Load spatial pathway and spine loading: how does lift origin and destination influence low back response?

While heavy lifting has been identified as an important risk factor for low back disorders, little is known about workplace spatial layout - the relative positions of shelves and the impact of this on spine loads. The objective of the current study was to investigate how the relative positions of the load origin and destination impact three-dimensional spine loads. Seven females and seven males lifted an 11.4 kg box from an origin shelf to a destination shelf, each defined by height (elbow, knee and shoulder level) and asymmetry (608 clockwise, sagittally symmetric, 608 counter-clockwise) while their spine loading was assessed by an electromyographic-assisted model. The results indicated that the starting and destination heights and starting task asymmetry all had significant impact on spine compression (with an increase of between 400 and 1900 N when compared to the most neutral position) and lateral shear (with a 100 to 150 N increase) while the destination height impacted the anterior - posterior shear forces (with up to 400 N increase). The results of the current study emphasize the importance of proper workplace spatial layout, specifically the importance of specifying starting position of the load relative to the destination. Adjustment of the starting position will impact the three-dimensional spine loads while the destination height and asymmetry influence the shear forces. Furthermore, the influence of the specific pathway ( origin relative to destination) indicates there may be a potential preparatory muscle response leading to the loads on the spine. Thus, the pathway of the box plays an important role in the spine responses during lifting, in that longer and non-neutral pathways increase spine loads indicating the importance of the relative position of the origin and destination shelf.