Rong Song

Assistive Control System Using Continuous Myoelectric Signal in Robot-Aided Arm Training for Patients After Stroke

In some stroke rehabilitation programs, robotic systems have been used to aid the patient to train. In this study, a myoelectrically controlled robotic system with 1 degree-of-freedom was developed to assist elbow training in a horizontal plane with intention involvement for people after stroke. The system could provide continuous assistance in extension torque, which was proportional to the amplitude of the subjects electromyographic (EMG) signal from the triceps, and could provide resistive torques during movement. This study investigated the systems effect on restoring the upper limb functions of eight subjects after chronic stroke in a twenty-session rehabilitation training program. In each session, there were 18 trials comprising different combinations of assistive and resistive torques and an evaluation trial. Each trial consisted of five cycles of repetitive elbow flexion and extension between 90deg and 0deg at a constant velocity of 10deg /s. With the assistive extension torque, subjects could reach a more extended position in the first session. After 20 sessions of training, there were statistically significant improvements in the modified Ashworth scale, Fugl-Meyer scale for shoulder and elbow, motor status scale, elbow extension range, muscle strength, and root mean square error between actual elbow angle and target angle. The results showed that the twenty-session training program improved upper limb functions.

A Comparison Between Electromyography-Driven Robot and Passive Motion Device on Wrist Rehabilitation for Chronic Stroke

Background. The effect of using robots to improve motor recovery has received increased attention, even though the most effective protocol remains a topic of study. Objective . The objective was to compare the training effects of treatments on the wrist joint of subjects with chronic stroke with an interactive rehabilitation robot and a robot with continuous passive motion. Methods. This study was a single-blinded randomized controlled trial with a 3-month follow-up. Twenty-seven hemiplegic subjects with chronic stroke were randomly assigned to receive 20-session wrist training with a continuous electromyography (EMG)-driven robot (interactive group, n = 15) and a passive motion device (passive group, n = 12), completed within 7 consecutive weeks. Training effects were evaluated with clinical scores by pretraining and posttraining tests (Fugl-Meyer Assessment [FMA] and Modified Ashworth Score [MAS]) and with session-by-session EMG parameters (EMG activation level and co-contraction index). Results. Significant improvements in FMA scores (shoulder/elbow and wrist/hand) were found in the interactive group (P < .05). Significant decreases in the MAS were observed in the wrist and elbow joints for the interactive group and in the wrist joint for the passive group (P < .05). These MAS changes were associated with the decrease in EMG activation level of the flexor carpi radialis and the biceps brachii for the interactive group (P < .05). The muscle coordination on wrist and elbow joints was improved in the interactive groups in the EMG co-contraction indexes across the training sessions (P < .05). Conclusions. The interactive treatment improved muscle coordination and reduced spasticity after the training for both the wrist and elbow joints, which persisted for 3 months. The passive mode training mainly reduced the spasticity in the wrist flexor.

Myoelectrically controlled wrist robot for stroke rehabilitation

BackgroundRobot-assisted rehabilitation is an advanced new technology in stroke rehabilitation to provide intensive training. Post-stroke motor recovery depends on active rehabilitation by voluntary participation of patient’s paretic motor system as early as possible in order to promote reorganization of brain. However, voluntary residual motor efforts to the affected limb have not been involved enough in most robot-assisted rehabilitation for patients after stroke. The objective of this study is to evaluate the feasibility of robot-assisted rehabilitation using myoelectric control on upper limb motor recovery.MethodsIn the present study, an exoskeleton-type rehabilitation robotic system was designed to provide voluntarily controlled assisted torque to the affected wrist. Voluntary intention was involved by using the residual surface electromyography (EMG) from flexor carpi radialis(FCR) and extensor carpi radialis (ECR)on the affected limb to control the mechanical assistance provided by the robotic system during wrist flexion and extension in a 20-session training. The system also applied constant resistant torque to the affected wrist during the training. Sixteen subjects after stroke had been recruited for evaluating the tracking performance and therapeutical effects of myoelectrically controlled robotic system.ResultsWith the myoelectrically-controlled assistive torque, stroke survivors could reach a larger range of motion with a significant decrease in the EMG signal from the agonist muscles. The stroke survivors could be trained in the unreached range with their voluntary residual EMG on the paretic side. After 20-session rehabilitation training, there was a non-significant increase in the range of motion and a significant decrease in the root mean square error (RMSE) between the actual wrist angle and target angle. Significant improvements also could be found in muscle strength and clinical scales.ConclusionsThese results indicate that robot-aided therapy with voluntary participation of patient’s paretic motor system using myoelectric control might have positive effect on upper limb motor recovery.

