Visual control of step length during overground locomotion: Task-specific modulation of the locomotor synergy.

This study evaluated the dynamics of gait adaptations during overground locomotion. Step length of 20 Ss increased or decreased (by 50% or 30%) on visual cues given at several different times (3 or 2) in the step cycle while walking or running, respectively. Ground reaction forces and temporal data were analyzed for each of the 10 trials per condition. Results showed that both vertical and horizontal impulses are modulated. The cuing time affected the way Ss altered step length. For example, during late cuing Ss made changes during free flight phase. Both magnitude and duration of force were altered suggesting modulation of a higher order parameter, the impulse. Success rate was lower for later cuing times. It was also lower for shorter step length than longer one. This suggests that balance requirements constrain the adaptations that can be made. The study implies far greater on-line peripheral control of locomotion than suggested by a dominant central pattern generator control theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)