Gait strategy changes with walking speed to accommodate biomechanical constraints

Steady state human locomotion at level ground needs compensatory energy input against impulsive energy loss during heel strike. Ground push-off by the stance leg right before the onset of double support phase appeared to be four times energy efficient than the an active hip torque generation during the swing phase [1]. However, if there is biomechanical constraint applied to the maximum allowable ankle push-off, despite its cost effectiveness, the nervous system may need to employ active hip torque to compensate heel strike energy loss to maintain steady state walking, as similar to the postural strategy changes from ankle to hip strategy to accommodate biomechanical constraints in response to backward perturbation [2]. In this study, we hypothesized that the gait strategy changes from ankle strategy (that compensates heel strike energy loss mostly by the ankle joint push-off impulse) to hip strategy (that generates additional energy input using active hip joint torque during the swing phase) to accommodate biomechanical constraints at ankle joint torque.