Browsing by Subject "ergonomics"
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Item Computer Related Illness: the Importance of the Physical Human-Machine Interface(Law Enforcement Management Institute of Texas (LEMIT), 1994) Patterson, Don L.Item Design guidelines and evaluation of an ergonomic chair feature capable of providing support to forward-leaning postures(Texas A&M University, 2005-02-17) Stevens, Edward MartinThis research investigated the need, design, and evaluation of a product capable of providing support to forward-leaning postures. Due to the high occurrence of low-back pain in industry potentially due to workers performing their tasks while assuming forward-leaning postures, along with the biological plausibility of these postures causing low-back pain, the need was established for a product that provides forward-leaning support. An envelope was quantified, ranging from the 5th percentile female to the 95th percentile male, to establish the range of potential forward-leaning postures. The design of a Support-Arm for use with current ergonomic chairs was discussed and design feature specifications were then provided. A Latin Square statistical design was employed to evaluate a Support-Arm model alongside 8 other commonly used chairs over 3 different postures. Subjects, overall, had lower peak pressures for the buttock-thigh region, increased productivity, higher comfort levels, and higher buttock-thigh contact areas when seated in the Support-Arm model chair as compared to the other chairs. Subjects, overall, also ranked this chair first over the other chairs for preferred use after having sitting experience in all 9 chairs. In an additional part of the evaluation, subjects chose their own set-up of the Support-Arm model chair. Eleven of the 18 subjects chose to use the Support-Arm when their workstation was located 36? above the floor. Subjects confirmed the need to design a Support-Arm capable of providing forward leaning support to the entire envelope of forward-leaning postures. Statistical evaluation revealed several significant differences between the chairs. The results gave no indication that the use of a Support-Arm for forward-leaning support may cause detrimental effects to users or overall chair ergonomics. Future research could track workers? use of a Support-Arm in industry and compare their occurrence of low-back pain to a control group.Item Test re-test repeatability of the strain index(Texas A&M University, 2004-09-30) Stephens, John-PaulThe Strain Index (SI) has repeatedly shown high levels of validity for differentiating between safe and hazardous tasks for the distal upper extremity (DUE). One limitation of the SI is the lack of reliability data. This study was designed to evaluate the test-retest repeatability of the SI. Fifteen raters, divided into five teams of three, were asked to use the SI to analyze 73 video AVI files of different job tasks; initially as individuals and then as teams. Several months later, raters were asked to repeat individual and team job task assessments. Raters were instructed to analyze tasks using five of six SI task variables, while the sixth was held constant. For three of these task variables, additional data was collected such as peak force and duration of job cycle. Test-retest repeatability was measured using Pearson's R, Spearman's rho, and tetrachoric correlation according to the nature of the variable. Spearman's rho values for individual and team task variable ratings ranged from 0.68 to 0.96 (0.88 average). Pearson's R for task variable data ranged from 0.76 to 0.99 for both teams and individuals with an average of 0.91. The Strain Index's rho values for individuals and teams were 0.70 and 0.84, respectively. For hazard classification, the tetrachoric correlation for individuals was 0.81 and 0.88 for teams. Results of this study support the conclusion that the Strain Index is repeatable when used by teams as well as individuals.Item The development of an index for the proximal upper extremity(Texas A&M University, 2006-08-16) Walline, Erin KuruszAnalysis techniques specific to the proximal upper extremity have historically been overlooked in the field of ergonomics. This research effort provides a methodology that will allow the ergonomics practitioner to analyze a job and predict whether or not that job exposes workers to increased risk of proximal upper extremity disorders. Literature from the fields of physiology, biomechanics, and epidemiology was assimilated in order to understand the theories of pathogenesis of disorders in the rotator cuff and to identify the risk factors associated with proximal upper extremity disorders. A retrospective epidemiological study was conducted to identify job task variables that may contribute to the occurrence of proximal upper extremity disorders. Two proximal upper extremity constructs were proposed: a fatigue-based model and a compressive load-based model. The constructs incorporated lessons learned from the literature and results from the epidemiological study. Validation of the models was performed using data from