Sensorimotor Adaptation during Treadmill Walking under Tray Stabilization Demands: Selective Reorganization of Task-Related Movement Components

Introduction & Purpose Human locomotion results from dynamic coordination between whole-body movement organization and task-dependent sensorimotor control. When walking is combined with an object-stabilization task such as carrying a tray with a water-filled cup, the motor system must simultaneously regulate gait and stabilize the transported object. According to Optimal Feedback Control Theory (Todorov & Jordan, 2002), such multi-objective demands are expected to modify control priorities, leading to selective reorganization of movement coordination rather than global disruption of locomotor structure. Principal Movement Analysis (PMA), based on principal component decomposition of kinematic data (Federolf et al., 2013), provides a data-driven framework to identify coordinated movement structures and their modulation under varying task constraints. This study investigated whether carrying a water-filled cup induces selective adaptations in movement coordination and whether task-related movement components are modulated under increased stabilization demands. Methods Twenty healthy young adults (10 females, 10 males; age 20–35 years) performed treadmill walking at preferred speed under two conditions: tray-only and tray with water-filled cup. Participants carried the tray using either the dominant or non-dominant hand. Full-body kinematic data were collected using a markerless motion capture system (Theia3D). Principal Component Analysis (PCA) within the PMA framework was used to extract principal movement components (PMs), principal positions (PPs), and principal accelerations (PAs). Condition differences were assessed using paired-samples t-tests or Wilcoxon tests on PCA-derived movement variables. Results Carrying a water-filled cup during treadmill walking induced selective changes in multiple principal movement components (p < .05, several p < .001), with large effect sizes observed across several components. The overall low-dimensional gait structure remained preserved (no changes in PM1), suggesting stable locomotor control. Significant condition-dependent differences were observed in several PCA-derived movement components, suggesting task- related modulation of movement control. Visual inspection of higher-order PMs suggested condition-dependent down-regulation of those whole-body movement components which included significant motion of the tray-holding arm, whereas more variability was observed in task-irrelevant movement components. Discussion The findings demonstrate that object-stabilization demands during walking do not globally interfere with locomotor organization but instead induce selective reorganization of specific movement components. In line with Optimal Feedback Control Theory, the motor system appears to selectively adapt its coordinative movement patterns. Conclusion Carrying a water-filled cup during treadmill walking induces task-specific adaptations in movement coordination, characterized by selective reorganization of movement components. References Federolf, P., Reid, R., Gilgien, M., Haugen, P., & Smith, G. (2013). The application of principal component analysis to quantify technique in sports. Scandinavian Journal of Medicine & Science in Sports, 24(3), 491–499. https://doi.org/10.1111/j.1600- 0838.2012.01455.x Todorov, E., & Jordan, M. I. (2002). Optimal feedback control as a theory of motor coordination. Nature Neuroscience, 5(11), 1226–1235. https://doi.org/10.1038/nn963