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![Page 1: Error compensation during finger force production after one and four-finger voluntarily fatiguing exercise. E. S. Kruger, J. A. Hoopes, R. J. Cordial,](https://reader036.fdocuments.net/reader036/viewer/2022062413/5a4d1b257f8b9ab059996d52/html5/thumbnails/1.jpg)
Error compensation during finger force
production after one and four-finger
voluntarily fatiguing exercise.
E. S. Kruger, J. A. Hoopes, R. J. Cordial, and S. Li
By Kelsey Christensen
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• Motor Variability• Bernstein “repetition without repetition”.
Background
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• Motor Variability• Bernstein “repetition without repetition”.
• Degrees of Freedom (DOF)• Number of independent elements in a
system.
Background
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• Motor Variability• Bernstein “repetition without repetition”.
• Degrees of Freedom (DOF)• Number of independent elements in a
system.
• DOF Problem/Problem of Motor Redundancy• How does the CNS select a particular
solution from the infinite number of solutions?
Background
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Introduction• Error Compensation• DOFs work together to accomplish a
given task by compensating for errors made.
• Utilizing motor variability and redundant DOFs.
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Introduction• Error Compensation• DOFs work together to accomplish a
given task by compensating for errors made.
• Utilizing motor variability and redundant DOFs.
• How is error compensation affected when parts of the motor system are impaired (number of DOFs is reduced)?
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Methods• Apparatus• Procedures• Data Analysis
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Methods• Apparatus• Procedures• Data Analysis
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Methods• Apparatus• Procedures• Data Analysis
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Procedures• 13 young, healthy adults• 2 sessions, 2-3 days apart• Index finger fatigued• All four fingers fatigued
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3 6 9
Force (N)
Time (s)
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3 6 9
Force (N)
Time (s)
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3 6 9
Force (N)
Time (s)
Ftot
FI
FM
FR
FL
Ftot = FI+ FM+ FR+ FL
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Methods• Apparatus• Procedures• Data Analysis
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Data Analysis• Force signals from individual sensors to
analyze force profiles.
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• ΣVarFi = sum of the variances of individual finger forces
• VarFtot = variance of total force• Error Compensation Index (ECI) = ratio of
ΣVarFi to VarFtot.
From force profiles:
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Results
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• Variance (A) and Error Compensation Index (B) averaged over entire force ramp and across all subjects.
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• Average Error Compensation Index over the 1st, 2nd, and 3rd one-second segments of the ramp phase (seconds 4,5,6).
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Discussion
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Summary• The CNS is able to utilize the abundant
DOFs to compensate for motor system impairments to maintain the desired performance.• Problem of Motor Redundancy is a GOOD
thing.• Principle of Abundance – but there is a
limit.