Limits of Stability As a Constraint of the Virtual Whole-Body Motor Skill Learning in Parkinson’s Disease

BACKGROUND: Parkinson's disease (PD) can impair postural control and reduce functional limits of stability (LOS), which may constrain exploration and learning in whole-body motor tasks. AIM: This study investigated whether practicing whole-body virtual motor tasks changes LOS and whether LOS is associated with motor learning outcomes in adults with PD and age-matched healthy controls. METHODS: Twenty-five adults aged >= 50 years participated: 12 with PD and 13 healthy controls. Participants with PD were assessed in the medication ON state. Participants practiced four Kinect Adventures! games across 12 sessions. Game performance was assessed at pre-test, post-test, and one-month retention. LOS was assessed at pre-test and post-test using a center-of-pressure targeting task. LOS changes were examined with a mixed repeated-measures ANOVA. Structural equation modeling tested whether baseline LOS and practice-related individual variability in LOS (Delta LOS) predicted retained in-game scores. RESULTS: The Group & times; Moment interaction for LOS was significant, but Bonferroni-adjusted post hoc comparisons did not identify significant pairwise differences. There were no main effects of Group or Moment. Baseline LOS did not significantly predict retention performance. In contrast, Delta LOS significantly predicted retention performance, explaining 15.4% of the variance in the latent retention outcome. INTERPRETATION: Whole-body virtual task practice did not produce a uniform group-level increase in LOS. However, Delta LOS significantly predicts retention performance, suggesting that individual variability during acquisition is associated with long-term motor learning outcomes in adults with PD and healthy older adults.