Résumé
The generation and execution of anticipatory postural adjustments (APAs) depend on the complex distributed neural networks, involving cerebral cortex (including premotor cortex and primary motor area), thalamus, basal ganglia, cerebellum, and divided into stratified mode and parallel mode. The basal ganglia and premotor cortex contribute to code the motor planning of APAs. Supplementary motor area and pedunculopontine nucleus in the brainstem co-regulate the timing of APAs. Primary motor area projects cortical motor fibers to target area during the initiation of APAs. The pontomedullary reticular formation integrates and projects fibers to the spinal cord. The cerebellum is mainly related to the coordinated coupling of muscles during APAs.
Résumé
Objective To explore the effect of acute endurance exercise on the balance control,maximum contraction of the back extensor and the anticipatory postural adjustments(APAs) and compensatory postural adjustments (CPAs) of the lumbar vertebra.Methods Seventeen male students from a police college participated in this study voluntarily.Three tests were performed right before and after the 10000 meters run:the single foot standing test with eyes closed,maximum contraction test of the back extensor and arm-rising test.The maximum voluntary contraction (MVC) of the back extensor and the time of standing with eyes closed were collected.The sEMG activities of lumbar erector spinae(LES) and Lumbar multifidus(LMF) as lumbar stable muscles were recorded.The pre-activation time and integrated EMG of APAs and CPAs were calculated.Results Before and after the 10000 meters run,no significant difference was observed in MVC,but the time of single foot standing decreased significantly.On the condition of the internal postural perturbation,the LES was activated significantly earlier and the APAs IEMG of LMF decreased significantly after the run,but no significant difference was observed in the pre-activation time of LMF and APAs IEMG of LES.The CPAs IEMG of LES and LMF both decreased significantly after the run.Conclusions The acute endurance exercise of 10000 meters run does not cause fatigue of lumbar stable muscles,but it has an effect on the performance of body balance control.It has effects on the postural control strategies of the central nerve system in response to the internal sudden postural perturbation,resulting in the earlier pre-activation of LES to compensate the decreased activation magnitude of LMF.
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The anticipatory postural adjustments can be more precise in reflecting the ability of posture control,which associate with two kinds of neuromuscular model.Anticipatory postural adjustments disorders are found in stroke patients with hemiplegia,such as delay of muscle activation time,decrease of muscle activation,degradation of muscle recruitment order and reduction of adaptability.
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Performance of upper extremity function and movement sequence is influenced by postural control. Motor disorders lead to deficits in postural control, which subsequently may lead to postural instability of children with cerebral palsy (CWCP). This will limit their upper extremity activity performance. Management strategies help to support and enhance the CWCP’s upper extremity function so that they may engage with the activities of daily living. The purpose of this paper is to review previous literature on the influence of postural control towards upper extremity function. Literature searches were conducted in various electronic databases, including ProQuest, Science Direct, Springer Link, Sage, Wiley Online Library, and Google Scholar using specific key terms. Search terms included children with cerebral palsy; postural control; postural adjustments; upper extremity function; reaching and sitting and from references of retrieved articles. Nineteen journal articles published between 2000 and May 2015 were found. Most search results consisted of experimental studies, while others are reviews, case studies, and cross-sectional studies. Findings show that, postural control has a major influence on upper extremity function. In conclusion, it is necessary to highlight the importance of both factors to the CWCP parents or caregivers, as understanding and awareness on this matter is still inadequate in the community. Hence, a study is needed on the awareness of the postural control influence on upper extremity function among caregivers, as well as examining the implementation of management strategies in community settings.
Sujets)
Paralysie cérébraleRésumé
Indivíduos jovens pré-selecionam suas estratégias de ajuste postural antes que uma perturbação externa ocorra, com base nas características da tarefa. Entretanto, ainda não é bem conhecido de que maneira o sistema nervoso central lida com os ajustes posturais antecipatórios e compensatórios, mediante alguns treinos de equilíbrio que são comumente usados na prática clínica da Fisioterapia. Treze adultos jovens receberam 20 perturbações posturais externas de pegar uma bola arremessada pelo experimentador sobre condições de estabilidade e instabilidade postural (sobre uma espuma). As atividades eletromiográficas dos músculos tríceps braquial (músculo focal), retoabdominal e paravertebral lombar foram avaliadas nas janelas de tempo típicas dos ajustes posturais antecipatórios e compensatórios, assim como o pico do deslocamento do centro de pressão corporal após a perturbação. A magnitude das integrais da atividade eletromiográfica do músculo tríceps braquial foi significativamente menor em condição de instabilidade postural, não houve diferença estatística entre as condições para as integrais da atividade eletromiográfica dos músculos retoabdominal e paravertebral lombar. O pico do deslocamento anteroposterior do centro de pressão corporal foi similar entre as duas condições. Treino de equilíbrio associado à perturbação externa da postura sobre espuma pode não ser mais eficaz ou eficiente do que sobre uma superfície estável, quando se pretende alterar a atividade dos músculos posturais do tronco. Além disso, este tipo de intervenção pode corroborar para diminuir a ativação antecipatória (ajustes posturais antecipatórios) do músculo focal.
Young individuals preselect their postural adjustment strategies before an external perturbation, based on the characteristics of the task. However, it is not well documented how the central nervous system deals with anticipatory and compensatory postural adjustments during some balance training programs, which are commonly used in Physical Therapy settings. Thirteen young individuals were submitted to 20 external postural perturbations of catching a ball thrown by an experimenter in conditions of postural stability and instability (standing on a foam). The electromyographic activities of triceps brachii (focal muscle), rectus abdominis, and lumbar paraspinal muscles were investigated in the time windows typical for anticipatory and compensatory postural adjustments, as well as the center of body pressure peak displacement after the perturbation. The magnitude of the triceps brachii integral electromyographic activity was significantly smaller in conditions of postural instability, there was no statistical difference between the stable and unstable conditions for the integral electromyographic activity of the rectus abdominis, and lumbar paraspinal muscles. The peak of the center of body pressure anterior posterior displacement was similar between the two conditions. Balance training associated with external perturbation standing on a foam might not be more effective or efficient than when standing on a stable surface, when it seeks to modify the activity of the postural trunk muscles. In addition, this balance training may contribute to decrease the electromyographic activity (anticipatory postural adjustments) of the focal muscle.