Matt Simkins

Kinematic Data Analysis for Post-Stroke Patients Following Bilateral Versus Unilateral Rehabilitation With an Upper Limb Wearable Robotic System

Robot-assisted stroke rehabilitation has become popular as one approach to helping patients recover function post-stroke. Robotic rehabilitation requires four important elements to match the robot to the patient: realistic biomechanical robotic elements, an assistive control scheme enabled through the human-robot interface, a task oriented rehabilitation program based on the principles of plasticity, and objective assessment tools to monitor change. This paper reports on a randomized clinical trial utilizing a complete robot-assisted rehabilitation system for the recovery of upper limb function in patients post-stroke. In this study, a seven degree-of-freedom (DOF) upper limb exoskeleton robot (UL-EXO7) is applied in a rehabilitation clinical trial for patients stable post-stroke (greater than six months). Patients had a Fugl-Meyer Score between 16-39, were mentally alert (19 on the VA Mini Mental Status Exam) and were between 27 and 70 years of age. Patients were randomly assigned to three groups: bilateral robotic training, unilateral robotic training, and usual care. This study is concerned with the changes in kinematics in the two robotic groups. Both patient groups played eight therapeutic video games over 12 sessions (90 min, two times a week). In each session, patients intensively played the different combination of video games that directly interacted with UL-EXO7 under the supervision of research assistant. At each session, all of the joint angle data was recorded for the evaluation of therapeutic effects. A new assessment metric is reported along with conventional metrics. The experimental result shows that both groups of patients showed consistent improvement with respect to the proposed and conventional metrics.

Upper Limb Joint Space Modeling of Stroke Induced Synergies Using Isolated and Voluntary Arm Perturbations

Among other diminished motor capabilities, survivors of a stroke often exhibit joint synergies. These synergies are stereotypically characterized by involuntary joint co-activation. With respect to the upper limbs, such synergies diminish coordination in reaching, pointing, and other daily tasks. The primary goal of this research is to model synergy and quantify it in a comprehensive and mathematically tractable form. A motion capture system was used to measure joint rotations from stroke survivors and control subjects. These data showed that joint synergies are nonunique and asymmetric. The model also provided a way to calculate joint combinations that result in maximum and minimum synergy. Beyond providing a more complete view of synergies, this approach could facilitate new ways to evaluate and treat stroke survivors. In particular, this approach may have applications in diagnostic and treatment algorithms for use in rehabilitation robots.

Rhythmic affects on stroke-induced joint synergies across a range of speeds.

Joint synergies are one among several diminished motor capabilities that are associated with stroke. These synergies are characterized by a stereotypical combination of involuntary joint coactivations. This research measured the synergistic rotations of the shoulder in response to voluntary rhythmic motion of the elbow across a range of speeds. The experimental protocol included a total of 22 subjects divided into two groups: (1) stroke survivors and (2) neurologically intact controls. Rhythmic motion in stroke survivors resulted in comparable synergies to discrete movement. It was found that hemiparetic subjects had greater synergy than neurologically intact individuals for all speeds. Synergy was quantified using a synergy ratio. This ratio uses elbow rotation as an input in the denominator and shoulder rotation as an output in the numerator. The amount of shoulder synergy varied with the subject’s level of impairment as measured by a modified Fugl-Meyer assessment. As rhythmic speeds increased, the synergy ratios became higher for stroke subjects. This effect was especially pronounced for subjects with higher impairment. The relationships between synergies that arise from rhythmic and discrete movements are also discussed. The results of this study may have implications for therapeutic interventions, robotic rehabilitation approaches, and for the design of orthotic devices. More generally, these results shed light on the role of central pattern generators in hemiparetic motion.

Stroke-induced synergistic phase shifting and its possible implications for recovery mechanisms

AbstractAmong other diminished motor capabilities, survivors of a stroke often exhibit pathological joint synergies. With respect to the upper limbs, these deficits diminish coordination in reaching, pointing, and daily task performance. Past research on pathological synergies suggests that the synergistic relationship between joints is different for flexion than in extension. One explanation for different flexion and extension synergies is that there exists a time difference between the joint being volitionally moved and the joint that moves in synergy. The goal of this research was to measure these synergistic time differences. The experiment included 11 hemiparetic subjects who performed rhythmic elbow motions at five different frequencies. A motion capture system was used to record the resulting shoulder synergies. Synergistic shoulder rotations were found to exhibit frequency-dependent phase lags (delays) and leads (advances) in the paretic arm. Furthermore, the synergistic leads and lags varied with frequency and were subject specific. We found that timing differences between joints in pathological movements are comparable to differences that were observed by other researchers for normal, able-bodied movement synergies. Moreover, the fact that pathological synergies were evident in rhythmic motion suggests that they are spinal in origin. A significant amount research exists relating to able-bodied spinal synergies. Thus, the supposition that pathological synergies are an expression of normal synergies would tie disabled movement into a larger body of work related to able-bodied synergies. The rehabilitation implications of this possible connection are discussed.

