The influence of transfer distance and pace of work on foot positioning strategies and low back loading in a manual material handling task

Foot positioning strategies are a key parameter in manual materials handling. The objective of this study was to assess the effects of transfer distance, pace and foot positioning on low back loading. Sixteen handlers performed a free handling task with conditions of pace (self-selected and 25% faster), distance (1.5 m, 1.0 m and 0.5 m), height (near-ground and above-waist levels), and mass (10 kg and 20 kg). A linear mixed model was used to evaluate the effects of mass, distance, pace and height on foot positioning occurrences. A non-parametric test (nparLD) was used to evaluate the effects of Pace x Foot positioning and Distance x Foot positioning on L5/S1 sagittal and asymmetrical moments. Positioning the feet aside from the lifting pallet was more prevalent when transferring at shorter transfer distances, high lifting height, and faster pace. When the feet were oriented aside the lifting area, asymmetrical peak moments were slightly higher when transferring at short distance. Facing the lifting pallet may ensure load symmetry, but orienting the feet aside may help to adapt to fast pace or short transfer distance.