Movement smoothness during a functional mobility task in subjects with Parkinson's disease and freezing of gait - an analysis using inertial measurement units.

The study was cross-sectional and compared groups at one time, so it cannot show that freezing caused less smooth movement. Only 6 healthy controls were included, and the retrospective power for the main smoothness comparison was approximately 50%. There was no Parkinson's group without freezing of gait, so the study cannot separate the effect of Parkinson's from the effect of freezing. Freezing events were not confirmed by synchronized video, and only a few participants showed pronounced freezing during the TUG test. The freeze-detection method used here was not the best validated one for a waist-mounted sensor. The off-medication state was partly judged by the researchers, which can vary between participants. The TUG has few steps, which the authors note is not optimum for analyzing gait variability, and they used signal processing adjustments to handle this. Walking speed increased across trials, so TUG duration may be affected by learning, although SPARC did not change across trials.

Funding was provided by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior. The supplied text does not state other conflicts of interest.

Do not treat these SPARC values as a validated clinical test or assume they prove freezing of gait caused the reduced smoothness. The study had only six controls, a retrospective power of approximately 50%, no Parkinson's group without freezing, and no video confirmation of freezing episodes.