JN Journal of Applied Physiology
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
 QUICK SEARCH:   [advanced]


     


J Neurophysiol (September 19, 2007). doi:10.1152/jn.00742.2007
This Article
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
98/5/2633    most recent
00742.2007v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Wei, K.
Right arrow Articles by Sternad, D.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Wei, K.
Right arrow Articles by Sternad, D.
Submitted on July 4, 2007
Accepted on September 14, 2007

Passive Stability and Active Control in a Rhythmic Task

Kunlin Wei1, Tjeerd M.H. Dijkstra2, and Dagmar Sternad3*

1 Rehabilitation Institute of Chicago, Northwestern University, Chicago, Illinois, United States
2 Kinesiology, Pennsylvania State University, University Park, Pennsylvania, United States
3 Kinesiology and Integrative Biosciences, Pennsylvania State University, University Park, Pennsylvania, United States

* To whom correspondence should be addressed. E-mail: dxs48{at}psu.edu.

Rhythmically bouncing a ball with a racket is a task that affords passively stable solutions as demonstrated by stability analyses of a mathematical model of the task. Passive stability implies that no active control is needed as errors die out without requiring corrective actions. Empirical results from human performance demonstrated that actors indeed exploit this passive dynamics in steady state performance thereby reducing computational demands of the task. The present study investigated the response to perturbations of different magnitudes designed on the basis of the model's basin of attraction. Humans performed the task in a virtual reality set-up with a haptic interface. Relaxation times of the performance errors showed significantly faster returns than predicted from the purely passive model, indicative of active error corrections. Systematic adaptations in the racket trajectories were a monotonic function of the perturbation magnitudes indicating that active control was applied in proportion to the perturbation. These results did not indicate any sensitivity to the boundary of stability. Yet, the influence of passive dynamics was also seen: i) the pattern of relaxation times in the major performance variable ball height was consistent with qualitative predictions derived from the basin of attraction; ii) racket accelerations at contact were generally negative signaling use of passive stability. These findings suggest that the fast return back to steady state was assisted by passive properties of the task. It was concluded that actors used a blend of active and passive control for all sizes of perturbations.




This article has been cited by other articles:


Home page
J. Neurophysiol.Home page
K. Wei, T. M. H. Dijkstra, and D. Sternad
Stability and Variability: Indicators for Passive Stability and Active Control in a Rhythmic Task
J Neurophysiol, June 1, 2008; 99(6): 3027 - 3041.
[Abstract] [Full Text] [PDF]




HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
Visit Other APS Journals Online
Copyright © 2007 by the The American Physiological Society.