Effect of design of two-wheeled containers on mechanical loading

Abstract

To prevent low back disorders due to lifting activities, occupational lifting tasks are being replaced by pushing/pulling tasks, for instance in refuse collection. Design factors of two-wheeled carts, such as centre of mass (COM) and handle location, might have a major impact on joint loading. We varied the (horizontal and vertical) COM and handle location of a two-wheeled container to test their effect on handle forces and joint loading during two-handed steady pushing and pulling. Net torques at the low back, shoulder and elbow were relatively low in the standard container design. Backward displacement of the COM increased low back loading and forward displacement of the COM increased shoulder and elbow loading. A COM displacement in the direction of the axis of the wheels did not have negative effects on joint loading and reduced the forces, needed to tilt the container. A 0.1 m increase of the handle height slightly reduced the required vertical force without adverse effects on joint loading. It is suggested that the design of Dutch two-wheeled containers can be improved by moving the COM of the loaded container in the direction of the axis of the wheels and by slightly raising the height of the handles. Relevance to industry The design of a two-wheeled container, used for refuse collection, might have a major effect on the risk of developing musculoskeletal disorders through mechanical overloading. In this paper the effect of two important design parameters on joint loading is investigated and interpreted in terms of optimising container design.