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Biomechanical investigation of lifting speed.
Proceedings of the Konz/Purswell Occupational Ergonomics Symposium, 1995 Apr; :79-85
A laboratory study was conducted to explore the effects of lifting speed on several predetermined biomechanical variables including total lifting time, peak speed of load, total net muscle work, total absolute net muscle work, work done to the load, time integral of sum of squared ratio of joint moment and strength, total absolute joint moment, and the time when the peak speed occurs. Five subjects performed lifts at five lifting speeds labeled as the slowest, slow, normal, fast, and fastest, and three weights, 50%, 65%, and 80% of their maximum acceptable weight of lift. The speed at each level was determined individually by each subject according to their capability. Measures of the total work, total absolute net muscle work, work done to the load, and time integral of sum of squared ratio of joint moment and strength decreased significantly as the lifting speed increased (p<.05, <.001, <.001, <.001, respectively). This indicates that lifting at a faster speed tends to reduce the work the body has to do. The peak speed of load occurred at 70% of total lifting time for the slowest lifts, but at 30% of total lifting time for other lifting speeds. Performing lifts at their minimum speeds changed the usual speed coordination technique the subjects used. The study suggests that slow lifting may not necessarily be of advantage to the body.
Ergonomics; Manual-materials-handling; Humans; Human-factors-engineering; Musculoskeletal-system-disorders
Proceedings of the Konz/Purswell Occupational Ergonomics Symposium
Department of Industrial Engineering, Texas Tech University, Lubbock Texas