Anticipatory postural adjustments in arm muscles associated with movements of the contralateral limb and their possible role in interlimb coordination |
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Authors: | Fausto Baldissera Viviana Rota Roberto Esposti |
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Institution: | (1) Istituto di Fisiologia Umana II dell’Università degli Studi di Milano, Via Mangiagalli 32, 20133 Milano, Italy |
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Abstract: | While sitting on a turnable stool, with both shoulders flexed at 90° or, alternatively, with arms parallel to the trunk and
the elbows flexed at 90°—the hands being semisupine—subjects performed unidirectional and cyclic movements on the horizontal
plane of the right arm (adduction–abduction) or hand (flexion–extension). The left arm was still, in a position symmetrical
to that of the right limb and with the hand contacting a fixed support by the palmar or dorsal surface. During both unidirectional
and cyclic arm or hand movements, activation of the prime mover muscles (right Pectoralis Major for arm adduction and Infraspinatus for abduction; right Flexor Carpi Radialis and Extensor Carpi Radialis for the hand movements) was accompanied by activation of the homologous muscles of the contralateral arm and inhibition of
antagonists. The contralateral activities (1) regularly preceded the burst in the movement prime movers and (2) were organised
in fixation chains that, exerting forces on the hand fixed support, will counterbalance the rotatory action exerted on the
trunk by the primary movement. Based on these features, these activities may be classified as anticipatory postural adjustments
(APAs). The observed APAs distribution is such as to favour the preferential (mirror symmetrical) coupling of upper limb movements
on the horizontal plane. The possible role of these APAs in determining the different constraints experienced when performing
mirror symmetrical versus isodirectional coupling is discussed. |
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Keywords: | Posture APAs Voluntary movement Movements coupling Upper limbs Human |
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