representing tools commonly used in an automobile assembly plant, were studied. Spectra for the rotary and reciprocating power tools and had large distinct dominant fundamental frequencies occurring in a narrow frequency range between 35 Hz and 150 Hz. These frequencies corresponded closely to tool free-running speeds, suggesting that major spectral component frequencies may be predicted on the basis of speed for some tools.
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Ulin SS, Armstrong TJ, Radwin RG. Use of computer aided drafting for analysis and control of posture in manual work. APPLIED ERGONOMICS 1990; 21:143-151. [PMID: 15676770 DOI: 10.1016/0003-6870(90)90137-m] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Computer aided design (CAD) in conjunction with digitised anthropometric manikins can be used for analysis and control of stressful work postures, one of the most frequently cited occupational risk factors of upper extremity cumulative trauma disorders. This paper describes the use of macros for manipulating manikins and workstation components and for designing the workplace. AutoCAD, a popular computer aided design software package, was used to demonstrate the feasibility of these concepts. Specifically, macros are used for drawing work equipment using parametric designs, manipulating manikins and analysing jobs. In comparing the macros to the use of primitive CAD commands, the macros not only decrease the amount of time needed to create workstation components, but they also make the task easier for the user and decrease the risk of errors. Despite the limitation of anthropometric data and manikins, CAD is an effective method for identifying postural stresses and redesigning the workstation to control the identified stresses.
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Silverstein BA, Armstrong TJ, Longmate A, Woody D. Can in-plant exercise control musculoskeletal symptoms? JOURNAL OF OCCUPATIONAL MEDICINE. : OFFICIAL PUBLICATION OF THE INDUSTRIAL MEDICAL ASSOCIATION 1988; 30:922-7. [PMID: 3230441 DOI: 10.1097/00043764-198812000-00008] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
After 1 year of an on-job exercise program to control musculoskeletal symptoms in the neck and upper limb, there were no statistically significant differences in localized postural discomfort scores or in the proportion of those whose discomfort decreased based on exercise participation. Although no clear reduction in discomfort was achieved by the exercise program alone, at least 67% of respondents who participated in the exercise program reported that the program made them feel better.
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Armstrong TJ, Fine LJ, Goldstein SA, Lifshitz YR, Silverstein BA. Ergonomics considerations in hand and wrist tendinitis. J Hand Surg Am 1987; 12:830-7. [PMID: 3655257 DOI: 10.1016/s0363-5023(87)80244-7] [Citation(s) in RCA: 139] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The objectives of this article are to present (1) a historical perspective on hand and wrist tendinitis in workers, (2) new data that demonstrate a relationship between the repetitiveness and forcefulness of manual work and the prevalence of tendinitis, (3) possible biomechanical factors in tendinitis, and (4) possible job modifications for the prevention of tendinitis. Numerous studies during the last 100 years show that tendinitis is a major cause of worker suffering and workers' compensation in intensive hand work. Epidemiologic data show that the risk of hand and wrist tendinitis in persons who perform highly repetitive and forceful jobs is 29 times greater than in persons who perform jobs that are low in repetitiveness and force. A possible factor in this relationship is viscous deformation of the tendons and adjacent tissues. Although these data suggest that the risk of tendinitis among workers can be reduced by reduction of the repetitiveness and the forcefulness of the work, this hypothesis has not yet been fully tested.
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Armstrong TJ, Fine LJ, Radwin RG, Silverstein BS. Ergonomics and the effects of vibration in hand-intensive work. Scand J Work Environ Health 1987; 13:286-9. [PMID: 3324309 DOI: 10.5271/sjweh.2049] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Along with ergonomic factors, such as forceful and repeated exertion and certain postures, vibration has been cited as a factor of chronic nerve and tendon disorders such as carpal tunnel syndrome and tendinitis. The arguments for the contribution of vibration come from epidemiologic studies, clinical case analyses, and studies of short-term effects. It is well established that vibration stimulates muscle contraction, which is called the tonic vibration reflex. It is also known that vibration reduces tactility and that tactility affects the amount of force exerted to hold or manipulate a given object. For localized vibration exposure of the hand and arm to occur, the hand must grip a vibrating object. Vibration may increase the risk of chronic tendon and nerve disorders by increasing the force exerted in repetitive manual tasks. This close relationship between force and vibration, and difficulties in measuring force and vibration in manual work, makes it very difficult to determine their relative contributions in epidemiologic and clinical studies.