the epidemiological study. It was determined that the fatigue-based model was a good predictor of proximal upper extremity disorders.Item The obese office worker seating problem(2009-05-15) Benden, Mark E.A field study was performed using 51 participants that were randomly selected from several Brazos Valley, Texas businesses to participate in an 8-hour assessment of office seating habits that influence seating design and testing. A control group was established as those with BMI?s < 35 and an obese group was established as those with BMI?s >35. Data was collected through written survey and through data logging of seat and back contact pressure (average and peak), surface area, center of gravity and duration of contact by recording 8 metrics, once per second using the X-sensor pressure mapping device and software. Additionally, 50 days of caster roll distance was recorded for the participants using a caster mounted digital encoder. It was determined that at alpha = 0.05, using the Student?s T-test, a significant difference did exist between the groups in mean seat time per shift (p<.001) back contacts per shift (p<.002), seat contacts per shift (p<.01) and caster distance rolled per shift (p<.001). During a subsequent lab study, data were collected during 3 cycles of ingress, egress on the armrest use, along with anthropometry and critical chair testing parameters. Center of Gravity was measured from a fixed backrest (front to rear) for 16 participants. 4 male and 4 female obese with BMI greater than 35 and 4 male and 4 female with BMI less than 30 were compared. The purpose of this study was to determine whether a significant difference existed between anthropometric factors for normal and obese participants that would affect how a chair should be loaded during testing. The null hypothesis that normal means and obese means for each measure were equal was rejected by using independent samples T-test at alpha = 0.05 with p<.001 significance reported for all measures. These data suggest a need for a fresh look at several parameters used in the normal test standards as well as a need for a tougher test method for seating designed for the obese worker.Item Washington State Ergonomics Tool: predictive validity in the waste industry(Texas A&M University, 2004-09-30) Eppes, Susan EliseThis study applies the Washington State Ergonomics Tool to waste industry jobs in Texas. Exposure data were collected by on-site observation of fourteen different multi-task jobs in a major national solid waste management company employing more than 26,000 employees. This company has nationwide operations, and these jobs represent the majority of workers involved in the collection and processing of solid waste. The WSET uses observational checklist methodology to evaluate generic risk factors in the following six major categories: awkward posture, highly repetitive motion, high hand force, repeated impact, lifting, and hand-arm vibration. The assessment tool incorporates these risk factors and combinations of risk factors into checklists for identifying three levels of potential exposure: safe, -caution zone" and -hazard zone" jobs. The tool was developed for employers to use in determining whether a job was likely to increase the risk of workplace musculoskeletal disorders (WMSDs) to their employees. OSHA 200 logs were used as the main source of morbidity data. If there was one recorded WMSD, the job was classified as -positive. "If there was no recorded WMSD, the job was classified as -negative. "-Safe"jobs were those predicted not to expose workers to increased risk of WMSDs. Those that possessed one or more -caution zone"criteria but still fell below the -hazard zone" threshold required the employer to provide -awareness education" for employees and to further analyze the job for the presence of -hazard zone" risk factors. If hazard zone risk factors were not present, no further action was required. Jobs that upon further analysis possessed one or more of the -hazard zone"criteria were labeled -hazardous" jobs. If the further analysis shows the presence of risk factors established in the hazard zone criteria (Appendix B), the employer would be required to take corrective action to reduce exposures to below the hazardous level. Of the three jobs predicted to be -safe"by -caution zone" criteria, two did not have injuries and one did. Of the eleven jobs predicted by -caution zone"criteria to increase the risk of WMSDs, six resulted in injuries and five did not. Of the four jobs predicted by -hazard zone"criteria to be -problem"jobs, two jobs did result in injury and two did not. This study found that the WSET -caution zone"criteria were more effective at predicting which jobs were likely to increase the risk of WMSDs than was the -hazard zone"checklist. The caution zone had high sensitivity and low specificity. The hazard zone criteria reflect a low sensitivity and a low specificity. Further analysis revealed the WSET was helpful in predicting back injuries associated with lifting but not effective at predicting jobs with the potential for upper extremity injuries.