Development of KIINCE: A kinetic feedback-based robotic environment for study of neuromuscular coordination and rehabilitation of human standing and walking

Abstract

Introduction: The objective of this article is to introduce the robotic platform KIINCE and its emphasis on the potential of kinetic objectives for studying and training human walking and standing. The device is motivated by the need to characterize and train lower limb muscle coordination to address balance deficits in impaired walking and standing.

Methods: The device measures the forces between the user and his or her environment, particularly the force of the ground on the feet (F) that reflects lower limb joint torque coordination. In an environment that allows for exploration of the user's capabilities, various forms of real-time feedback guide neural training to produce F appropriate for remaining upright. Control of the foot plate motion is configurable and may be user driven or prescribed. Design choices are motivated from theory of motor control and learning as well as empirical observations of F during walking and standing.

Results: Preliminary studies of impaired individuals demonstrate the feasibility and potential utility of patient interaction with kinetic immersive interface for neuromuscular coordination enhancement.

Conclusion: Applications include study and rehabilitation of standing and walking after injury, amputation, and neurological insult, with an initial focus on stroke discussed here.

Keywords: Biofeedback; design requirements; evaluation; gait rehabilitation; neurorehabilitation; rehabilitation devices; robot-assisted rehabilitation; stroke rehabilitation.

Figure 1.

Robotic force plates support the standing or walking human who can receive visual feedback on the display or kinematic feedback from plate anterior–posterior motion. Forces applied to the human via the force plates, handrail, or harness (see Figure 4) are measured and incorporated into feedback.

Figure 2.

A harness prevents the feet from translating anterior-posteriorly with respect to the force plate but allows the natural heel and toe rise of walking. Each foot is coupled to a plate with three nylon straps. One attaches to a foot harness near the heel and to the plate anterior to the toes. The other pair of straps straddles the first and is attached to a foot near the toes and to the plate posterior to the heel.

Figure 3.

The primary kinetic features of walking are shared between an initial walking algorithm on KIINCE and overground walking. The vertical (a) and anterior-posterior (b) components of F for overground walking (thin line) and walking on KIINCE (thick line) are shown as the mean of multiple cycles for a representative nonimpaired individual.

Figure 4.

A slack safety harness arrests falls while a stability harness can restrict torso pitch and roll via four straps at the shoulder and hip levels (posterior attachment points shown as asterisks). The straps are length and compliance adjustable and instrumented to measure force.

Figure 5.

On KIINCE we observed three individuals with stroke that showed distinct coordination differences between their paretic and nonparetic legs while performing a task similar to walking. In the sagittal plane, the location of an intersection point (xi) of foot force lines of action was calculated after adjusting for foot rollover. The location of xi was lower and more anterior in the paretic leg (filled circles) compared to the nonparetic leg (open circles). The hip is located at the open square (0,1). CM: center of mass.

Figure 6.

Tasks to retrain control of foot force magnitude and direction were piloted in individuals affected by stroke. The first task (participant visual feedback shown in (a)) required standing participants to position their center of pressure (vertical line) within the target (box). A second task (participant visual feedback shown in (c)) required standing participants to direct their foot force (gray arrow) to match the target vector (white arrow). The recorded targets and performance variables (paretic limb CP target (b) and paretic limb F direction target (d)) show that the paretic limb was capable of adjusting both aspects of foot force toward a target. CP: center of pressure.