Nonlinear Dynamics Used to Study the Influence of Treadmill Speed and Incline on the Human Hip Stability

This study uses the tools of nonlinear dynamics and the maximum Lyapunov exponents (LEs) are estimated to measure quantify the human hip stability starting from the experimental data of both hips’ flexion-extension (fl-ext) angle and abduction-adduction (abd-add) angle of 6 healthy subjects (HS) and 5 patients (P) affected by the osteoarthritis of knee. HS performed 9 walking tests on treadmill (TM) with 3 speeds and 3 incline angles, while the patients performed 3 walking tests on plane TM, before surgery (BS) and two months after surgery (AS). Rosenstein-Kantz algorithm and TISEAN software are used to analyze the 336 collected time series with methods and tools of nonlinear dynamics.