METHOD AND DEVICE FOR ISOKINETIC
QUADRICEPS EXERCISE USING
PNEUMATIC MUSCLE ACTUATOR
(PMA) RESISTANCE: COMPARISON TO
FREE WEIGHT EXERCISE
M. COWGILL, C. PHILLIPS, D. REYNOLDS, J. SERRES,
K. HALL, S. MOHLER
Departments of Biomedical, Industrial, and Human
Factors Engineering, Wright State University,
Dayton, OH
ABSTRACT
•
INTRODUCTION: The history of muscle atrophy in microgravity environments is a well
documented and continuing issue for space travelers. The lack of weight and pressure
normally experienced due to gravity leads to reduction in both muscle mass and bone
density which can be difficult to recuperate once back on earth and can lead to serious
injury. The situation creates a need for a source of resistance that is not dependent on
gravity. Our previous laboratory research has looked at the theoretical application of
pneumatic muscle actuators (PMAs) in place of free weights working against a simulated
human operator. METHODS: An exercise apparatus was created from a commercially
available machine (Valor Fitness-the CC-4 Leg Machine). Modifications were made to extend
the base to support the added equipment which includes a rig for attaching the Festo brand
PMAs to both the base and the rod at the knee’s point of rotation. Additional
instrumentation included a load cell, string potentiometer, and rotational potentiometer all
of which are used for both feedback and control of the system in LabVIEW. 10 subjects then
participated in testing to compare two types of quadriceps exercise methods-one using free
weights, the other using PMAs as described. Each exercise was performed until the subject
fatigued and was only performed once. Sessions were spaced at least a week apart to avoid
any training effect. Subjects were evaluated comparing their isokinetic exercise trajectory to
the ideal trajectory using the root-mean-square-error (RMSE) method. RESULTS: The RMSE
of the subjects in the two different quadriceps exercise methods was less than 5%.
DISCUSSION: This work demonstrates that equivalent exercise performance occurs when
using PMAs as a resistive device as compared to free weights. This research is applicable to a
method from more effective resistance exercise in microgravity environments.
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INTRODUCTION
• Space travelers suffer severe muscle atrophy
and bone density loss due to lack of gravity
• Current forms of microgravity exercise do not
address lack of body weight effect on muscle
and bone
• Previous laboratory research focused on
pneumatic muscle actuators (PMAs)
theoretical application as a resistive device in
exercise
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INTRODUCTION Continued
• PMAs thought to be capable of producing
resistance independent of gravity for better
microgravity strength training
– Festo fluidic muscle used for research
– Applied to a conventional quadriceps exercise
– Used to replace free weights for resistance
– More adaptive with finer incrementing of
resistance
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Festo Fluidic Muscle
Contracted
Relaxed
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METHODS
• Modifications made to exercise apparatus
(Valor Fitness CC-4 Leg Machine) to
incorporate PMAs and sensors
• PMAs used in parallel to increase resistance
capability
• LabVIEW programs created to collect data and
control PMA performance with interface
created for subject’s visual feedback
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Exercise Apparatus
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PMAs and Instrumentation
PMAs
Rotational
Potentiometer
Load Cell
String
Potentiometer
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LabVIEW Interface
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METHODS Continued
• Subjects given isokinetic workout pattern to
follow with visual cues and performance
feedback on computer screen
• Subjects asked to perform exercise at 25% of
maximum strength with free weights to
determine interactions between the subject
and
– Exercise apparatus
– LabVIEW interface
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Visual Cues and Feedback-Example
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Isokinetic Profile
• One cycle of isokinetic workout profile
– 5 second hold with leg bent
– 5 second isokinetic motion to extended leg
– 5 second hold with leg extended
– 5 second isokinetic motion to bent leg
• Subject asked to repeat until fatigued (or
experienced pain) or tester concluded
workout
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RESULTS
• Subjects struggled to visually “match” their
workout profile with ideal profile
– Not able to achieve ideal profile under any
conditions due to physiological constraints
– Ideal profile gave visual cues that caused subjects
to complete segments of the workout profile too
quickly or too slowly
• Many subjects unable to achieve lowering of
leg in 5 seconds-probably due to visual cue
confusion
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Subject Performance
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DISCUSSION
• Subjects must be evaluated for not only
maximum strength but also range of motion
• LabVIEW interface must reflect each subject’s
range of motion for most accurate visual
feedback of performance rather than “optimal
theoretical performance”
• Subjects must work out at more than 25% of
maximum strength to fatigue in less than 30
cycles
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DISCUSSION
• Results of pilot will be applied to research
program for more robust and useable results
• With subject customized modifications, more
accurate isokinetic exercise can be performed
• This device and its corresponding isokinetic
exercise utilizing PMAs promises to provide a
more effective method of resistance exercise
in microgravity environments.
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Disclosure Information
84th Annual AsMA Scientific Meeting
Mandy Cowgill
I have no financial relationships to disclose.
I will not discuss off-label use and/or investigational
use in my presentation
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