Citation

Marras WS. Int. J. Ind. Ergonomics 1987; 1(3): 159-167.

Copyright

(Copyright © 1987, Elsevier Publishing)

DOI

unavailable

PMID

unavailable

Abstract

The time dependent aspects of trunk muscle activation are of utmost importance when evaluating the loading of the spine during lifting. If all spine supporting muscles reach peak force simultaneously during a lift, the effects upon the spine would be much different than if the forces activated sequentially. This research has studied the recruitment and peak activity pattern of the back musculature as well as their association with trunk supporting force production. Forty-five subjects were evaluated in this effort under static and controlled dynamic conditions. Most recruitment delays between signals were similar except between the muscles and torque. However, significant peak delays were noted among all experimental conditions. Generally, when the trunk exerted lifting force under static conditions, the peak time delays were similar to a dynamic lift of 30 deg/s. Dynamic lifts of 15 deg/s resulted in much longer peak time delays between signals whereas dynamic lifts of 90 deg/s resulted in very short peak time delays. The biomechanical significance of these findings is discussed.