Adaptive changes to compensatory stepping responses

This study investigated the adaptive changes in the compensatory stepping response that occur with repeated exposure to the same postural perturbation. Perturbations were applied as forward platform translations (which evoked backward stepping), and responses were characterized using videorecordings, surface EMG, and ground reaction forces. Testing of seven healthy young adults demonstrated that the first exposure to a novel perturbation tends to evoke a stereotypical compensatory stepping response that shows some distinct differences when compared to ‘volitional’ stepping. Although individual subjects varied, increasing practice and familiarity often led to: (1) reduction in the incidence of stepping, (2) reduction in the number and/or length of steps needed to regain stability, and (3) the introduction of an anticipatory postural adjustment that procedes the unloading of the swing leg. These adaptations highlight the need to maintain adequate levels of unpredictability during balance assessment, in order to evoke the compensatory behaviour that may be characteristic of responses occurring in the unpredictable circumstances of everyday life.