Joint Moments Exhibited by Chronic Stroke Subjects While Walking with a Prescribed Physiological Gait Pattern

The Lokomat robotic orthosis is used for locomotion therapy because it is capable of moving a subject's legs through a normal, symmetric gait pattern during intensive, time-unlimited training sessions. With a motion tracking system to track limb segments, 6 degrees of freedom loadcells at the leg cuffs to measure robot-subject interaction forces, and an instrumented split-belt treadmill, the kinematics and kinetics of stroke subjects were calculated as they walked in the Lokomat robotic orthosis. While the kinematic patterns of the stroke subjects appear to be similar to the age matched controls, the joint torques produced by the stroke subjects differ between the affected and unaffected limb as well as from the control subjects. Interestingly, stroke subjects tend to exhibit the classic lower limb synergy of hip flexion, hip abduction, and knee extension despite their leg moving through a normal pattern. Our findings suggest that stroke subjects will demonstrate abnormal torque coupling in their legs during gait despite the fact that the kinematic movement is symmetrical and physiological. Future studies will investigate whether prolonged training in the Lokomat can help resolve these abnormal synergy patterns.