Quantifying Forceful Manual Exertions in Industry

Research Trainee: Matthew Marshall, PhD Student, Dept. of Industrial and Operations Engineering at the University of Michigan

Faculty Researcher: Thomas J. Armstrong, PhD, Professor of Industrial and Operations Engineering and Biomedical Engineering at the University of Michigan

Forceful hand exertions are a recognized risk factor for the development of Work Related Musculoskeletal Disorders in the upper extremity. The need for measuring and quantifying hand force during manual exertions is widespread, but there currently are few user-friendly tools. This project will investigate, develop, and improve a hierarchical system of tools for measuring hand forces. First, the study will examine the use of electromyographic (EMG) techniques for estimating hand forces in dynamic work. The relationship between EMG calibration techniques and the EMG-force curve will be studied for non-isometric exertions. The goal is to determine which calibration technique produces the most accurate relationship between EMG signal parameters and the actual magnitude of the manual exertion. Second, the study will investigate the ability of workers and job analysts (observers) to subjectively discriminate among different levels of hand force. Finally, an observer-based force rating methodology will be developed and validated. This system will have applications in 1) basic ergonomic job analysis to assess risk factors for upper extremity MSDs, and 2) rehabilitation job analysis to accommodate the forceful demands of a job with an injured or disabled worker’s ability to perform manual exertions. This system will use benchmarks of forceful exertions of varying magnitudes selected from common occupational and non-occupational work activities. A combination of laboratory experiments and field surveys will be used to achieve the research goals.


Publications resulting from this project:
Marshall MM, Armstrong TJ, Ebersole ML. Verbal estimation of peak exertion intensity. Human Factors. 2004;46(4):697-710.

Marshall, M.M. and Armstrong, T.J. Observational assessment of forceful exertion and the perceived force demands of daily activities. Journal of Occupational Rehabilitation. 2004;14(4):281-294, 2004.


Research trainee’s current position:
Matthew Marshall completed his PhD in 2002 and is currently the Associate Dean Undergraduate Programs and a Professor at the Kate Gleason College of Engineering, Rochester Institute of Technology.