Trunk muscle co-activation and activity in one- and two-person lifting

This study examined the effect of one-person and two-person team lifting on trunk muscle co-activation and activity and correlated them with the forces at lumbar spine at different risk levels. Eleven healthy subjects performed lifting tasks in the sagittal plane alone and together with another person matched by gender, anthmpometry, age, and strength at low, medium at high risk level according to the NIOSH equation. Our results showed that two-person team lifting reduces of the trunk muscles co-activation and activity compared to one-person lifting regardless of the level of risk. Moreover, in one-person lifting co-activation and muscle engagement increase with the forces on L5/S1 joint, while in two-person team lifting some correlations disappear, probably indicating that the muscular involvement in teams does not necessarily increase with risk level. Therefore, two-person team lifting could be recommended as one of the possible ergonomic interventions to reduce workers' biomechanical risk in industry activities in which manual lifting cannot be avoided.