Complexity Analysis of EMG Signals for Patients After Stroke During Robot-Aided Rehabilitation Training Using Fuzzy Approximate Entropy

The paper presents a novel viewpoint to monitor the motor function improvement during a robot-aided rehabilitation training. Eight chronic poststroke subjects were recruited to attend the 20-session training, and in each session, subjects were asked to perform voluntary movements of elbow flexion and extension together with the robotic system. The robotic system was continuously controlled by the electromyographic (EMG) signal from the affected triceps. Fuzzy approximate entropy (fApEn) was applied to investigate the complexity of the EMG segment, and maximum voluntary contraction (MVC) during elbow flexion and extension was applied to reflect force generating capacity of the affected muscles. The results showed that the group mean fApEn of EMG signals from triceps and biceps increased significantly after the robot-aided rehabilitation training . There was also significant increase in maximum voluntary flexion and extension torques after the robot-aided rehabilitation training . There was significant correlation between fApEn of agonist and MVC , which implied that the increase of motorneuron number is one of factors that may explain the increase in muscle strength. These findings based on fApEn of the EMG signals expand the existing interpretation of training-induced function improvement in patients after stroke, and help us to understand the neurological change induced by the robot-aided rehabilitation training.

Characterization of Stroke- and Aging-Related Changes in the Complexity of EMG Signals During Tracking Tasks

To explore the stroke- and aging-induced neurological changes in paretic muscles from an entropy point of view, fuzzy approximate entropy (fApEn) was utilized to represent the complexity of EMG signals in elbow-tracking tasks. In the experiment, 11 patients after stroke and 20 healthy control subjects (10 young and 10 age-matched adults) were recruited and asked to perform elbow sinusoidal trajectory tracking tasks. During the tests, the elbow angle and electromyographic (EMG) signals of the biceps brachii and triceps brachii were recorded simultaneously. The results showed significant differences in fApEn values of both biceps and triceps EMG among four groups at six velocities (pxa0<xa00.01), with fApEn values in the following order: affected sides of stroke patientsxa0<xa0unaffected sides of stroke patientsxa0<xa0age-matched controlsxa0<xa0young controls. A possible mechanism underlying the smaller fApEn values in the affected sides in comparison with aged-matched controls and in the aged individuals in comparison with young controls might be the reduction in the number and firing rate of active motor units. This method and index provide evidence of neurological changes after stroke and aging by complexity analysis of the surface EMG signals. Further studies are needed to validate and facilitate the application in clinic.

The therapeutic effects of myoelectrically controlled robotic system for persons after stroke : a pilot study

In this study, a myoelectrically controlled robotic system with one degree of freedom was developed to assist elbow training in the horizontal plane for patients after stroke. The system could provide assistive extension torque which was proportional to the amplitude of the subjects processed and normalized electromyograhpic (EMG) signal from triceps. The system also provided different resistive torques during movement, which were based on the maximum isometric voluntary extension (MIVE) and flexion (MIVF) torques. A study investigated its effect after 20-session of training for four weeks on the functional improvement of the affected arm in 3 subjects after stroke. Outcome measurements on the muscle strength at the elbow joint showed that there were increases in the MIVE and MIVF torques of the affected arms of all the subjects after the four-week rehabilitation training. The subjects could also reach a more extended position without the assistance of the robotic system than that before the four-week training

Kinetic measurements of hand motor impairments after mild to moderate stroke using grip control tasks

BackgroundThe aim of this study is to investigate quantitative outcome measurements of hand motor performance for subjects after mild to moderate stroke using grip control tasks and characterize abnormal flexion synergy of upper extremities after stroke.MethodsA customized dynamometer with force sensors was used to measure grip force and calculate rotation torque during the sub-maximal grip control tasks. The paretic and nonpartic sides of eleven subjects after stroke and the dominant sides of ten healthy persons were tested. Their maximal voluntary grip force was measured and used to set sub-maximal grip control tasks at three different target force levels. Force control ability was characterized by the maximal grip force, mean force percentage, coefficient of variation (CV), target deviation ratio (TDR), and rotation torque ratio (RTR). The motor impairments of subjects after stroke were also evaluated using the Fugl-Meyer assessment for upper extremity (FMA-UE) and Wolf Motor Function Test (WMFT).ResultsMaximal grip force of the paretic side was significantly reduced as compared to the nonparetic side and the healthy group, while the difference of maximal grip force between the nonparetic side and the healthy group was not significant. TDR and RTR increased for all three groups with increasing target force level. There were significant differences of CV, TDR and RTR between the paretic side and the healthy group at all the force levels. CV, TDR and RTR showed significant negative correlations with FMA-UE and WMFT at 50% of maximum grip force.ConclusionsThis study designed a customized dynamometer together with an innovative measurement, RTR, to investigate the hand motor performance of subjects after mild to moderate stroke during force control tasks. And stroke-induced abnormal flexion synergy of wrist and finger muscles could be characterized by RTR. This study also identified a set of kinetic parameters which can be applied to quantitatively assess the hand motor function of subjects after mild to moderate stroke.