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Goldstein SA, Armstrong TJ, Chaffin DB, Matthews LS. Analysis of cumulative strain in tendons and tendon sheaths. J Biomech 1987; 20:1-6. [PMID: 3558424 DOI: 10.1016/0021-9290(87)90261-2] [Citation(s) in RCA: 98] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Twenty-five fresh frozen flexor digitorum profundus tendons stratified by sex were subjected to uniaxial step stress and cyclic loads in twelve intact human cadaver hands. By attaching specially designed clip strain gage transducers on tendons just proximal and distal to an undisrupted carpal tunnel, the interactions of the tendons, tendon sheath and retinacula were measured. The elastic and viscous response of the tendon composites to step stresses were found to fit fractional power functions of stress and time respectively. A significant and quantifiable decrease in strain from the proximal to the distal tendon segment was found to be a function of wrist deviation. The results indicate that an accumulation of strain does occur in tendinous tissues during physiologic loading.
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Abstract
Carpal tunnel syndrome (CTS) is the most commonly reported nerve entrapment syndrome. The prevalence of CTS among 652 active workers in jobs with specific hand force and repetitiveness characteristics was estimated. The prevalence of CTS ranged from 0.6% among workers in low force-low repetitive jobs to 5.6% among workers in high force-high repetitive jobs. When controlling for potential confounders, the odds ratio for the high force-high repetitive jobs was more than 15 (p less than .001) compared to the low force-low repetitive jobs. High repetitiveness appears to be a greater risk factor than high force (odds ratio of 5.5 p less than .05 versus 2.9 and not statistically significant).
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Silverstein BA, Fine LJ, Armstrong TJ. Hand wrist cumulative trauma disorders in industry. BRITISH JOURNAL OF INDUSTRIAL MEDICINE 1986; 43:779-84. [PMID: 3790459 PMCID: PMC1007752 DOI: 10.1136/oem.43.11.779] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
A total of 574 active workers from six different industrial sites were categorised into four force repetitive exposure groups. Workers in low force-low repetitive jobs served as an internal comparison population for the three other groups. Videotapes and surface electromyography were used to estimate hand force and repetitiveness. The presence of cumulative trauma disorders (CTD) was determined by structured interview and standardised non-invasive physical examination. Only workers who had been working on the study jobs for at least one year at the time of evaluation were eligible for selection. Categorisation of jobs and identification of CTDs were carried out independently by investigators who were appropriately blinded to exposure and outcome. The analysis of associations between CTDs and exposure categories were performed using Mantel-Haenszel plant adjusted odds ratios and unconditional multiple logistic regression. Significant positive associations were observed between hand wrist CTDs and high force-high repetitive jobs. These associations were independent of age, sex, years on the specific job, and plant.
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Fine LJ, Silverstein BA, Armstrong TJ, Anderson CA, Sugano DS. Detection of cumulative trauma disorders of upper extremities in the workplace. JOURNAL OF OCCUPATIONAL MEDICINE. : OFFICIAL PUBLICATION OF THE INDUSTRIAL MEDICAL ASSOCIATION 1986; 28:674-8. [PMID: 3746489 DOI: 10.1097/00043764-198608000-00027] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Surveillance for musculoskeletal disorders of the upper extremity in industry is in its infancy. Research efforts to elucidate the causal factors of these disorders often rely on either the analysis of existing medical records, worker compensation records (passive surveillance), or the surveying of workers with questionnaire and physical examination (active surveillance). The use of either type of data for routine surveillance presents several difficulties illustrated with the results presented in this paper. The analysis of existing records is generally less costly but the reliability of the data is difficult to assess. Standardized questionnaire and physical examinations can be as sensitive as the use of unusually thorough existing occupational medical records; however, it is unclear whether the additional cost of an active surveillance system will deter the routine use of such systems.
