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Age-related differences in the accur...

Poston, Brach J.

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Age-related differences in the accuracy of goal-directed contractions .

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Age-related differences in the accuracy of goal-directed contractions ./
Author:	Poston, Brach J.
Description:	191 p.
Notes:	Adviser: Roger Enoka.
Contained By:	Dissertation Abstracts International67-10B.
Subject:	Biology, Neuroscience. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3239398
ISBN:	9780542942198

Age-related differences in the accuracy of goal-directed contractions .
Poston, Brach J.

Age-related differences in the accuracy of goal-directed contractions . - 191 p.

Adviser: Roger Enoka.

Thesis (Ph.D.)--University of Colorado at Boulder, 2006.

The physiological mechanisms that underlie movement accuracy vary with the details of the task, including the age of the individual performing the action. Old adults, for example, exhibit a reduced ability to perform accurate goal-directed movements compared with young adults. A recent model, which has been termed the minimum variance theory, predicts that the central nervous system preferentially selects less variable trajectories to maximize accuracy during goal-directed tasks. This dissertation examined the predicted relation between trajectory variability and accuracy during isometric contractions performed by young and old adults. This was accomplished by examining the effects of practice, speed, target force, hand (dominant, non-dominant), and muscle size on the ability of young and old adults to achieve a target force within a specified time. The first study compared the practice-induced adaptations in motor-output and agonist-antagonist electromyographic (EMG) activity that accompanied improvements in end-point accuracy and motor-output variability in young and old adults. The findings indicated that the muscle activation strategies used to improve end-point accuracy with practice differed for young and old adults. The second study examined the influence of force level and contraction speed on end-point accuracy and variability of goal-directed isometric contractions. The results indicated that variation in end-point error and end-point variance did not change systematically across target forces, especially for slow contractions. The third study assessed end-point accuracy during rapid, goal-directed isometric contractions performed by the left and right hands of young and old adults. The results indicated that old adults exhibited greater end-point error with the left hand compared with the right hand initially, but after sufficient practice there was no difference between hands. The fourth study examined the influence of muscle size and force-trajectory variability on the end-point accuracy of rapid, goal-directed isometric contractions. The results indicated that large and small muscles can achieve similar levels of end-point accuracy despite differences in force-trajectory variability. Taken together, these results indicate that the decline in the accuracy of isometric contractions exhibited by old adults is not due to greater trajectory variability, but rather is caused by variation in EMG activity across trials.

ISBN: 9780542942198Subjects--Topical Terms:

1017680
Biology, Neuroscience.

Age-related differences in the accuracy of goal-directed contractions .
LDR:03368nam 2200289 a 45 001 958505
005 20110704
008 110704s2006 eng d
020 $a 9780542942198
035 $a (UMI)AAI3239398
035 $a AAI3239398
040 $a UMI $c UMI
100 1 $a Poston, Brach J. $3 1281966
245 1 0 $a Age-related differences in the accuracy of goal-directed contractions .
300 $a 191 p.
500 $a Adviser: Roger Enoka.
500 $a Source: Dissertation Abstracts International, Volume: 67-10, Section: B, page: 5589.
502 $a Thesis (Ph.D.)--University of Colorado at Boulder, 2006.
520 $a The physiological mechanisms that underlie movement accuracy vary with the details of the task, including the age of the individual performing the action. Old adults, for example, exhibit a reduced ability to perform accurate goal-directed movements compared with young adults. A recent model, which has been termed the minimum variance theory, predicts that the central nervous system preferentially selects less variable trajectories to maximize accuracy during goal-directed tasks. This dissertation examined the predicted relation between trajectory variability and accuracy during isometric contractions performed by young and old adults. This was accomplished by examining the effects of practice, speed, target force, hand (dominant, non-dominant), and muscle size on the ability of young and old adults to achieve a target force within a specified time. The first study compared the practice-induced adaptations in motor-output and agonist-antagonist electromyographic (EMG) activity that accompanied improvements in end-point accuracy and motor-output variability in young and old adults. The findings indicated that the muscle activation strategies used to improve end-point accuracy with practice differed for young and old adults. The second study examined the influence of force level and contraction speed on end-point accuracy and variability of goal-directed isometric contractions. The results indicated that variation in end-point error and end-point variance did not change systematically across target forces, especially for slow contractions. The third study assessed end-point accuracy during rapid, goal-directed isometric contractions performed by the left and right hands of young and old adults. The results indicated that old adults exhibited greater end-point error with the left hand compared with the right hand initially, but after sufficient practice there was no difference between hands. The fourth study examined the influence of muscle size and force-trajectory variability on the end-point accuracy of rapid, goal-directed isometric contractions. The results indicated that large and small muscles can achieve similar levels of end-point accuracy despite differences in force-trajectory variability. Taken together, these results indicate that the decline in the accuracy of isometric contractions exhibited by old adults is not due to greater trajectory variability, but rather is caused by variation in EMG activity across trials.
590 $a School code: 0051.
650 4 $a Biology, Neuroscience. $3 1017680
650 4 $a Biology, Physiology. $3 1017816
650 4 $a Health Sciences, Recreation. $3 1018003
690 $a 0317
690 $a 0575
690 $a 0719
710 2 0 $a University of Colorado at Boulder. $3 1019435
773 0 $t Dissertation Abstracts International $g 67-10B.
790 $a 0051
790 1 0 $a Enoka, Roger, $e advisor
791 $a Ph.D.
792 $a 2006
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3239398