Fatigue-induced changes of impedance and performance in target tracking.

Full Abstract

Kinematic variability is caused, in part, by force fluctuations. It has been shown empirically and numerically that the effects of force fluctuations on kinematics can be suppressed by increasing joint impedance. Given that force variability increases with muscular fatigue, we hypothesized that joint impedance would increase with fatigue to retain a prescribed accuracy level. To test this hypothesis, subjects tracked a target by elbow flexion and extension both with fatigued and unfatigued elbow flexor and extensor muscles. Joint impedance was estimated from controlled perturbations to the elbow. Contrary to the hypothesis, elbow impedance decreased, whereas performance, expressed as the time-on-target, was unaffected by fatigue. Further analysis of the data revealed that subjects changed their control strategy with increasing fatigue. Although their overall kinematic variability increased, task performance was retained by staying closer to the center of the target when fatigued. In conclusion, the present study reveals a limitation of impedance modulation in the control of movement variability.

Author information

Author/s: Selen, L P J (LP); Beek, P J (PJ); van Dieën, J H (JH);

Affiliation: Institute for Fundamental and Clinical Human Movement Sciences, Faculty of Human Movement Sciences, VU University Amsterdam, Van der Boechorststraat 9, 1081 BT, Amsterdam, The Netherlands. Lpjs2(-atsign-)eng.cam.ac.uk

Journal and publication information

Publication Type: Journal Article

Journal: Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale (Exp Brain Res), published in Germany. (Language: eng)

Reference: 2007-Jul; vol 181 (issue 1) : pp 99-108

Dates: Created 2007/07/02; Completed 2008/05/15; Revised 2008/11/20;

PMID: 17342476, status: MEDLINE (last retrieved date: 2/18/2009)

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