Adaptation to the Repeated Mediolateral Foot Placement Perturbations

INTRODUCTION To walk stably without falling, all steps should be placed in the appropriate position. Mediolateral (ML) foot placement control has been investigated through various perturbations. However, there is not enough research on adaptations to perturbations repeated at a specific phase of strides. Our study aims to determine the adaptations during repeated ML foot placement perturbations. METHODS This protocol was piloted with one healthy adult participant. The participant walked in the Computer Assisted Rehabilitation Environment (CAREN, Motek, Amsterdam, Netherlands) consisting of a treadmill mounted on a movable platform. D-flow software recognized gait phases using motion capture system and made 5 cm of ML platform translation right after every toe-off. There were five sections: normal walking (NW)1, lateral perturbations (LP), NW2, medial perturbations (MP), and NW3, 5 minutes each. RESULTS AND DISCUSSION In both LP and MP, the SW became wider. Widened SW gradually returned to normal SW in NW3, after MP. However, at the beginning of NW2 after LP, the SW suddenly shrank narrower than normal SW. This data is consistent with the alternative hypothesis that the push-off of the trailing foot was strengthened to adapt to the LP, causing narrow SW in NW2 in compensation. Differences in kinematic features between LP and MP to widen SW were observed. The positions of the leading and trailing feet were controlled differently. The ML position of the trailing foot related to the pelvis caused wider SW in LP, while the ML position of the leading foot from the pelvis caused wider SW