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

Motor Variability Bernstein “repetition without repetition”. Background

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

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

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)?

Methods Apparatus Procedures Data Analysis

Methods Apparatus Procedures Data Analysis

Methods Apparatus Procedures Data Analysis

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

3 6 9 Force (N) Time (s)

3 6 9 Force (N) Time (s)

3 6 9 Force (N) Time (s) F tot F I F M F R F L F tot = F I + F M + F R + F L

Methods Apparatus Procedures Data Analysis

Force signals from individual sensors to analyze 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. From force profiles:

Results

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

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

Discussion

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.