Myoelectrically Controlled Robotic System That Provide Voluntary Mechanical Help for Persons after Stroke

This study described the operation of the myoelectrically controlled robotic system designed to assist wrist movement in a horizontal plane for patients after stroke. Electromyographic (EMG) signals from flexor carpi radialis (FCR), extensor carpi radialis (ECR) detecting subjects intention are used to control the mechanical assistance from the robotic system either to assist wrist flexion and wrist extension. This study had recruited five subjects after stroke. The results revealed that the range of motion (ROM) in the five subjects increased with the assistance of the myoelectrically controlled robotic system. The amplitude of agonist EMG signal decreased with the increase of assistance, which might reflect less effort was needed for the subject to perform the movement. This study demonstrates that it is feasible to apply myoelectrically controlled robotic system to provide substantial external torque to the affected wrist joint for subjects after stroke. Its therapeutic effect will be further investigated during stroke rehabilitation.

Arm–eye coordination test to objectively quantify motor performance and muscles activation in persons after stroke undergoing robot-aided rehabilitation training: a pilot study

This study designed an arm–eye coordination test to investigate the effectiveness of the robot-aided rehabilitation for persons after stroke. Six chronic poststroke subjects were recruited to attend a 20-session robot-aided rehabilitation training of elbow joint. Before and after the training program, subjects were asked to perform voluntary movements of elbow flection and extension by following sinusoidal trajectories at different velocities with visual feedback on their joint positions. The elbow angle and the electromyographic signal of biceps and triceps as well as clinical scores were evaluated together with the parameters. Performance was objectively quantified by root mean square error (RMSE), root mean square jerk (RMSJ), range of motion (ROM), and co-contraction index (CI). After 20 sessions, RMSE and ROM improved significantly in both the affected and the unaffected side based on two-way ANOVA (Pxa0<xa00.05). There was significant lower RMSJ in the affected side at higher velocities (Pxa0<xa00.05). There was significant negative correlation between average RMSE with different tracking velocities and Fugl-Meyer shoulder–elbow score (Pxa0<xa00.05). There was also significant negative correlation between average RMSE and average ROM (Pxa0<xa00.05), and moderate nonsignificant negative correlation with RMSJ, and CI. The characterization of velocity-dependent deficiencies, monitoring of training-induced improvement, and the correlation between quantitative parameters and clinical scales could enable the exploration of effects of different types of treatment and design progress-based training method to accelerate the processes of recovery.

EMG and kinematic analysis of sensorimotor control for patients after stroke using cyclic voluntary movement with visual feedback.

BackgroundClinical scales are often used to evaluate upper-limb deficits. The objective of this study is to investigate the parameters during voluntary arm tracking at different velocities for evaluating motor control performance after stroke.MethodsEight hemiplegic chronic stroke subjects were recruited to perform voluntary movements of elbow flexion and extension by following sinusoidal trajectories from 30 deg to 90 deg at six velocities in the horizontal plane by completing 3, 6, 8, 12, 15, 18 flexion and extension cycles in 36 seconds in a single trial, and the peak velocities ranged from 15.7 to 94.2 deg/s. The actual elbow angle and the target position were displayed as real-time visual feedback. The angular displacement of the arm and electromyographic (EMG) signals of biceps and triceps were captured to evaluate the sensorimotor control of the affected and unaffected side.ResultsThe results showed significant differences in the root mean square error (RMSE), response delay (RD) and cocontraction index (CI) when the affected and unaffected sides were compared during the arm tracking experiment (P<0.05). RMSE decreased with the increase in the tracking velocities for the affected and unaffected sides. And CI and RD increased with the increase in the tracking velocities for both sides. There was significant correlation between average RMSE of the six velocities and Fugl-Meyer shoulder-elbow score for the eight poststroke subjects.ConclusionsThe method and parameters have potential for clinical use in quantitatively evaluating the sensorimotor deficiencies for patients after stroke about the accuracy of motion, response delay and cocontraction between muscle pairs.