Amplified trunk-head contribution to whole-body angular momentum under perturbed conditions

The study’s objective was to establish whether and how the contributions of different body segments to whole-body angular momentum are modulated during unperturbed level walking, unpredictable and adapted drop-like perturbations and hole negotiation gait. Whole-body kinematics were recorded for 18 participants using an infrared motion capture system (250 Hz) and segmental and whole-body angular momentum were calculated in the sagittal, frontal, and transverse planes across three consecutive steps: preparation, perturbation, and recovery. Compared to level walking, trunk-head segment contributions significantly increased ( p < 0.001) and lower limb contributions significantly decreased ( p < 0.001) across all planes following both drop-like perturbations and hole negotiation gait, with the greatest modulation observed during unpredictable perturbations. Furthermore, the trunk-head segment’s contribution was associated with the increased peak-to-peak range of whole-body angular momentum ( p < 0.001), indicating functionally relevant involvement in regulating whole-body angular momentum under perturbed conditions. Given that the trunk-head segment contributes most to frontal plane whole-body angular momentum (~ 50%) and considering the rapid increase in frontal plane angular momentum following unpredictable drop-like perturbations, trunk movement may be important for controlling whole-body angular momentum in the frontal plane during perturbations . The findings could be used to develop preventive treatments by implementing trunk coordination strategies to enhance stability control.