Gait adaptability.

Our activities of daily living inherently involve interacting with the physical environment. This interaction involves both reactive (feedback) and proactive (feedforward) gait adaptations. Reactive adaptations involve responses to mechanical perturbations and occur, for instance, when we stumble over a doorstep or slip on an icy spot on the pavement. Examples of proactive adaptations in response to visual stimuli include stepping over an obstacle, targeting precise foot placements when walking on rough terrain, stepping up to the pavement, or making a turn for going around a corner. These adaptations have to be implemented in our steady-state gait pattern, thus posing a challenge to center-of-mass control and maintenance of forward progression. Yet, despite the apparent complexity of adaptive bipedal walking, we commonly do this with remarkable ease. This chapter will provide a comprehensive overview of the behavioral strategies and control mechanisms that we apply for executing these common, yet complex, gait adaptations. In addition, how we use visual information for guiding proactive gait adaptations and path selection will be discussed. Finally, cognitive involvement during gait adaptations will also be addressed.