The extrapolated body center of mass predicts subsequent foot placement choice during dynamic single-leg landings

Single-leg landing is a dynamic whole-body movement in which foot placement must be adjusted online to maintain postural stability. However, it remains unclear whether the position of the body center of mass (CoM) or the extrapolated center of mass (XcoM), which accounts for CoM velocity, is more informative for predicting foot placement choice. This study aimed to determine whether the positions of the body CoM and XcoM at the time when possible landing targets were presented could predict subsequent foot placement choice during single-leg landing and which provided better predictive accuracy. Twenty-four healthy participants performed a novel target-choice single-leg landing task from a 20-cm-high box. After movement initiation, two target lines (left and right) spaced 10 cm apart appeared on the landing platform. Participants were instructed to choose and land on one of the targets. A total of 99 trials were conducted, including 54 choice trials. To investigate whether the body CoM and XcoM positions at target appearance predicted subsequent foot placement choice, a binary logistic regression analysis was performed individually for each participant. The model fit was evaluated using log-likelihood, which was averaged across participants and compared using a paired t-test. Both the body CoM and XcoM models predicted the left/right foot placement choice. The body XcoM model showed a significantly larger log-likelihood value than the body CoM model. These results suggest that the body CoM position and its velocity influence the foot placement choice during whole-body dynamic landing.