Postural Stability Assessment during Manual Material Handling Tasks – Case Study

Azevedo, Rui; Martins, Cristina; Sá, Maria Manuel; Teixeira, José; Barroso, Mónica

http://hdl.handle.net/10400.24/1907

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Abstract(s)

Human body is a system of segments connected by joints; any voluntary motion of the body causes internal perturbation of balance. Manual handling of loads such as load lifting may increase these perturbations. In a bi-manual whole body lifting task, the grasp of a load and pick it up from the floor induces a forward shift in the position of the centre mass, challenging the dynamic balance regulation while simultaneously impending the ongoing extension movement. In order to compare the disturbance of balance both in back lifting or leg lifting of a frontal load a laboratory-based case-study was performed through the simulation of lifting tasks. A twenty-eight male worker frontally lifted a box from the floor. Two experimental conditions were applied: the participant used leg lift (straight back, bent legs) or back lift (straight legs, bent back) with combinations of two different weight materials. Through the application of the Index of Proximity to the Stability Boundary it was found that both techniques adopted for load lifting seem to equally influence postural balance control. In addition, it was concluded that manual lifting of heavier loads may jeopardize postural balance increasing the occurrence of falls.