Postural control in hemiparetic patients during walking

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The mechanism involved in rapidly terminating and turning during human gait were studied. Normal subjects and hemiparetic patients were asked to stop walking or to turn toward the instructed direction as soon as they felt an electrical stimulus to the superficial peroneal nerve. In the normal subjects, there was an additional activity of gluteus medius for rotating the trunk. This activity was closely related to the timing of the opposite foot strike, independent of the phase of the gait cycle when the stimulus was applied. When a cue to stop or turn was applied during certain phases of the gait cycle, the normal subjects had to use a short step for braking the forward momentum. But the hemiparetic patients could stop or turn without using a stepping strategy because of their slower gait speed as well as cane usage.Based on these results, foot pressure and kinematic analyses were performed to identify the strategies for motor control when normal subjects and hemiparetic patients walk while wearing ankle-foot orthoses (AFOs). Independent of the degree of ankle fixation, the center of foot pressures on the plantar surface (inside of AFO) in normal subjects almost linearly moved from heel region to toe in the sagittal plane. We found that the control of knee movement during the stance phase played a crucial role in the smooth weight shift during walking with an AFO.On the other hand, a backward shifting of the center of foot pressures during early stance phase was observed in some hemiparetic patients. It became larger when wearing a shoehorn AFO with a shorter upright. The trajectories of foot pressures in the sagittal plane that are evaluated by an insole sensor system seem to be useful for making sure of the effects of AFOs on dynamic aspects of human gait.