Step initiation is preceded by a series of electrical and mechanical events that constitute what are commonly termed anticipatory postural adjustments (APAs). These APAs are highly predictable in persons without neuromuscular or musculoskeletal impairments and are known to be advantageously influenced with sural nerve stimulation. Anticipatory postural adjustments in the stroke survivor population have been rarely studied and are poorly understood. Furthermore, the influence of sural nerve cueing on step initiation in stroke survivors has not been explored. This study investigated step initiation APAs in stroke survivors (n=15) in a reaction time paradigm under two "go" cues: (1) sural nerve stimulation; (2) visual light onset. Subjects performed 30 steps with each leg given randomly assigned go cues. Four primary outcomes were assessed: (1) Loading forces; (2) COP excursions; (3) EMG activity in bilateral tibialis anterior and gluteus medius muscles; (4) Reaction times of loading forces, COP and EMG onsets. Sural cueing significantly increased vertical loading, COP and EMG reaction times across all conditions of the stepping trials. The sural cue also produced significantly faster vertical loading compared to a visual cue. The loading amount and speed, EMG activity and net COP displacement were significantly influenced by the stepping condition (paretic or non-paretic). The results of this study are the first to report the ability to improve both reaction times and various aspects of the APA with sural cueing in a stroke population. In that prolonged reaction times are believed to be a major predictor of falls and APAs are diminished in stroke survivors, these results encourage training studies for improving reaction times and APAs.
University of Minnesota Ph.D. dissertation.May 2015. Major: Rehabilitation Science. Advisor: Carl Kukulka. 1 computer file (PDF); x, 119 pages.
Effects of Cutaneous Cueing on Step Initiation Anticipatory Postural Adjustments in Stroke Survivors.
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