Abstract
The authors modeled the center of gravity vertical projection (CGV) and the difference, CP - CGV, which, combined, constitute the center of pressure (CP) trajectory, as fractional Brownian motion in order to investigate their relative contributions and t heir spatiotemporal articulation. The results demonstrated that CGV and CP - CGV motions are both endowed in complementary tashion with strong stochastic and part-deterministic behaviors. In addition, if the temporal coordinates remain similar for all 3 trajectories by definition, the switch between the successive control mechanisms appears for shorter displacements for CP - CGV and CGV than for CP trajectories. Results deduced from both input (CG,) and muscular stiffness (CP - CGV) thus provide insight into the way the central nervous system regulates stance control and in particular how CG and CP - CG are controlled.