Evidence for improved muscle activation patterns after retraining of reaching movements with the MIME robotic system in subjects with post-stroke hemiparesis

Abstract

Previously, we reported that chronic stroke subjects had significant improvements in isometric strength, free reaching extent, and clinical evaluations of function after training in the mirror-image movement enabler (MIME) robotic device. Our primary goal in this analysis was to investigate the hypothesis that the robotic training promoted improved muscle activation patterns. To this end, we examined the interaction forces, kinematics, and electromyograms recorded during training of eight different movement patterns in active-constrained mode. In this mode, the robot constrained the reaching movements to be toward the target, and the movement velocity was proportional to the force produced along the trajectory. Thirteen chronic stroke subjects trained in MIME for 24 1-h sessions over an eight-week period. Work output was significantly increased by week five in all eight movement patterns. Low-level subjects increased their extent of reach, while high-level subjects increased their speed. Directional errors in force production were reduced in six of eight movement patterns. Electromyographic data provided evidence for improved muscle activation patterns in the four movement patterns that started at tabletop level and ended at shoulder level. In contrast, there was no evidence of improved muscle activation patterns in any of the tabletop movements, with increased activation of antagonists in two movement patterns. This dichotomy may have been related to compensation at the shoulder girdle during movements that remained at tabletop level. A simple biomechanical model will be introduced to demonstrate the likelihood of this possibility.

Robot-assisted upper-limb therapy in acute rehabilitation setting following stroke: Department of Veterans Affairs multisite clinical trial

“…Sessions began with practice of targeted, twodimensional reaching movements at table level and then progressed to more complex, three-dimensional, out-ofsynergy movements beginning at table level and ending at eye level. Movement patterns incorporated into the training sessions have been previously described [6]. Representative beginning and ending arm positions are shown in Figure 1.…”

“…Two previous clinical trials demonstrated significantly greater gains in motor recovery [4][5][6][7][8], as measured by proximal upper-limb FuglMeyer Assessment (FMA) of motor function [9] scores, at posttreatment in the RA training group than in the control group (CG). However, in both studies the gains in the RA and CGs were equivalent at the 6-month follow-up evaluations.…”

“…However, in both studies the gains in the RA and CGs were equivalent at the 6-month follow-up evaluations. Our first clinical trial enrolled chronic stroke subjects (>6 months poststroke) and compared the results from equal amounts of RA and conventional therapy delivered during 24 sessions over 8 weeks [4][5][6]. The second clinical trial enrolled subacute subjects (after discharge from acute rehabilitation, 1 to 5 months poststroke) [7][8].…”

Retraining of interjoint arm coordination after stroke using robot-assisted time-independent functional training

“…However, in a study of the electromyography (EMG) patterns after training with an end point tunnel controller, a compensatory strategy using excessive shoulder girdle movement appeared to compromise learning of normal reaching patterns [46]. Use of proximal joints in compensatory strategies can be made ineffective with an appropriate control law and an exoskeleton that has direct control of arm joints.…”

Robotic and Mechanotherapeutic Technology to Restore the Functions of the Upper Limbs: Prospects for Development (Review)

“…Another robot aimed at training movements in the shoulder and elbow joints was the Mirror Image Movement Enabler (MIME), developed at Stanford University (USA) [49,50]. This robot allowed training in passive, active-assisting, active-coercion and bimanual modes.…”