6.1B “Natural” synergies provide the basis for equilibrium maintenance strategy during trunk movements in the sagittal plane in standing human

Abstract

The stability of upright posture was evaluated in nine young and nine elderly subjects by measuring the maximum voluntary excursion of the centre-of-foot pressure in the anteroposterior and mediolateral directions during maximal voluntary leaning. Normalized maximum voluntary excursion, lean path, and mean time to attain maximum voluntary excursion, as well as range of centre-of-foot pressure oscillations at maximum voluntary excursion showed age-related changes. The elderly had a significantly smaller maximum voluntary excursion than the young in the backward and left leans with a non-significant reduction in maximum voluntary excursion leaning forward and right. The elderly approached maximum voluntary excursion in a less controlled manner exhibiting greater variability in their lean paths, and had greater range of oscillations at their maximum voluntary excursion. The elderly also took a significantly longer time to reach maximum voluntary excursion in the forward-lean trials.