Upper limb bilateral symmetric training with robotic assistance and clinical outcomes for stroke: A pilot study

Purpose – The purpose of this paper is to evaluate the physiotherapeutic benefits of bilateral symmetric training (BST) for stroke survivors affected by hemiparesis. Design/methodology/approach – Other studies have investigated symmetric physiotherapy. A key difficulty in previous work is in maintaining mirror-imaged trajectories between the affected and less-affected limbs. This obstacle was overcome in this work by using a two-armed robotic exoskeleton to enforce symmetry. In total, 15 subjects, > 6 months post stroke were, randomly assigned to bilateral symmetric robotic training, unilateral robotic training, and standard physical therapy. Findings – After 12 training sessions (90 minutes/session), the bilateral training group had the greatest intensity of movement training. They also had the greatest improvement in range of motion at the shoulder. The unilateral training group showed the greatest reduction in spasticity. Research limitations/implications – The rationale for symmetric physiotherapy is ...

A physiologically based hypothesis for learning proprioception and in approximating inverse kinematics.

A long‐standing problem in muscle control is the “curse of dimensionality”. In part, this problem relates to the fact that coordinated movement is only achieved through the simultaneous contraction and extension of multitude muscles to specific lengths. Couched in robotics terms, the problem includes the determination of forward and inverse kinematics. Of the many neurophysiological discoveries in cortex is the existence of position gradients. Geometrically, position gradients are described by planes in Euclidean space whereby neuronal activity increases as the hand approaches locations that lie in a plane. This work demonstrates that position gradients, when coupled with known physiology in the spinal cord, allows for a way to approximate proprioception (forward kinematics) and to specify muscle lengths for goal‐directed postures (inverse kinematics). Moreover, position gradients provide a means to learn and adjust kinematics as animals learn to move and grow. This hypothesis is demonstrated using computer simulation of a human arm. Finally, experimental predictions are described that might confirm or falsify the hypothesis.

Unilateral and Bilateral Rehabilitation of the Upper Limb Following Stroke via an Exoskeleton

Recent studies reported positive effects of bilateral arm training on stroke rehabilitations. The development of novel robotic-based therapeutic interventions aims at recovery of the motor control system of the upper limb, in addition to the increase of the understanding of neurological mechanisms underlying the recovery of function post stroke. A dual-arm upper limb exoskeleton EXO-UL7 that is kinematically compatible with the human arm is developed to assist unilateral and bilateral training after stroke. Control algorithms are designed and implemented to improve the synergy of the human arm and the upper limb exoskeleton. Clinical studies on the robot-assisted bilateral rehabilitations show that both the unilateral and bilateral training have a positive effect on the recovery of the paretic arm. Bilateral training outperforms unilateral training by a significant improvement of motion range and movement velocities.

Kinematic Analysis of Virtual Reality Task Intensity Induced by a Rehabilitation Robotic System in Stroke Patients

Robotic systems provide a paradigm shift in maximizing neural plasticity as part of human motor control recovery following stroke. Such a system shifts the treatment from therapist dependent to patient dependent by its potential to increase the treatment dose and intensity, as long as the patient can tolerate it. The experimental protocol included 10 post stroke hemiparetic subjects in a chronic stage. Subjects were treated with an upper limb exoskeleton system (EXO-UL7) using a unilateral mode, and a bilateral mode. Seven virtual reality tasks were utilized in the protocol. A kinematic-based methodology was used to study the intensity of the virtual reality tasks in each one of the operational modes. The proposed method is well suited for early evaluation of a given virtual reality task, or movement assistance modality during the development process. Pilot study data were analyzed using the proposed methodology. This allowed for the identification of kinetic differences between the assistance modalities by assessing the intensity of the virtual reality tasks.Copyright