Electromyographic and biomechanical characteristics of segmental postural adjustments associated with voluntary wrist movements. Influence of an elbow support. 2001

E Chabran, and B Maton, and C Ribreau, and A Fourment
Laboratoire de Physiologie du Mouvement INSERM U483, Université Paris XI - Bât 441, 91405 Orsay Cedex, France. ethelle.chabran@lpm.u-psud.fr

This study re-investigates the characteristics of segmental postural adjustments associated with rapid mono-articular movements and analyses their dependence on initial postural conditions. Subjects performed rapid voluntary wrist flexions and extensions while maintaining their upper limb posture as stable as possible, with or without an elbow support. Surface electromyographic activity (EMG) was recorded from Flexor carpi ulnaris, Extensor carpi radialis, Biceps brachii, Triceps brachii and Deltoideus anterior. The kinematics of the three joints and kinetics in the support condition were also recorded. A planar mechanical model was used to determine the muscle torque required to keep the upper limb posture constant while performing wrist movements. All subjects showed anticipatory postural adjustments (APA) which, unlike those described for whole-body postural control, could not counteract in advance the perturbing inter-segmental forces created by the movement. Postural muscles were activated before the wrist movement with a chronology specific to the direction of the wrist movement. Some postural muscular activities anticipated that of the prime-movers in accordance with muscle torque, which had to be applied to the joints to keep the upper limb posture constant. These results reveal that the central nervous system (CNS) uses the same organization of the motor command for the control of both segmental and whole-body posture: APA and corrective postural adjustments (CPA), which are based on well-organized anticipatory postural muscle activities (APMA), except that APA can be non-efficient in segmental postural control. The presence or absence of an elbow support influenced the level of activation of postural muscle but not their chronology. This result suggests that the CNS uses a sequence of APMA: a postural muscle synergy which is predetermined as a function of the intended direction of the movements and modulates the gain towards certain muscles, in accordance with the gravitational effects, and supports reaction changes.

UI MeSH Term Description Entries
D008297 Male Males
D008954 Models, Biological Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment. Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D009068 Movement The act, process, or result of passing from one place or position to another. It differs from LOCOMOTION in that locomotion is restricted to the passing of the whole body from one place to another, while movement encompasses both locomotion but also a change of the position of the whole body or any of its parts. Movement may be used with reference to humans, vertebrate and invertebrate animals, and microorganisms. Differentiate also from MOTOR ACTIVITY, movement associated with behavior. Movements
D009119 Muscle Contraction A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments. Inotropism,Muscular Contraction,Contraction, Muscle,Contraction, Muscular,Contractions, Muscle,Contractions, Muscular,Inotropisms,Muscle Contractions,Muscular Contractions
D011187 Posture The position or physical attitude of the body. Postures
D011930 Reaction Time The time from the onset of a stimulus until a response is observed. Response Latency,Response Speed,Response Time,Latency, Response,Reaction Times,Response Latencies,Response Times,Speed, Response,Speeds, Response
D002490 Central Nervous System The main information-processing organs of the nervous system, consisting of the brain, spinal cord, and meninges. Cerebrospinal Axis,Axi, Cerebrospinal,Axis, Cerebrospinal,Central Nervous Systems,Cerebrospinal Axi,Nervous System, Central,Nervous Systems, Central,Systems, Central Nervous
D004550 Elbow Region of the body immediately surrounding and including the ELBOW JOINT.
D004576 Electromyography Recording of the changes in electric potential of muscle by means of surface or needle electrodes. Electromyogram,Surface Electromyography,Electromyograms,Electromyographies,Electromyographies, Surface,Electromyography, Surface,Surface Electromyographies
D005260 Female Females

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