Work related musculoskeletal disorders (WMSD) remain the focus of research efforts as costs associated with these disorders range from 13 to 54 billion dollars annually. WMSDs associated with the back and neck compromise almost 27% of all reported WMSDs. Approximately 1/3 of visual display terminal (VDT) operators report back and neck pain annually (BLS, 1998). Physical risk factors of VDTs associated with low back and neck WMSDs include static work postures and workstation design. The objectives of this study were to assess the effects of monitor height, chair type and their interaction on task performance, back/neck electromyography (EMG), perceived discomfort, and number of posture shifts. Both monitor height and chair type were assessed using two levels (high and low). Participants, four male and four female college age students, performed two data entry tasks using a standard keyboard and monitor and a fully adjustable bi-level table. In addition to the experimenter defined workstation configurations, participants were allowed to adjust their workstation to their preferred settings. Analysis of variance was performed to assess differences in task performance, perceived level of discomfort, number of posture shifts, and EMG data associated with various combinations of monitor height and chair type. Correlation analysis was performed to assess the relationship between participant's perceived discomfort and measured muscle activity to help determine if these two measurements could be used interchangeably to assess workstation design.
No effect of workstation configuration (monitor height/chair type) was found for the majority of dependent variables. An exception was that configuration of low monitor, high chair, and their interaction generated significantly more muscle activity for the low back. User preferred settings were not found to differ significantly from those investigated with respect to muscle activity, perceived discomfort, posture shifts, and performance. Additionally, it was found the participants chose to position the iii workstation according to guidelines suggested in the literature for reducing WMSD discomfort.
Task effects were found for performance, posture shifts, and perceived level of discomfort. Higher levels of performance and posture shifts for the neck were associated with the typing task, as opposed to the math task. Higher levels of neck discomfort, posture shifts of the feet and posture shifts of the back were associated with the math task.
Correlation analysis provided evidence that perceived discomfort reported by participants and muscle activity for job tasks may not be related. Observed muscle activity for the tasks investigated in this study was low and in some instances, close to resting activity. Due to low levels of EMG, participants may not have been cognizant of their back and neck muscle activity, offering an explanation for why participants experience a cumulative effect of workstation design and seated postures, but linking particular causal factors to the development of LBP and NP is difficult.
The findings of this study suggest that there are no gross physical differences between the chair types or monitor heights as defined in this study. Other factors (such as user preferences, job task demands, specific chair parameters, etc.) may significantly effect chair selection. This study found that task was a significant effect for the majority of dependent variables, and therefore may need to be a major factor driving workstation design. Workstation configuration will help determine the type of static posture assumed at a workstation, but the "discomfort or number of posture shifts" associated with that workstation and posture might be more a result of the job task requirements. / Master of Science
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/35013 |
| Date | 17 September 2001 |
| Creators | Stanfield, Jennifer Renee |
| Contributors | Industrial and Systems Engineering, Babski-Reeves, Kari L., Nussbaum, Maury A., Kleiner, Brian M. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | Thesisfinal2.pdf |
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