Quantifying repetitive hand activityfor epidemiological research on musculoskeletal disorders – part I: individual exposure assessment

Abstract

An exposure measurement approach is described for quantifying repetitive hand activity of individual workers in a prospective epidemiological study on work-related upper extremity musculoskeletal disorders. A total of 733 subjects were involved in this study at the baseline. Hand activities were quantified by force and repetition. Force levels were measured by workers' self-reports, ergonomists' estimates based on observation and measurements with instrumentation. Repetition levels were measured by detailed time–motion analyses using two repetitive hand activity definitions and ergonomists' estimates using scales for the American Conference of Governmental Industrial Hygienists hand activity level and the Strain Index. Results showed that the present exposure assessment approach seems to be able to quantify force level and repetitiveness of hand activities. Repetitive hand activity is quantified differently depending on whether forceful hand exertion or repetitive muscle activity is used as the definition. These hand activity definitions may quantify different physical exposure phenomena. Individual exposure assessment is important in epidemiological research of musculoskeletal disorders as there are interactions between the individual subjects and the measured parameters. These interactions may vary between exposure parameters.

Keywords:

• Individual exposure quantification
• Observational
• Self-reporting
• Direct measurement
• Repetition
• Hand force

Acknowledgement

We acknowledge the important contributions of Ruby Irving, Benjamin Hamilton, Cindy Orr, Jessica Keller, Larry Taing, Pat Woods, Tiffany Ballard, Hieu Pham, Christina Buntin and Nancy Caldwell in data collection and processing, Caroline Smith in coordination of field data collections, Joyce Fan for providing subject demographic information and Eira Viikari-Juntura for review of the manuscript. This research was funded in part by the US National Institute for Occupational Safety and Health (OH1007316) and the Washington State Department of Labor and Industries.