Development of a method to determine abnormal joint torque coupling patterns during walking in chronic hemiparetic stroke

Abnormal joint torque coupling between (sub)maximal isometric hip extension and hip adduction torques previously reported under isometric conditions might lead to instability during walking in chronic hemiparetic stroke. Since this coupling has not been evaluated during a dynamic task, the aim of this study was to develop a method to quantify joint torque coupling patterns during walking. We developed a method to modulate hip extension torques during walking and measure its effect on the generation of hip abduction/adduction torques. A motor placed behind a treadmill was attached to the pelvis of a study participant and a constant bias force was applied in either anterior or posterior direction during walking. Hip joint torques were compared for different bias torques. Preliminary results of two healthy participants and one individual with stroke indicate that hip joint torques during stance phase of walking can be modulated by applying forces in anteroposterior direction to the pelvis. Applying a force in the posterior direction led to larger hip extension torques and lower hip abduction torques compared to normal walking in all participants while opposite responses were observed when a force was applied in the anterior direction. Based on these preliminary findings, we conclude that applying a force in anteroposterior direction to the pelvis during walking can be used to manipulate joint torque couplings during walking. Future experiments are expected to provide new insight into the effect of abnormal joint torque coupling patterns on walking stability following hemiparetic stroke