Three-dimensional peak and cumulative L4/L5 spine loads and trunk postures during non-occupational tasks

Cumulative low back loading has been shown to be a risk factor for low back pain reporting in the workplace. Evaluation of tasks outside of work might offer insight into why workers continue to have low back pain and may report pain differentially even when doing the same job. This study utilized a video-based 3D posture sampling approach to document joint postures of 18 people over a 2-hour period while performing non-repetitive tasks in and around their own homes. A 3D rigid link segment model was used to calculate reaction forces and moments at L4/L5 and joint models were used to calculate joint forces. Average peak (4.0 kN) and cumulative (9.9 MN·s) compression force estimates indicate significant loads on the low back occur during non-occupational tasks, despite the fact that participants spent most of their time (86.2%) in neutral trunk postures. Cumulative anterior reaction shear force (440 kN·s) was found to be comparable to those documented for a wide variety of occupational tasks, when extrapolated to an 8-hour shift. To our knowledge, this study is the first to include a full complement of 3D low back forces and moments, in conjunction with an assessment of trunk posture, for non-occupational activities. The evidence suggests that considering 3D peak and cumulative low back loading during non-occupational tasks is warranted and may help to explain some of the variability in the reporting of workplace-related low back disorders despite extensive ergonomic intervention.