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Improving Stepping-over
Responses in the Elderly using Simulated Objects
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Summary
This project employs virtual reality techniques to improve the ability of
elderly individuals at high risk for falling to step over obstacles.
Purpose
The long term goal of this work is to construct and test a system for elderly
individuals at high risk for falling that employs techniques to monitor and
improve their stepping-over response time and trains them in more effective
movement strategies. This method is expected to be safer than conventional
training and more rapid and precise in the feedback it provides to the patient.
Methodology
Simulated obstacles of various heights and lengths will be presented to
subjects wearing a head mounted display as they walk on a treadmill. Foot
position will be monitored by a computer to detect collisions between the
virtual object and the users' feet. During trials, vibrotactile feedback will
be presented to the heel or toe of the foot involved in a collision.
Progress
In the past four months a laboratory setup has been developed. Subjects will
wear an overhead harness to prevent injury in the case of a fall during
treadmill walking. A color video camera will be trained on the subjects' legs
from the side. This real time image will be viewed by the subject wearing a
head mounted display. The computer will add virtual images of rectangular
objects of varying heights and lengths at the subjects' feet. The subject will
be instructed to step over the obstacles on each step. The computer will
capture the images and detect any intersection of the user's feet with the
virtual obstacles. A collision by the toe on the front edge of the object would
indicate that the subject has not lifted the foot high enough, while a
collision with the heel on the top of the object would indicate that the
subject has not stepped far enough. Foot switches determine which foot is off
the ground. The vibrotactile feedback would then be directed to the heel or toe
of the foot that caused the collision.
Preliminary Results
The pilot project work has led to the following conclusions:
The most successful technique involves displaying a
side-view of stepping on a treadmill while the viewer repeatedly negotiates
computer-generated obstacles.
When stepping over obstacles during overground
walking, young, healthy persons step over higher objects by increasing knee and
hip flexion. This same strategy is employed when stepping over
computer-generated obstacles displayed during treadmill walking.
When stepping over obstacles during overground
walking, young, health persons step over longer objects by increasing stride
length. This same strategy is employed when stepping over computer-generated
obstacles displayed during treadmill walking.
In a small group of elderly subjects, the proposed
training regimen showed a positive result in that subjects were better able to
negotiate an overground obstacle course after 3 training sessions. A
randomized, controlled study must be conducted to separate out the nonspecific
effects.
Future Plans
Future studies include studies on frail elderly individuals with a history of
falls to determine if this intervention can result in reduced frequency of
falls. In addition, we plan to further develop the system so that it can be
used in a wide variety of clinical settings and clinical populations.
Future work in this project area could include employing
simulation techniques with walking aids such as canes and crutches. Other
potential areas of research include the study of improvements in fitness and
gait through simulation of walking situations for ambulatory nursing home
patients and teaching environmental factors and modifications to avoid falls.
The system could provide an enjoyable and safe environment for general
exercise, a safe setting for "wanderers", or a simulated practice
session for wayfinding and familiarization of nursing home patients with their
facility.
Recent Publication
Jaffe, DL, Use of Virtual Reality Techniques to Train Elderly People to Step
over Obstacles, Proceedings of the 1998 CSUN Technolgy and Persons with
Disability Annual Conference, Los Angeles, CA, March 13, 1998.
Related Work
This work is a follow-on to the Pilot Project, Obstacle Avoidance Training with Computer Simulated
Environments.
- Investigators
- David A. Brown, PhD, PT
- David L. Jaffe, MS
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