Top-down estimation of joint moments during manual lifting using inertial sensors

L5/S1 moments during manual lifting tasks have often been assessed in the laboratory either from a bottom-up approach, that is using one or more force plates measuring ground reaction forces (GRFs) and an optoelectronic system measuring positions and orientations of lower body segments up to L5/S1 joint (e.g. Plamondon et al., 2010), or from a top-down approach, that is using an instrumented box to measure hand forces and an optoelectronic system measuring positions and orientations of upper body segments and trunk down to L5/S1 joint. The usability of such systems for field measurements is limited by the restricted measurement volume of the optoelectronic system and the constraints imposed by the force plates. As a possible alternative, the use of inertial sensors for measuring segment kinematics combined with instrumented shoes to measure GRFs has been proposed (Faber et al., 2010), but has not been evaluated. However, a bottom-up approach using inertial sensors with force plates has been evaluated for lifting tasks, and a top-down approach for a carrying task with limited trunk motion (Kim and Nussbaum, 2013). To the authors’ knowledge, however, use of a top-down approach with inertial sensors has yet to be evaluated for a lifting-lowering task. This study thus aimed to assess the ability of a top-down approach using inertial sensors in conjunction with an instrumented box to measure hand forces for the quantification of the L5/S1 joint moment in a lifting-lowering task. Results of this study are intended to contribute to the development of a method based on inertial sensors for assessing manual materials handling tasks in the field.