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E. S. Kruger, J. A. Hoopes , R. J. Cordial, and S. Li

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. Background. Motor Variability Bernstein “repetition without repetition”. Background. Motor Variability

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E. S. Kruger, J. A. Hoopes , R. J. Cordial, and S. Li

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  1. 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

  2. Background • Motor Variability • Bernstein “repetition without repetition”.

  3. Background • Motor Variability • Bernstein “repetition without repetition”. • Degrees of Freedom (DOF) • Number of independent elements in a system.

  4. Background • 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?

  5. Error Compensation • DOFs work together to accomplish a given task by compensating for errors made. • Utilizing motor variability and redundant DOFs. Introduction

  6. 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)? Introduction

  7. Apparatus • Procedures • Data Analysis Methods

  8. Apparatus • Procedures • Data Analysis Methods

  9. Apparatus • Procedures • Data Analysis Methods

  10. 13 young, healthy adults • 2 sessions, 2-3 days apart • Index finger fatigued • All four fingers fatigued Procedures

  11. Force (N) 3 6 9 Time (s)

  12. Force (N) 3 6 9 Time (s)

  13. Force (N) Ftot FI FM FR FL 3 6 9 Time (s) Ftot = FI+ FM+ FR+ FL

  14. Apparatus • Procedures • Data Analysis Methods

  15. Force signals from individual sensors to analyze force profiles. Data Analysis

  16. From force profiles: • ΣVarFi = sum of the variances of individual finger forces • VarFtot = variance of total force • Error Compensation Index (ECI) = ratio of ΣVarFi to VarFtot.

  17. Results

  18. Variance (A) and Error Compensation Index (B) averaged over entire force ramp and across all subjects.

  19. Average Error Compensation Index over the 1st, 2nd, and 3rdone-second segments of the ramp phase (seconds 4,5,6).

  20. Discussion

  21. 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. Summary

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