Self-triggered assistive stimulus training improves step initiation in persons with Parkinson's disease.
BACKGROUND
Prior studies demonstrated that hesitation-prone persons with Parkinson's disease (PDs) acutely improve step initiation using a novel self-triggered stimulus that enhances lateral weight shift prior to step onset. PDs showed reduced anticipatory postural adjustment (APA) durations, earlier step onsets, and faster 1st step speed immediately following stimulus exposure.


OBJECTIVE
This study investigated the effects of long-term stimulus exposure.


METHODS
Two groups of hesitation-prone subjects with Parkinson's disease (PD) participated in a 6-week step-initiation training program involving one of two stimulus conditions: 1) Drop. The stance-side support surface was lowered quickly (1.5 cm); 2) Vibration. A short vibration (100 ms) was applied beneath the stance-side support surface. Stimuli were self-triggered by a 5% reduction in vertical force under the stance foot during the APA. Testing was at baseline, immediately post-training, and 6 weeks post-training. Measurements included timing and magnitude of ground reaction forces, and step speed and length.


RESULTS
Both groups improved their APA force modulation after training. Contrary to previous results, neither group showed reduced APA durations or earlier step onset times. The vibration group showed 55% increase in step speed and a 39% increase in step length which were retained 6 weeks post-training. The drop group showed no stepping-performance improvements.


CONCLUSIONS
The acute sensitivity to the quickness-enhancing effects of stimulus exposure demonstrated in previous studies was supplanted by improved force modulation following prolonged stimulus exposure. The results suggest a potential approach to reduce the severity of start hesitation in PDs, but further study is needed to understand the relationship between short- and long-term effects of stimulus exposure.
Department of Physical Therapy & Rehabilitation Science, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
Robert A
RA
Creath
Michelle
M
Prettyman
Lisa
L
Shulman
Marjorie
M
Hilliard
Katherine
K
Martinez
Colum D
CD
MacKinnon
Marie-Laure
ML
Mille
Tanya
T
Simuni
Jane
J
Zhang
Mark W
MW
Rogers
D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D003627:Data Interpretation, Statistical; D005081:Exercise Therapy / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D020233:Gait Disorders, Neurologic / Q000209:etiology / Q000534:rehabilitation*; D006801:Humans; D008124:Locomotion / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000150:complications / Q000534:rehabilitation*; D010812:Physical Stimulation; D011187:Posture / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D014732:Vibration