Investigation of forces at the low back modeled with input of measured hand forces during the pull phase of a lifting task.
Danz ME; Ayoub MM
Advances in industrial ergonomics and safety III. Karwowski W, Yates JW, Mital A, eds. New York: Taylor and Francis, 1991 May; 3:279-283
Forces at the low back region exerted during a floor to knuckle height lifting task were investigated using a biomechanical model which used hand forces applied to the load as additional input. Five young men participated. Two experiments were designed to investigate the effects of speed of lift (normal and fast), frequency of lift, load in terms of percent maximum acceptable weight of lift (MAWL), and weight on the measured peak hand forces applied to the load. Lift frequencies were 1, 4, and 8 lifts per minute. Load was 35, 60 or 85% MAWL. Weights were 6.25, 10.91, 15.45, 20.00, and 24.77 kilograms. Strain gauges were used to measure the loads, and synchronized with a video camera system. Kinematic, anthropometric and load data, as well as hand forces, and forces at L5/S1 were calculated using the Dynalift model. Results showed that the peak measured hand forces did not carry through to affect L5/S1 compression and shear for each of the lifting conditions, but in the model, the introduction of hand forces caused a corresponding peak in L5/S1 compression and shear forces. Lifting only 35% MAWL at fast speed resulted in dangerous compression forces with respect to the tolerance limit of the spine. The increase in peak magnitude of compression and shear when modeled with input of measured hand forces was significant for fast speeds of lifts. The authors conclude that measured hand forces are greater than modeled hand forces, and that peaks in hand forces result in increases in shear and compression forces at L5/S1.
NIOSH-Grant; Musculoskeletal-system-disorders; Back-injuries; Biomechanics; Ergonomics; Mathematical-models; Manual-lifting; Physical-stress; Skeletal-stress
Industrial Engineering Texas Tech University PO Box 4130 Lubbock, TX 79409
Karwowski W; Yates JW; Mital A
Advances in industrial ergonomics and safety III. Proceedings of the Annual International Industrial Ergonomics and Safety Conference held in Lake Tahoe, Nevada, 10-14 June 1991. The Official Conference of the International Foundation for Industrial Ergonomics and Safety Research
Texas Tech University, Lubbock, Texas