Parkinson’s disease (PD) is a common neurological disorder caused by the progressive loss of dopaminergic and other subcortical neurons (Braak et al. 2004). PD patients often suffer from impaired motor skills (Jankovic 2008). Besides a flexed posture, tremor at rest, rigidity, akinesia (or bradykinesia) and postural instability, motor blocks are a common negative effect of PD. Motor blocks (freezing) most commonly affect the patients’ legs during walking and are generally referred to as freezing of gait (FOG). Clinical assessment of PD is largely based on subjective patient reports. The Hoehn and Yahr (H&Y) scale * is commonly used to describe symptoms of PD progress (Hoehn and Yahr 1967).