Ankle dynamic in stroke patients: agonist vs. antagonist muscle relations

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Introduction: Atypical ankle patterns of muscle activity during gait are commonly reported in patients with stroke. These findings can be due to changes between tibialis anterior (TA) and soleus (SOL) coactivation mechanisms. Objective: To compare the electromyographic activity (EMGa) of SOL and TA muscles and antagonist coactivation (C) level in the contralateral (CONTRA) and ipsilateral (IPSI) limbs to the side of the stroke lesion during stance phase of the gait cycle. Methods: Twelve subjects with a stroke episode participated in this study. The electromyographic signal of TA and SOL and ground reaction forces were acquired while subjects walked at their self-selected speed. Values of ground reaction forces were used to divide the stance phase of gait into initial contact, midstance and terminal stance. In each subphase the magnitude of TA and SOL was calculated as well as the level of the antagonist C. Results: Although no statistical differences were found, mean values of SOL EMGa were lower in the IPSI in all stance phases in relation to the CONTRA limb, and the opposite was observed in the TA EMGa. Moreover, higher mean levels of antagonist C were only found during initial contact sub-phase in CONTRA limb and in the other sub-phases in the IPSI limb. Besides, statistical differences were observed only during midstance. Conclusion: In stroke subjects the antagonist C level during midstance of gait my reflected the dysfunction of the neuronal system over the IPSI limb.