# A Meta-Analysis on Dual Protocols for Chronic Stroke Motor Recovery: Robotic Training and tDCS
###### Abstract
A second stroke rehabilitation protocol that has recently become popular is robotic-assisted movement [26; 27]. Essentially, impaired limbs are moved through a range of movements programmed for specific joints. Robot assistance has been applied to both upper and lower extremities with encouraging results [28; 29]. One critical advantage of this rehabilitation protocol is that a high number of repetitions can be completed in every training session [30]. Increasing the number of assisted movements and the consistency in the motor actions generally produce improved genetic limb performances as well as an increased range of functional motions [30; 31; 32]. Taken together, the accumulated quantitative data from several prior meta-analysis studies indicated that robot-assisted therapy effectively improved motor control capabilities, muscle strength, and gait/balance functions post-stroke [29; 33; 34]. Further, some researchers suggested that robotic-assisted movements combined with additional rehabilitation protocols (e.g., physiotherapy or body-weight support training) may increase motor improvements beyond the effects of robotic training alone [29; 35]. Given the elusive nature of effective and efficient stroke motor recovery protocols, researchers have begun combining two novel approaches for the purpose of optimizing rehabilitation effects on paretic limbs [36; 37]. Indeed, providing tDCS before or during robotic treatments has high learning potential for recovering treated motor actions. Augmenting robotic training with tDCS appears to activate favorable movement action re-acquisition conditions in the primary motor cortex and the supplementary motor area [38; 39]. That is, priming the motor system while performing an extended set of repetitive robotic-assisted movements has been embraced in the rehabilitation arena. Indeed, prior studies have reported that tDCS priming facilitated motor improvements in individuals post-stroke when this technique was employed with high intensity and task-specific motor training designed to activate neuroplasticity and motor learning [40; 41]. However, two recent systematic review and meta-analysis studies reported insufficient evidence regarding the beneficial combined effects of tDCS and robotic training on stroke motor rehabilitation [42; 43]. Importantly, these findings were limited to functional recovery of the upper extremities, with a relatively small number of analyzed studies. A third meta-analysis study followed different inclusion criteria and found slightly expanded potential effects of robotic-assisted movements combined with tDCS by demonstrating moderate positive effects in the lower extremities post-stroke [44]. Moreover, these three sets of meta-analytic findings predominantly focused on transient performance effects (i.e., short-term retention) of the combined training protocols. Considering the conflicting findings and limited number of comparisons in the previous meta-analyses, a convincing answer to the question regarding the additive effects of combining robotic-assisted movements and tDCS as stroke rehabilitation protocols is missing. Further, determining whether functional recovery of the upper and lower limbs improves after delayed retention testing is still unknown. Thus, combining two effective individual rehabilitation protocols and simultaneously administering both of them is a novel approach to minimizing long-term motor dysfunctions post-stroke [45; 46]. Given the increased number of publications reporting the separate effects of tDCS and robotic training, a question arises concerning the additive effect of dual protocols. Thus, our purpose was to conduct a systematic review and meta-analysis to determine the overall effects of the two augmented protocols [36; 47] on post-stroke motor recovery in the upper and lower extremities.