Speed dependence in motor coordination during stair descent in healthy young adults: insights from uncontrolled manifold analysis.

This study utilized uncontrolled manifold (UCM) analysis to investigate the covariation structure of segment angles involved in the mediolateral and vertical stabilization of the center of mass (COM) during stair descent at different speeds in healthy young adults. Twenty-nine individuals participated in this study. Spatiotemporal and kinematic data were collected during the stair descent task. The swing phase was divided into the first half and second half of swing phases, and UCM analysis was performed to determine the covariation structure of segment angles that stabilize the mediolateral and vertical COM. The results showed that during the first half of swing phase, variability stabilizing the vertical COM was enhanced. In the second half of swing phase, while variability stabilizing the mediolateral COM was enhanced, variability that destabilizes the vertical COM is also enhanced. In conclusion, the findings suggest that different motor strategies are adopted for COM stabilization depending on the phase and speed of stair descent. These results contribute to a better understanding of stair descent from the perspective of COM coordinates.