Chronology of upper limb anticipatory postural adjustments associated with voluntary wrist flexions and extensions in humans.
Six sitting healthy subjects were instructed to keep a constant upper limb posture while performing wrist flexions and extensions. Acceleration of the wrist, elbow and shoulder joints, and surface electromyograms (EMGs) of the upper limb's main flexors and extensors were studied. Results indicated the existence of anticipatory (APA) and corrective postural adjustments. The APAs were based on a reproducible directional chronology of postural muscle activations. As shown by a simple mechanical model, this chronology was in accordance with the muscular torque which should be applied to the joints to keep the upper limb posture constant. All these data indicate that APA are involved in segmental posture, where their general organization is similar to those of APA associated with whole-body movements. The use of constant directional postural synergies well agrees with a simplification of the motor control according to Bernstein's theory.
Laboratoire de Physiologie du mouvement, Université Paris XI, Orsay, France. ethelle.chabran@lpm.u-psud.fr
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Chabran
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Fourment
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Maton
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Ribreau
D001132:Arm / Q000502:physiology; D004551:Elbow Joint / Q000502:physiology; D004576:Electromyography; D006801:Humans; D009043:Motor Activity / Q000502:physiology; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation; D011187:Posture; D011597:Psychomotor Performance / Q000502:physiology*; D012782:Shoulder / Q000502:physiology; D014836:Volition / Q000502:physiology*; D014953:Wrist / Q000502:physiology*