Soleus coordination deficits observed during standing in subacute stroke patients versus controls

This observational study compared bilateral coordination of soleus motor units during standing in 14 individuals undergoing inpatient rehabilitation for subacute stroke against 16 age- and sex-matched controls. The study involved two measurement sessions separated by one week. The exposure was stroke, with the comparator being healthy controls. The primary outcome was not explicitly reported; secondary outcomes included Berg Balance Scale (BBS) score, center of pressure (COP) metrics, and measures of soleus activity coordination.

Main results showed individuals post-stroke improved their BBS score between visits, though COP displacement and speed remained greater than in controls. Soleus activity was tuned anteriorly in control and non-paretic limbs but tuned laterally in paretic limbs. Bilateral synchronization of soleus activity was reduced in the paretic limb compared to controls. The cross-correlation lag between limbs was greater in individuals post-stroke than in controls at visit 1 but decreased to control levels by visit 2 (P=0.008). This decrease in lag was strongly correlated with improvement in BBS score (R=-0.94, P<0.001).

Safety and tolerability were not reported. Key limitations include the small sample size, the observational design which precludes causal inference, and unclear generalizability beyond this specific inpatient rehabilitation setting. Funding and conflicts of interest were not reported.

For practice, this study describes a specific neuromuscular coordination deficit in the soleus during standing balance after stroke and its association with functional improvement. The findings are mechanistic and associative; they do not establish the clinical efficacy of any intervention targeting this coordination. Clinicians should interpret the results as describing one component of post-stroke balance impairment within a narrow patient population.