Figure 1.

Entrainment of human walking to periodic ankle torque pulses. Panel (A) shows experimental observation of unimpaired subjects (Ahn and Hogan, 2012b). The phase difference between toe-off (initiation of swing) and the initiation of the perturbation pulse is plotted as a function of stride number. Panel (B) shows comparable data generated by a simple mathematical model for various initial phases of the perturbation pulse (Ahn and Hogan, 2012a). In both (A and B), regardless of initial phase, the perturbation pulses converged to phase-lock at the end of double stance, close to toe-off.