Trunk force development during static and dynamic lifts.
Hum Factors 1987 Feb; 29(1):19-29
The activity of the back musculature, and therefore the loading of the spine, were evaluated in 45 human male subjects performing tasks involving the exertion of force about the spine in a manner simulating lifting. The subjects, who were aged 17 to 61 years, were all healthy with no history of chronic low back disorder. Independent experimental variables in this study were trunk angle and trunk angular velocity. Dependent variables included: the maximum voluntary torque that a subject could exert about the lumbosacral junction during the return from a flexed trunk posture; the integrated electromyography (EMG) of the right latissimus dorsi muscle; the integrated EMG of the right erector spinae muscle; and the integrated EMG of the left erector spinae muscle. The subjects were required to exert torque about their low back under both static and dynamic lifting conditions. Results indicated that significantly greater loading occurs under slow dynamic conditions than under static conditions. A significant increase in the correlation between torque and muscle EMG in the erector spinae muscles as trunk velocity increased was also observed. A regression model was described which analyzes trunk loading as a function of trunk angle and velocity. The authors conclude that static models are inappropriate indicators of dynamic trunk load.
NIOSH-Publication; NIOSH-Grant; Physiological-measurements; Muscle-stress; Muscle-tension; Musculoskeletal-system; Back-injuries; Simulation-methods
William S. Marras, Industrial and Systems Engineering Department, Ohio State University, Columbus, OH 43210
Industrial and Systems Engr Ohio State University 1971 Neil Anveue Columbus, Ohio 43210