Beyond En-Bloc Turning: Head-Pelvis Coordination Variability in 360° turns in people with Parkinson’s

People with Parkinson’s Disease (PD) and Freezing of Gait (FOG) reportedly turn using an ‘en-bloc’ strategy, where the head and pelvis rotate together, unlike the head-leading movement seen in healthy adults. However, previous research relies on discrete maximum separation angles in 180° walking turns, despite recommendations to use 360° on-the-spot turns to better induce FOG. Current reports in people with Parkinson’s also fail to capture the time-varying coordination of body segments as the turn unfolds. Our study aimed to investigate head-pelvis coordination across strides during 360° on-the-spot turns in people with PD and FOG (PD + FOG), PD without FOG (PD-FOG), and healthy controls (HC). Twelve PD + FOG, 14 PD-FOG (tested ON medication), and 17 HC completed the turns during which head and pelvis angles in the transverse plane were calculated across strides in the first, middle and final sections of the turn. Head-pelvis angular difference did not differ between groups. However, PD + FOG showed increased coordination variability compared to HC (4.93°, p = 0.005) and PD-FOG (3.47°, p = 0.047); an observation that was no longer apparent after adjusting for MDS-UPDRS motor scores (p = 0.249) and MiniBEST (p = 0.051). PD + FOG also took more steps than PD-FOG (3.94, p = 0.008) and HC (6.47, p < 0.001), even after adjusting for covariates (MDS-UPDRS: p = 0.037; MiniBEST: p = 0.003). These findings suggest that people with PD do not necessarily exhibit more en-bloc turning compared to healthy controls. While head-pelvis coordination variability is higher in people with PD + FOG, this does not seem to be linked to FOG pathology per se , but rather balance deficits associated with disease severity. Increased step count seems to be related to FOG, which could be interpreted as a factors that might provoke FOG, but also serve as a compensatory strategy to promote postural stability.