PhD student, National University of Singapore / Advanced Robotic Centre Singapore
Development of a novel over-ground walking device for gait rehabilitation in older stroke survivors
With growing numbers of stroke survivors, walking assistive robots have recently received much attention. In our research, we propose an effective robotic walker system to support the biological gait pattern of neurologically challenged individuals for the practical daily use. This system consists on an omni-directional mobile platform as well as an active body weight support (BWS) unit to facilitate active pelvic motions, which simplifies the mechanical structure by eliminating additional actuators. The user interacts with the system through a six DOF force/torque sensor and an admittance controller which enables a natural and intuitive interface. In this way, the system can provide stability, balance, and gait training. It can also provide perturbation, resistance, and error augmentation training methods to enhance training efficacy. A set of wearable sensors (IMU and EMG) are used to provide quantitative measures of gait recovery and to monitor muscle condition and activation pattern. Current research involves integrating functional electrical stimulation module into the system to provide simulations for patients with severe drop foot to enhance gait recovery.
Preliminary tests in both healthy and stroke survivors have shown that the device perform adequately and present no hazard to the user [1-2]. Ongoing research will clinically validate rehabilitation protocols for this system based on principles of motor learning and neuroplasticity in 100 older chronic stroke patients. For this, a prospective single blind randomized control trial will be performed to compare conventional gait training vs. gait rehabilitation with the new walker. Our hypothesis is that a) the most effective gait training can only be achieved in the most natural setting which elicit proper sensory input and feedback closest to actual walking: the over-ground, and b) applying the motor learning principles such as error augmentation and motion adaptation will enhance the functional outcome.
 Y. Jing, F. A. Reyes and H. Yu. A Novel Robotic Walker for Over-Ground Gait Rehabilitation; Converging Clinical and Engineering Research on Neurorehabilitation II Biosystems & Biorobotics, pp. 1223-227, 2016.  F. Anaya Reyes, R. M. Kyung, H. Yu and V. Pasqui;Détermination d’un indice du risque imminent de chute pour la compensation active des instabilités posturales avec un robot d’assistance à la marche; Neurophysiologie Clinique/Clinical
Abstract: Restriction of pelvic lateral and rotational motions caused by robotic gait assistive devices can hinder satisfactory functional outcomes as it alters normal gait patterns. However, the effect of pelvic motion restriction caused by assistive devices on human locomotion is still unclear; thus, we empirically evaluated the influences of pelvic lateral and rotational motions on gait during over-ground walking by inhibiting the respective pelvic motions. The pelvic motions were restricted through a newly developed over-ground walking device. Variations in gait descriptive parameters as well as joint kinematics and muscle activation patterns were measured to indicate gait difference caused by pelvic restrictions. The results showed that pelvic lateral and rotational restriction significantly reduced the stride and step length as well as gait velocity and increased ratio of stance phase. It was also observed that the restriction caused a significant reduction in the range of motion of the ankle, knee, and hip joints. In addition, significantly higher muscle activations and prolonged patterns were observed in the tibialis anterior, gastrocnemius, and biceps femoris muscles, as compared to the normal patterns when the pelvis was restricted. We concluded that the pelvic restriction significantly altered normal gait dynamics, thus inhibiting the efficacy of gait rehabilitation.
Pub.: 03 Feb '16, Pinned: 30 Aug '17
Abstract: Body weight support (BWS) promotes better functional outcomes for neurologically challenged patients. Despite the established effectiveness of BWS in gait rehabilitation, the findings on biomechanical effects of BWS training still remain contradictory. Therefore, the aim of this study is to comprehensively investigate the effects of BWS. Using a newly developed robotic walker which can facilitate pelvic motions with an active BWS unit, we compared gait parameters of ten healthy subjects during a 10-m walk with incremental levels of body weight unloading, ranging from 0 to 40 % at 10 % intervals. Significant changes in joint angles and gait temporospatial parameters were observed. In addition, the results of an EMG signal study showed that the intensity of muscle activation was significantly reduced with increasing BWS levels. The reduction was found at the ankle, knee, and hip joints in the sagittal plane as well as at the hip joint in the frontal plane. The results of this study provide an important indication of increased lateral body balance and greater stabilization in sagittal and frontal plane during gait. Our findings provide a better understanding of the biomechanical effects of BWS during gait, which will help guide the gait rehabilitation strategies.
Pub.: 20 May '16, Pinned: 30 Aug '17
Abstract: Strength training is an aspect of gait rehabilitation, which complements balance control and weight-bearing training. However, conventional strength training does not show positive gait outcomes, due to lack of task specificity. Therefore, the aims of this study were to investigate the effects of a resistance force applied at the center of mass (CoM) and to investigate whether this exercise can be used for effective task-specific gait training. Using a novel robotic walker, a consistent resistive force was applied to the CoM of subjects in the posterior direction. Eleven healthy subjects were instructed to walk under five walking conditions with increasing forces, based on each subject's body weight (BW), at 0, 2.5, 5, 7.5, and 10% BW. Joint kinematics and mean amplitude and frequency of electromyography signals from nine major muscles were measured. The application of resistance resulted in significantly increased flexion angles at ankle, knee, and hip joints. A large amount of motor unit activation with lower firing rates was found at knee and hip joints, indicating that this type of resistance training can improve muscular strength and endurance in a task-specific manner. The long-term effects of the resistance training on neurologically challenged patients will be investigated in the future.
Pub.: 23 Mar '17, Pinned: 30 Aug '17
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