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An electromyographic study of strength and upper extremity muscle activity in simulated meat cutting tasks.
Appl Ergon 1997 Apr; 28(2):129-137
Electromyographic (EMG) changes in upper extremity muscles during a simulated meat cutting task were examined in 15 right handed male volunteers, mean age 26.1 years. Forces were applied to a straight cylindrical handle with the right hands using postures similar to those observed during meat cutting tasks at full arm's reach measured from the shoulder (position one, P1), at half the distance between P1 and the top of the shoulder with the arm at rest, at the level of the hand with the arm at rest and the elbow fully flexed (position three, P3), and at a level half the distance between P3 and the tip of the elbow. The handle was attached to the Number 50 Linear Motion Device of the LIDO WorkSET-II work simulator system. The forces were applied horizontally with respect to the handle and using postures simulating stab and slice motions. The forces were made at 50 to 100% maximum effort. EMG activity was recorded from surface electrodes attached to the posterior deltoid, biceps brachii, triceps brachii, extensor digitorum, and flexor-digitorum superficialis (FDS) muscles. The ratios of normalized EMG activity to the force produced during the exertion (EMG/force ratios) were computed for the various muscles under each experimental condition. Force level did not affect the EMG/force ratios except in the case of the FDS muscle. EMG activity of the FDS muscle decreased in proportion to the force produced during static grips. Across all muscles, force exertion capability was maximal and the EMG/force ratios were generally minimized when the subjects pulled down on the handle while in P1. For vertical cuts, the force output generally decreased and EMG activity increased as the height of the handle was lowered. When making horizontal cuts at full reach distance, the subjects were generally able to apply greater forces that were associated with lower EMG/force ratios. The stab grasp tended to require higher forces producing lower EMG/force ratios than the slice grasp. The authors conclude that these data indicate that handle position has a significant effect on the ability to exert force and the EMG/force ratio of all upper extremity muscles. The study data also support the view that musculoskeletal stresses associated with meat cutting can be altered by redesigning tools and workstations.
NIOSH-Author; Meat-handlers; Work-capacity; Posture; Electrophysiological-measurements; Muscle-function; Task-performance; Simulation-methods; Work-analysis; Meat-packing-industry; Ergonomics
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Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division