The effect of subjective postural vertical on forward flexed posture in Parkinson's disease

We developed a novel method to measure the angle of subjective postural vertical (SPV) and showed that the SPV may be related to the exacerbation of the forward flexed posture. The present study prospectively tested the effects of the subjective postural vertical on the exacerbation of the forward flexion of trunk (FFT) through long-term observation of Parkinson's disease patients. Evaluation of the posture included measuring FFT, the angle of lateral flexion of trunk, and the angle at the position that the patient subjectively perceived as the vertical position at a stationary upright position immediately after standing up at the time of initial observation, 6 months later, and 1 year later. The SPV angles worsened significantly at 6 months and 1 year compared to the first measurements (9.3 ± 6.7° vs. 10.8 ± 8.2° and 10.6 ± 7.8°, P