Dependence of anticipatory postural adjustments for step initiation on task movement features: a study based on dynamometric and accelerometric data.

The present study investigates the dependence of anticipatory postural adjustments (APA) for step initiation on velocity and length of the first step, by means of both dynamometric data, acquired by a force platform, and accelerometric data, achieved by means of sensor nodes positioned on the lower legs and on the trunk. Results focus on antero-posterior center of pressure (CoP) displacement and antero-posterior accelerations. Peak of backward CoP excursion during APA, considered as magnitude of APA, was found to depend mostly on step velocity, and, in less amount, to step length. Accelerometers detected a reliable accelerometric pattern during APA, and stance leg backward acceleration before stepping presents a peak with a behavior very similar to peak of CoP in terms of dependence on velocity and step. The results allow deduction on the role of APA to control step initiation, and suggest possible promising applications of portable and low-cost accelerometric sensors, to monitor motor performance in several fields as rehabilitation, clinics and closed loop applications.