Stroke impairs the proactive control of dynamic balance during predictable treadmill accelerations

We maintain balance during gait using both proactive and reactive control strategies. Damage to the brain from a stroke impairs reactive balance, but little is known about how a stroke impacts proactive control during walking. Stroke-related impairments to proactive control could become targets for interventions designed to improve responses to predictable disturbances and reduce fall risk. Therefore, we determined whether proactive strategies during predictable treadmill accelerations differed between people post-stroke (n = 14) and people without stroke (n = 14). Both groups walked with accelerations at random (every one to five strides) and regular (every three strides) intervals. We quantified the effects of the perturbations as changes to the centre of mass (COM) speed and used mechanical leg work to quantify the proactive strategies to slow the COM. Participants without stroke reduced peak COM speed better than those with stroke when perturbations were regular (-0.016 m s^-1 versus +0.004 m s^-1; p = 0.007). They also reduced positive leg work more during the perturbation step than the group post-stroke (-5.7% versus +2.5%; p = 0.003). One implication of these findings is that people post-stroke may be more susceptible to falls during predictable gait disturbances, and future work should identify the underlying impairments that cause these deficits.