Compensation of lateralized fatigue due to referent static positional signals in an ankle-matching task: A feedforward mechanism

The main objective of this study was to examine whether static and dynamic signals from a non-fatigued reference ankle can differently improve the movement accuracy of a fatigued ankle. To address this question, subjects performed an ankle-matching task in a control condition and in a condition of local fatigue induced in the right tibialis anterior, in two matching conditions. In a bilateral condition, the matching task was completed with the two ankles simultaneously. In a unilateral condition subjects had to match the exact target position with the left non-fatigued ankle first and then tried to match the target position with the right fatigued ankle. Results showed that the final accuracy of the right fatigued ankle was degraded when matched with both ankles simultaneously while, for the unilateral condition, the final accuracy remained constant whether the ankle was fatigued or not. In addition, the EMG activity of the right tibialis increased significantly in the acceleration portion of the ankle movement for the unilateral condition. These results suggest that the CNS was able to integrate the correct static positional signals originating from the left reference ankle, to improve the movement accuracy of the controlateral fatigued ankle. This compensation of lateralized fatigue is operated in a feedforward manner.