Document Detail

Adaptation of joint flexibility during a reach-to-grasp movement.
MedLine Citation:
PMID:  19799170     Owner:  NLM     Status:  MEDLINE    
In the presence of motor redundancy, recent studies have shown that goal equivalent configurations of the body segments might be used by the central nervous system (CNS) instead of stereotypical movement patterns. In particular, some authors have shown that the CNS might choose a subset of joint configurations (termed the uncontrolled manifold or UCM) such that variability (goal equivalent variance or GEV) in this subset does not affect the value of a particular performance variable while variability in the orthogonal subset ORT (non-goal equivalent variance or NGEV) does. This hypothesis has been used successfully to test whether specific performance variables such as endpoint trajectory or segment global orientation are stabilized by the CNS or to study the influence of constraints on the organization of the movement. Few studies have examined the redundancy problem when considering obstacle avoidance during a grasping task. Indeed, the majority of the works on this topic considers non redundant arm models or do not take into account the movement variability. In the present work, we sought to study the coordination of the trunk and the arm during a reaching task involving an obstacle and to test whether such a spatial constraint in extrinsic space may induce particular adaptations in term of joint flexibility when considering the shoulder, elbow, and wrist joint center positions. In this framework, the upper limb three-dimensional kinematics was recorded. From the calculated joint angles, the variability in joint space related to the three joint center positions was computed and decomposed into GEV and NGEV. In agreement with the UCM hypothesis, results showed higher values of GEV than NGEV for all the experimental conditions. The main finding of the study is that joints' synergy is strengthened for the stabilization of the elbow joint center position during the late phases of the movement. This strengthening seems to be due mainly to an increase of GEV. Therefore, our results suggest that an increase of joint flexibility may be a mechanism by which the CNS takes into account a spatial constraint in extrinsic space represented by an obstacle.
Julien Jacquier-Bret; Nasser Rezzoug; Philippe Gorce
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Motor control     Volume:  13     ISSN:  1087-1640     ISO Abbreviation:  Motor Control     Publication Date:  2009 Jul 
Date Detail:
Created Date:  2009-10-05     Completed Date:  2009-12-01     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9706297     Medline TA:  Motor Control     Country:  United States    
Other Details:
Languages:  eng     Pagination:  342-61     Citation Subset:  IM    
HandiBio, Université du Sud, Toulon, 83957 La Garde, France.
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MeSH Terms
Arm / physiology*
Elbow Joint / physiology*
Hand Strength / physiology
Motor Activity / physiology*
Posture / physiology
Range of Motion, Articular / physiology*
Shoulder Joint / physiology*
Task Performance and Analysis
Wrist Joint / physiology*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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