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Armstrong TJ. Ergonomics and cumulative trauma disorders. Hand Clin 1986; 2:553-65. [PMID: 3771659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Chronic tendon and nerve disorders of the upper extremity, such as tendinitis and carpal tunnel syndrome, are a common problem among persons who routinely perform hand-intensive work. This article summarizes the most commonly reported occupational risk factors: repetitiveness, forcefulness, certain postures, mechanical stresses, exposure to vibration, and exposure to low temperatures. It describes how to look for these factors and how to control them through the design of work equipment and procedures.
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McKenzie F, Storment J, Van Hook P, Armstrong TJ. A program for control of repetitive trauma disorders associated with hand tool operations in a telecommunications manufacturing facility. AMERICAN INDUSTRIAL HYGIENE ASSOCIATION JOURNAL 1985; 46:674-8. [PMID: 4072912 DOI: 10.1080/15298668591395526] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
This paper summarizes efforts to control the incidence and severity of repetitive trauma disorders associated with hand tool operations in a telecommunications manufacturing facility with 6,600 employees. Repetitive trauma disorders--including strains, tendinitis, ganglions and carpal tunnel syndrome--were the leading cause of lost time and workers' compensation expenses at this plant in 1979. The plant-wide incidence rate of OSHA reportable repetitive trauma disorders was 2.2 cases per 200,000 workhours and resulted in 1,001 lost workdays. Incidence rates as high as 4.6 were reported in some areas, but were believed to be much higher among persons who actually perform repetitive work in these areas. In the spring of 1981, the plant safety and health committee undertook a control program that included creation of a task force, a training program, improvements in the design of workstations and tooling, and management of restricted workers. During 1982, the incidence rate of repetitive motion disorders has decreased to .53 cases per 200,000 workhours and resulted in only 129 lost workdays.
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Radwin RG, Armstrong TJ. Assessment of hand vibration exposure on an assembly line. AMERICAN INDUSTRIAL HYGIENE ASSOCIATION JOURNAL 1985; 46:211-9. [PMID: 4003272 DOI: 10.1080/15298668591394680] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
This paper describes a study undertaken to evaluate and control vibration exposure associated with pneumatic screwdrivers used in an electrical appliance assembly plant. The study was motivated by management's concern about reports of cumulative trauma disorders in the upper extremities of workers who used pneumatic screwdrivers. Vibration exposure from power hand tools on an assembly line is difficult to predict due to highly variable conditions and techniques used between operators. Vibration exposure was measured using observation samples of tool vibration obtained on the assembly line for individual assembly tasks. Typical tool one-third octave band acceleration spectra estimated from laboratory measurements were used in conjunction with the measured exposure times to compare workers' risk of exposure to the hazards associated with operating vibrating hand tools. Characteristic vibration produced by the tools during phases of operation were separated and analyzed individually to identify and control the source.
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Abstract
Skin forms a link through which the forces required to hold and manipulate objects are transmitted from the musculoskeletal system to the objects; while these forces are necessary for most work, excessive forces can be injurious. This paper discusses some of the mechanical properties of skin and discusses how they are important in manual work. Recommendations for the design of hand-held objects and for future research are given.
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Armstrong TJ, Castelli WA, Evans FG, Diaz-Perez R. Some histological changes in carpal tunnel contents and their biomechanical implications. JOURNAL OF OCCUPATIONAL MEDICINE. : OFFICIAL PUBLICATION OF THE INDUSTRIAL MEDICAL ASSOCIATION 1984; 26:197-201. [PMID: 6716187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The purpose of this study was to investigate the pathological influence of mechanical stresses that occur inside the carpal tunnel during exertions of the hand. Microscopic changes in fibrous tissue density, in synovial, subsynovial, and adjacent connective tissue density, and in median nerve epineurium density, arteriole wall muscle thickness, and arterial and venule endoproliferation were investigated at 5-mm increments along a 9-cm range of six postmortem wrist specimens. All of these changes increased from normal in the proximal portions of the wrist, -30 to -40 mm from the wrist crease, to maximal values 0- to 20-mm distal to the wrist crease. The changes then decreased toward normal in the distal sections, 20 to 40 mm. The location and character of these changes suggest that repeated exertions with a flexed or extended wrist are an important factor in their etiology. The consistency with which they are found in this and other studies suggests that extreme changes associated with highly repetitive work or additional stress factors are required to produce symptoms in most cases of carpal tunnel syndrome.
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