Disrupted Walking After Stroke

Stroke, Current Therapy, and Our Research

More than 4 million people in the United States suffer residual walking impairment due to stroke. Most are left unsatisfied with their ability to walk despite completing physical therapy. Our laboratory’s understanding of the coordination deficit caused by stroke and the shared control between seated and walking tasks suggests that the limited effectiveness of these current therapies is due to the failure of those therapies to correct the fundamental source of walking deviations. Our theory that stroke causes a specific regression to a primitive coordination suggests that the behaviors current therapy tries to remove are actually necessary to compensate for a coordination deficit if no other walking aid is used.

Miscoordination and Walking

Given our understanding of how seated foot force control relates to walking, the deviant foot force control observed in the hemi-paretic limb of individuals following stroke would disrupt walking in a predictable manner. In the sagittal plane, for example, anteriorly biased foot force would tend to tip the person over backwards if not compensated for with body behavior or an external stabilizing force.

Gait Deviations as Compensations for a Coordination Deficit

Many of the atypical behaviors observed in post-stroke walking can be explained as mechanically viable behavioral compensations for the predicted coordination deficit. For example, asymmetrical weight bearing reduces the time and magnitude of force from the paretic limb that would cause unwanted rotational acceleration. In another example, increased hip flexion can be used to re-align the body’s center of mass with a misdirected force (see figure).

Our theory of hemi-paretic miscoordination as a cause for walking impairment also explains why patients appear to improve while in a body weight-supported treadmill training environment. The harness in that set-up not only produces a vertical force on the patient, but it can also provide lateral and rotational stability. This removes the need for potentially energetically expensive compensations, explaining the acute improvements in kinematics observed while patients train. It also explains the lack of transfer to over-ground walking, as the miscoordination was not retrained, but rather masked, during therapy.

 

>Back to All Research