Does the stimulus provoking a stepping reaction correlate with step characteristics and clinical measures of balance and mobility post-stroke?

Background: Retraining stepping reactions in people post-stroke is vital. However, the relationship between the stimulus and resulting stepping performance in people post-stroke is unknown. We explored relationships between stepping stimulus and stepping reactions initiated by either paretic or non-paretic legs of people post-stroke and controls. Relationships were examined in the context of clinical measures of balance.

Methods: Centre of mass dynamics were measured during self-initiated destabilizing leaning stimuli that required stepping reactions by paretic and non-paretic legs of people post-stroke (n = 10) and controls (n = 10) to recover balance. Step characteristics of the first two steps of stepping reactions were measured. Correlations were calculated between clinical measures of balance and mobility and the centre of mass and step characteristics.

Findings: Steps were shorter and slower with decreased centre of mass fore-aft and downward displacement and velocity when initiated by paretic and non-paretic legs compared with controls. However, increase in centre of mass displacement and velocity in the fore-aft and downward direction tended to be associated with a greater increase in step length and speed when stepping reactions were initiated by the paretic and non-paretic legs compared with controls. Time to step initiation in response to onset of falling stimulus did not differ between groups. Strong positive correlations were found between clinical balance and mobility scores and centre of mass and step dynamics in fore-aft and vertical directions.

Interpretation: These results support objective measurement of centre of mass to quantify the stimulus influencing step dynamics and stepping performance during retraining interventions following stroke.