Dynamic postural stability during sit-to-walk transitions in Parkinson disease patients.

In an effort to further our understanding of postural control in Parkinson's disease, we biomechanically evaluated the sit to walk task and its component tasks, sit to stand (STS) and gait initiation (GI) in 12 healthy older adults and 12 persons with Parkinson's disease (PWP). Performance was evaluated utilizing motion capture and two force plates. The major finding of this study was the inability of the PWP to appropriately merge the sequential component tasks (STS and GI) during STW. The PWP rose to nearly full height and had a longer delay between seat-off and gait initiation (P = 0.003 and P < 0.001, respectively) during STW. Additionally, the PWP moved with slower velocities leading to shorter, slower steps and decreased separation of the center of mass and center of pressure. These observed motor sequencing disturbances may be due to a disease related disability or limitations in proprioception, movement speed, muscular strength, and reduced general mobility. (c) 2008 Movement Disorder Society.