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

Abstract

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.

Interlimb Coordination During the Stance Phase of Gait in Subjects With Stroke

“…These findings support the argument for the dysfunction of the ventral-medial system over the ipsilesional limb, also hypothesised in other studies [30][31][32] , as one of the causes for impaired interlimb relation in stroke subjects. This hypothesis assumes special relevance considering that the stroke participants in this study present lesions in the internal capsule, which can be associated to dysfunction of the cortico-reticular pathway 63 , responsible for ipsilateral postural control.…”

“…This non-functional interlimb relation could be the result of excessive co-activation values of plantar flexor and dorsiflexor muscles of the ipsilesional limb 29 as a consequence of ipsilaterally mediated effects from the neurological lesion 30,43 and/or to an adaptation for poor stability during gait 37 .…”

“…Taking into account the changes observed in both contralesional 26,27 and ipsilesional 30 limbs during gait, a dysfunctional interlimb relation was hypothesised, compared to interlimb relation patterns observed in healthy subjects 9 . Specifically, a higher dysfunctional relation would be expected between the ipsilesional heel strike limb and the contralesional propulsion limb.…”

“…The major metabolic cost has been associated with the mechanical work done by the ipsilesional limb, mainly to lift the centre of mass 28 . However, in spite of often being described as a compensatory limb that adapts to changes in the paretic limb 29 , changes observed in the ipsilesional limb have also been attributed to a possible dysfunction of ipsilateral distributed pathways responsible for postural control [29][30][31][32][33] . This could help us to understand why stroke subjects present lower performance of the contralesional limb when cyclic and antiphase ankle movements are executed with both limbs 34,35 .…”

The role of the ipsilesional side in the rehabilitation of post-stroke subjects

“…Moreover, the study of these tasks must focus the subphases with higher postural control demand, i.e. the initial phase of sit-to-stand and standto-sit (Silva et al, 2012b;Silva et al, 2012c), middle stance (Silva et al, 2012d;, double support (Silva et al, 2015;Sousa et al, 2013a;Sousa et al, 2013b) and gait initiation (Sousa et al, 2015a(Sousa et al, , 2015b.…”