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Repetitive Stress: Improved EWAS Takes Aim at Worker Injuries
By Gary Goettling
New technology is helping position an old injury-prevention research
tool developed for the poultry industry at the cutting edge of in situ
biomechanical monitoring.
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Research Engineers Jonathan Holmes and Sergio Grullon test
the improved EWAS. The system uses biomechanical measurements
and position-tracking technology to assess the movements of workers
performing highly repetitive tasks such as poultry deboning.
Information from the system can be used to reduce disorders like
carpal tunnel syndrome.
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Nearly 10 years ago the Georgia Tech Research
Institute (GTRI), in association with Georgia Tech’s School
of Applied Physiology, created an Ergonomic Work Assessment System
(EWAS)
to track the positioning
and arm move-ments of workers as they deboned poultry. The project,
part of the Agricultural Technology Research Program, was intended
to identify and then avoid the factors leading to repetitive stress
injuries.
The improved EWAS developed this year, with support from the
poultry industry, provides a more accurate and detailed assessment
by taking
advantage of technology that wasn’t available in the ’90s,
namely position-tracking technology typically used to create computer
animation.
“It measures arm position in three dimensions,” says GTRI
Research Engineer Jonathan Holmes. “You strap the system onto
your arm and move your arm around, and you can watch it moving on a
screen beside
you.”
The EWAS arm strap contains sensors that measure forearm
and wrist orientation as well as upper arm and shoulder activity.
Separate modules
on the back provide a global reference for the position sensors.
Muscle response is monitored through electromyography, a technique
for determining
the level of electrical activity in muscles. Torque and grip force
on the knife are calculated through special sensors by a method developed
by Liberty Mutual Research Institute for Safety, which is teaming
up with the Georgia Tech design team for that part of the system development.
As
a worker wearing the arm strap cuts poultry, the aggregate data of
the back and arm position, muscle response, grip force, and torque
is transmitted wirelessly to a laptop computer allowing researchers
to study relationships among force, exertion, posture, and repetition.
The information can be used both to boost work efficiency on the
factory floor and to correct inefficient movements.
More importantly, EWAS
can help researchers assess the dynamics of muscle group interactions
in job rotation schemes designed to reduce
disorders such as carpal tunnel syndrome. This cumulative trauma
results when tendons in the wrist become inflamed due to repetitive
activity.
Symptoms include burning, tingling, or numbness in the fingers; discomfort
in the wrist, forearm, or upper arm; and difficulty in gripping.
“By monitoring these forces and positions, you can put numbers
to physical motions and get a good idea of what is good and what is
bad,” says
Holmes. “You can determine if they are using certain muscles
too much, or if they are bending their wrist too far – you can
draw a lot of conclusions from that data that will eventually help
us determine which risk factors appear to impact injuries.”
In
many industries, workers who are required to perform repetitive tasks
at a fast pace may be at risk for injury unless they take periodic
breaks or find ways to reduce the stress and repetition of the job.
EWAS can help identify when those breaks need to be scheduled and
improve the current job rotations.
EWAS analysis might reveal that a different knife handle shape or
blade reduces wrist movement or the force required to perform a task.
The
position or height required to perform a certain job might be changed,
or workers might be rotated more often from a difficult procedure.
Although
being developed and field tested for the poultry industry, EWAS is
applicable to a variety of tasks ranging from keyboard operation
to heavy manual work. The system’s portability and small size
means testing can be done in the workplace itself, which yields more
realistic and accurate information than testing in a lab setting.
The
group is also investigating the development of studies to monitor
the back. They plan to pursue development of training or physical devices
that can reduce back injuries resulting from back instability conditions.
Gary
Goettling is an Atlanta-based freelance science and technology writer.
This article was written for Georgia Tech’s Research
Horizons magazine.
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