Amplified Trunk-Head Contribution to Whole-Body Angular Momentum Under Perturbed Conditions

<title>Abstract</title> <p>The study’s objective was to establish whether and how the contributions of different body segments to whole-body angular momentum are reorganized 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 &lt; 0.001) and lower limb contributions significantly decreased (p &lt; 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 (p &lt; 0.001) to the increased peak-to-peak range of whole-body angular momentum, indicating enhanced involvement in whole-body angular momentum control 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 serve as an important compensatory mechanism for controlling whole-body angular momentum in the frontal plane during perturbations. The findings could develop preventive treatments by implementing trunk coordination strategies to enhance stability control.</p>