Determine the true phase-space dimensionality of human gait

Determine the true dimensionality of the phase space governing human gait, including whether the four-dimensional two-link pendulum representation based on hip and knee angles and angular velocities is sufficient.

Background

The paper models gait biomechanics with a four-dimensional stochastic state consisting of the hip and knee angles and their angular velocities. It explicitly notes that, unlike the mechanical two-link pendulum, the actual dimensionality of human gait is not known in advance. The authors suggest examining the autocorrelation of residual noise after drift estimation to assess whether additional state variables or more general integro-differential or time-delay descriptions are required. Thus, establishing the true dimensionality remains an unresolved modeling issue underlying the validity of the proposed four-dimensional Fokker–Planck formulation.