Effects of freezing of gait on vertical ground reaction force in Parkinson's disease.

Vertical ground reaction force (vGRF) is a main kinetic gait analysis explaining body weight loading patterns. The study primarily aimed to understand effects of Freezing of gait (FoG) on vGRF in Parkinson's disease (PD). A secondary analysis for a walking dataset including biomechanical analyses for 26 PD participants (13 with FoG) was performed. Considering the normal pattern of vGRF curve, peaks during early stance (F1) and late stance (F3), and slope in- during mid-stance (F2) were used to represent the change in kinetic forces. vGRF parameters were compared between FoG and non-FoG participants, and at off- and on-medication. FoG participants showed higher vGRFs during mid-stance F2 magnitude (p = 0.003), and weaker vertical propulsion; F3 magnitude (p < 0.001). This coincided with delayed weight acceptance; F1 timing (p = 0.019), and midstance peaks; F2 timing (p = 0.004). At off-medications, the F2 magnitude was significantly higher (p = 0.006), F3 magnitude lower (p = 0.001), and F1 time slower (p = 0.034) in FoG. At on-medication, F3 magnitude was still significantly lower (p = 0.017), and F2 time was slower (p = 0.037) in FoG. This study reveals that FoG significantly affects vGRF, particularly F3 magnitude during the push-off phase. Analyzing vGRF is crucial for understanding and managing FoG, allowing for more targeted interventions to improve FoG outcomes.