ABSTRACT
Pushing and pulling (push-pull) activities involves static or dynamic muscular force exertions for moving or stabilizing objects. Neither the direction of the force nor the motion of the object need be perfectly linear or in the horizontal plane so long as deviation is small. In cases where the deviation is great, the exertion can be considered a hybrid of two types, such as lift-push, lift-pull, etc. as used by Pheasant et al. (1982). Push-pull activities occur in many types of work environments — shipping and receiving, moving, warehousing, agriculture and farming, retailing, etc. — and are becoming more common as a result of efforts to minimize lifting, lowering, holding, and carrying, the most debilitating and costly manual materials handling (MMH) activities. Baril-Gingras and Lortie (1990), in studying over 900 tasks, estimated that nearly half of all materials handling activities were push-pull ones. However, push-pull activities also account for a significant amount of overexertion musculoskeletal disorders (NIOSH, 1981; Klein, Jensen, and Sanderson, 1984; Troup and Edwards, 1985), accounting for approximately 20% of all back injuries from MMH activities.
