Use of harmonic ratios to examine the effect of cueing strategies on gait stability in persons with Parkinson's disease.

OBJECTIVE: To determine if gait stability, as measured by harmonic ratios (HRs) derived from trunk accelerations, is improved during 3 amplitude-based cueing strategies (visual cues, lines on the floor 20% longer than preferred step length; verbal cues, experimenter saying "big step" every third; cognitive cues, participants think "big step") in people with Parkinson's disease.

DESIGN: Gait analysis with a triaxial accelerometer.

SETTING: University research laboratory.

PARTICIPANTS: A volunteer sample of persons with Parkinson's disease (N=7) (Hoehn and Yahr stages 2-3).

INTERVENTIONS: Not applicable

MAIN OUTCOME MEASURES: Gait stability was quantified by anterior-posterior (AP), vertical, and mediolateral (ML) HRs; higher ratios indicated improved gait stability. Spatiotemporal parameters assessed were walking speed, stride length, cadence, and the coefficient of variation for stride time.

RESULTS: Of the amplitude-based cues, verbal and cognitive resulted in the largest improvements in the AP HR (P=.018) with a trend in the vertical HR as well as the largest improvements in both stride length and velocity. None of the cues positively affected stability in the ML direction. Descriptively, all participants increased speed and stride length, but only those in Hoehn and Yahr stage 2 (not Hoehn and Yahr stage 3) showed improvements in HRs.

CONCLUSIONS: Cueing for "big steps" is effective for improving gait stability in the AP direction with modest improvements in the vertical direction, but it is not effective in the ML direction. These data support the use of trunk acceleration measures in assessing the efficacy of common therapeutic interventions.