An electromyographic investigation of asymmetric lifting and moving of a load: I. Effects of load lift from floor to target shelves

Abstract

AbstractThe range of normalized electromyography (EMG) values when lifting and moving a 5.84 kg box was between 0.12 and 0.77. The right iliocostalis and the right and the left external obliques showed significant increases in muscle activity at 90° of asymmetry. The average percentage increase for the stated muscles was 62.3% when compared to muscle activity at 0°. The left external oblique also responded significantly at 60° of asymmetry when compared to 0°. The knuckle, sternum, and reach heights significantly affected the left iliocostalis and the left and right erector spinae muscles. The average percentage increases in the stated muscles were 74.4% at knuckle height, 126.1% at sternum height, and 143.3% at reach height, when compared to floor level. Significant increases in muscle activity for the right iliocostalis and the right external oblique were registered only at the sternum and at the reach heights. For manual materials handling (MMH), an endeavor should be made to avoid asymmetric lifting and moving at 90° and from the floor level and to the reach height. To minimize the risk of back injury, the MMH task should be performed preferably within an asymmetry of 30° but not exceeding 60° asymmetry. © 2009 Wiley Periodicals, Inc.