THE FORCE DRIVEN HARMONIC-OSCILLATOR MODEL ACCURATELY PREDICTS THE PREFERRED STRIDE FREQUENCY FOR BACKWARD WALKING

It has been established that when gait speed is freely selected, there is a strong natural tendency for a stride rate and length combination to be utilized that results in minimized metabolic cost. A possible m echanism for this self-optimizing behavior is that a biomechanically o ptimal movement pattern is adopted, which should reduce or minimize me tabolic cost. When the legs are modeled as pendular force driven harmo nic oscillators (FDHO) the stride frequency during freely selected gai t is predictable as the pendulum's resonant frequency - the state in w hich force inputs to maintain oscillations are minimal. Thus, resonanc e has been proposed as a mechanism responsible for gait optimization. To further examine the durability of this mechanism, the FDHO model wa s applied to predict stride rates during both free forward and backwar d walking for two separate test sessions. Stride measures were stable across sessions. Forward walking resulted in 25% greater stride length s than backward, however, stride rates were statistically equal. Also, the FDHO model successfully predicted the preferred stride rate for b oth backward and forward walking. The resulting invariance of the stri de frequency and adjustment of stride length were interpreted as offer ing additional support for the resonance mechanism. (C) 1998 Elsevier Science B.V.