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The effect of posture on early reaching movements

Out, L. and van Soets, A. J. and Savelsbergh, G. J. P. and Hopkins, Brian (1998) The effect of posture on early reaching movements. Journal of Motor Behaviour, 30 (3). pp. 260-272. ISSN 0022-2895

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Infants of about 5 months of age who have just mastered the ability to reach succeed more frequently in contacting an object when they are seated upright than when they are supine or reclined. That effect of posture disappears in the subsequent months. Whether that effect can be attributed either to insufficient muscular strength or to insufficient control over the mechanically unstable arm was the subject of the present investigation. Kinematics and electromyography (EMG) of reaching movements of 8 sitting and supine infants at 12, 16, and 20 weeks of age were recorded. Maximum levels of shoulder torque as well as kinematic stability measures were similar in both postures. Coactivation levels and the frequency of on-off switching of muscles turned out to be higher in the sitting than in the supine posture. The authors suggest that the difference in reaching behavior resulted from the degree of error in the feedforward control signal that was allowed by the different postures rather than either insufficient muscular strength or insufficient control over the mechanically unstable arm.

Item Type: Article
Journal or Publication Title: Journal of Motor Behaviour
Subjects: B Philosophy. Psychology. Religion > BF Psychology
Departments: Faculty of Science and Technology > Psychology
ID Code: 18928
Deposited By: ep_ss_importer
Deposited On: 06 Nov 2008 13:41
Refereed?: Yes
Published?: Published
Last Modified: 30 Jul 2014 09:26
Identification Number:

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