Motor adjustments during time-constrained sit-to-walk in people with Parkinson's disease

Introduction: Sit-to-walk (STW) is a sequential task and a merge of sit-to-stand (STS) and gait initiation that are impaired in people with Parkinson's disease (PD). Performing sequential task under time constraint (e.g., stand up and walk to answer an urgent call) might influence people with PD due to their deficits on internal regulation of continuous, rhythmic and fast movements. It is known the PD behavior during STS and gait initiation tasks are impaired, however, little is known regarding PD behavior on STW. Thus, the aim of this study was to assess the motor behavior of people with PD and healthy older adults during the STW task under time constraint. Methods: Fourteen people with idiopathic PD and 14 healthy older adults (OA) participated in this study. They performed the STW task under a time constraint. STW performance (STW total duration, duration of each of the 4 phases of the STW, and the drop in the center of mass (COM) momentum, identified as Fluidity Index - FI), kinematics and kinetics outcomes were assessed throughout the task. Results: The PD group showed increased STW total time and lower FI, longer seat-off (Phase 1) time and first step (Phase 4) when compared to the OA group. Furthermore, the PD group showed more motor impairments (kinematics and kinetics) than the OA group throughout the task from seat-off until heel-off. Also, people with PD exhibited larger mediolateral COM displacement in the standing phase (Phase 2) and greater ground reaction force (GRF) in Phases 1 and 3. Conclusions: We observed that people with PD exhibited more restrictions when compared with healthy older adults on their STW performance, COM and GRF parameters during the STW under time constraint. Some clinical impairments usually observed in people with PD might explain their STW performance such as, motor planning deficits, less automatic motor control and mediolateral balance impairments.