Clinical and Biomechanical Factors in the Sit-to-Stand Decline in Parkinson's Disease

Background: Patients with Parkinson's disease (PwPDs) experience a progressive decline in their sit-to-stand (STS) ability, including a prolonged STS time, rising failure, and seat-off failure. The clinical and biomechanical factors contributing to this decline are unclear. Objectives: We investigated clinical and biomechanical factors associated with the different stages of STS decline in PwPDs. Methods: This cross-sectional study included 23 healthy controls (HCs) plus 40 PwPDs who we categorized by STS ability: 18 successful STS (SS), 12 failure-to-rise (FR), and 10 failure-to-seat-off (FS). Clinical assessments included motor symptoms (Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale), balance (Mini-Balance Evaluation Systems Test), and lower-limb strength. Biomechanical parameters measured using force plates included repetitive movements, slope of first-peak loading, and amplitude and temporal parameters. We conducted group comparisons and determined the age-adjusted area under the receiver operating characteristic curve (AAUC) and Spearman's correlations with the STS time (P < 0.05). Results: In the SS group, prolonged STS time was significantly correlated with amplitude and temporal parameters (rs = −0.849 to 0.986), for example, first-peak feet loading and its slope, reflecting impaired weight shifting from the buttocks onto the soles. These parameters effectively differentiated FR from SS (AAUC = 0.778–0.884) and FS from FR (AAUC = 0.758–0.992). Lower-limb bradykinesia differentiated FR from SS (AAUC = 0.870). All balance-related measures also strongly distinguished FS from FR (AAUC = 0.817–0.925). Conclusions: These findings highlight that weight-shifting impairments, along with bradykinesia in the earlier stages and balance deficits in the later stages, play pivotal roles in the progressive STS decline in PwPDs. Interventions targeting weight shifting, as well as bradykinesia, and postural control, could potentially help mitigate this decline.