Changes in FDB and soleus muscle activity after a train of stimuli during upright stance

Brazilian Journal of Physical Therapy

Liria A. Okai¹  André F. Kohn¹ 

关键词: physical therapy;    posture;    foot;    human;    electromyography;    motor activity;    fisioterapia;    postura;    pé;    humano;    eletromiografia;    atividade motora;   

DOI  :  10.1590/S1413-35552012005000024

来源: SciELO

【 摘 要 】

BACKGROUND: Evidence of self-sustained muscle activation following a brief electrical stimulation has been reported in the literature for certain muscles. OBJECTIVES: This report shows that the foot muscle (Flexor Digitorum Brevis - FDB) shows a self-sustained increase in muscle activity during upright stance in some subjects following a train of stimuli to the tibial nerve. METHODS: Healthy subjects were requested to stand upright and surface EMG electrodes were placed on the FDB, Soleus and Tibialis Anterior muscles. After background muscle activity (BGA) acquisition, a 50 Hz train of stimuli was applied to the tibial nerve at the popliteal fossa. The root mean square values (RMS) of the BGA and the post-stimulus muscle activation were computed. RESULTS: There was a 13.8% average increase in the FDB muscle EMG amplitude with respect to BGA after the stimulation was turned off. The corresponding post-stimulus Soleus EMG activity decreased by an average of 9.2%. We hypothesize that the sustained contraction observed in the FDB following stimulus may be evidence of persistent inward currents (PIC) generated in FDB spinal motoneurons. The post-stimulus decrease in soleus activity may have occurred due to the action of inhibitory interneurons caused by the PICs, which were triggered by the stimulus train. CONCLUSIONS: These sustained post-stimulation changes in postural muscle activity, found in different levels in different subjects, may be part of a set of possible responses that contribute to overall postural control.

【 授权许可】

CC BY   
 All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License