Affiliations: [a] University of Wisconsin-Milwaukee, Milwaukee, WI, USA | [b] University of Utah, Salt Lake City, UT, USA
Correspondence:
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Address for correspondence: Arun Garg, Professor and Chair, Director, Center for Ergonomics, Industrial & Manufacturing Engineering, University of Wisconsin-Milwaukee, P.O. Box 784, Milwaukee, WI 53201 USA. Tel.: +1 414 229 6240; Fax: +1 414 229 6958; E-mail: arun@uwm.edu
Abstract: A laboratory study was conducted to determine the maximum voluntary strength (MVC) and maximum voluntary torque for one-handed lift and hold and hold only tasks as a function of shoulder posture. Twelve female volunteers of 21–33 years of age, claimed to be in good physical health and stated they had never had any musculoskeletal or cardiovascular problems participated in the study. One-handed maximum voluntary strength was defined as the maximum weight that a subject could lift and hold for 4 seconds (lift and hold) or hold the weight for 4 seconds without lifting from table height (hold only). MVC was measured in six different postures most commonly used in automobile assembly: 0/90 (shoulder flexion angle=0° and included elbow angle=90°), 30/90, 60/90, 90/120, 120/150, and 150/180. An analysis of variance showed that hold only MVCs were significantly higher than lift and hold MVCs by an average of 26%. Shoulder posture had significant effect on both types of MVCs. The strongest posture was 0/90 and the weakest posture was 90/120. There was large variability between subjects and some subjects had maximum shoulder strength as low as 4.3 kg. The findings of this study indicate that female have very low shoulder strength especially for jobs requiring overhead work.
Keywords: Shoulder posture, overhead work, maximum voluntary strength, maximum voluntary torque
