Both anticipatory and compensatory postural adjustments are adapted while catching a ball in unstable standing posture.

The main objective of this study was to analyze the role of balance exercises on anticipatory (APA) and compensatory (CPA) postural adjustments in different conditions of postural stability. Sixteen subjects were required to catch a ball while standing on rigid floor, trampoline and foam cushion surfaces. Electromyographic activities (EMG) of postural muscles were analyzed during time windows typical for APAs and CPAs. Overall there were a reciprocal activation of the muscles around the ankle and co-activations between ventral and dorsal muscles of the thigh and trunk during the catching a ball task. Compared to the rigid floor, the tibialis anterior activation was greater during the trampoline condition (CPA: p = 0.006) and the soleus muscle inhibition was higher during foam cushion condition (APA: p = 0.001; CPA: p = 0.007). Thigh and trunk muscle activities were similar across the conditions. These results advance the knowledge in postural control during body perturbations standing on unstable surfaces.

Ajustes posturais antecipatórios e compensatórios ao pegar uma bola em condição de estabilidade e instabilidade postural / Anticipatory and compensatory postural adjustments during catching a ball in condition of postural instability and stability

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.