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An ergonomics assessment methodology for work-worker systems.

Sommerich CM
Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, K01-OH-000169, 2004 Aug; :1-112
Typically the goals of ergonomic research are one or more of the following: establish a (causal) link between hazards and health outcomes; characterize dose-response relationships between hazards and health outcomes; identify exposure thresholds for hazards; or demonstrate efficacy of interventions. Efforts persist towards all these goals, in continued attempts to understand the etiology of musculoskeletal injuries. Multi-factorial investigations are the best type of design for studying these complex problems that may involve biomechanics, psychosocial elements, work organization, and personal attributes. The objective of this project was the development and application of a comprehensive assessment methodology for characterizing the work-worker system from an ergonomics perspective. The methodology was applied to mobile computing, an emerging area of office ergonomics. This group was chosen, because it is anew grouping of workers, which presents the: opportunity for proactive, prospective investigation. The study was designed in three phases, the first of which provided qualitative information about the workers and their work conditions. In this study, the workers were professionals who used computers as a primary work tool. Both notebook computer users and desktop computer users were studied, in order to determine whether or not notebook users had similar or different problems than did desktop users. The second phase provide quantitative e data, exact measure of computer inputting activity over an extended period of time. The third phase was designed to investigate, in a controlled environment, some of the biomechanical effects of the work conditions that were reported through the first two phases of the study. The questionnaire phase revealed no differences in computer-use-related discomfort between notebook and desktop computer users. Body part discomfort was more prevalent in female participants than in male participants (consistent with findings of other researchers). In both groups of computer users, there were associations found between awkward working postures while using a computer and the frequent experiencing of physical discomfort associated with using a computer. Discomfort was also related to the propensity for sitting for uninterrupted extended periods of computer use time. In addition to these factors, notebook users were found to be at greater risk for frequent discomfort related to computer use if they used the computer without any peripheral devices. Further, there is a materials handling component to working with a notebook computer which was found to be directly related to body part discomfort. Particular modes of moving the notebook computer were related to the experience of discomfort in certain body parts. It had been consistently reported that computer users overestimate the time they spend working on their computers. As such, in order to best understand the physical interaction of the user with his/her computer, a software tool that captures inputting activity was utilized to directly measure inputting activity, by event (keystrike, mouse click, etc) and activity time. The key finding from this part of the study was the great amount of variation in day-to-day use of the computer in this group of workers, and the variation in patterns of activity and inactivity throughout the day. Expressions of these patterns may be more useful that averages of usage in determining why some computer users experience discomfort associated with computer use while others do not. The third phase of the study investigated two alternatives to working with a notebook computer in a stand-alone configuration. Based on considerations of the effects of the different conditions on the participants' biomechanics, productivity, and preferences, and the findings from the questionnaire, recommendations are made that notebook computers not be used in a stand-alone configuration, when working for an extended period of time, such as when a notebook is used in a desktop replacement scenario.
Muscular-disorders; Musculoskeletal-system; Computers; Computer-equipment; Work-areas; Work-operations; Ergonomics; Humans; Musculoskeletal-system-disorders; Injuries; Injury-prevention; Cumulative-trauma-disorders
Publication Date
Document Type
Final Grant Report
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Fiscal Year
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NIOSH Division
Priority Area
Research Tools and Approaches: Exposure Assessment Methods
Source Name
National Institute for Occupational Safety and Health
Performing Organization
North Carolina State University, Raleigh, North Carolina
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division