Effect of direction and step length on anticipatory postural adjustments in stepping

Abstract

[Purpose] This research investigated the influence of step length and step direction on the anticipatory postural adjustment (APA) associated with rapid stepping initiation. [Subjects and Methods] Twenty-one young adults initiated stepping with their preferred limb at a fast pace. Eight experimental conditions comprising combinations of 4 directions (straight ahead; 0, 30, 60 and 90°) and 2 step lengths (short, 20% of body height; and long, 40% of body height) were used. Temporal and kinetic variables during the APA phase (from the initiation of COP displacement to heel-off of the swing limb) of step were measured using a 3D motion capture system. [Results] During the APA phase, both peaks of lateral and posterior shifts of COP decreased from 0 to 90°. [Conclusion] This finding suggests that the APA generated the precise amount of force to initiate stepping in the appropriate direction for the intended step length.