# A Meta-Analysis on Dual Protocols for Chronic Stroke Motor Recovery: Robotic Training and tDCS
## 4 Discussion  
The current systematic review and meta-analysis investigated the potential effects of robotic training programs in addition to tDCS protocols on motor recovery of the upper and lower extremities post-stroke. In contrast, analysis of the studies focused on the lower extremities revealed significant motor improvement findings for both moderate transient and sustained learning. Positive short-term and long-term motor effects were found for the augmented robotic training and tDCS protocols. These significant overall gait improvements were confirmed for individuals in the chronic stage of stroke recovery. The meta-analytic findings on the upper extremity studies showed insufficient evidence regarding treatment effects of tDCS in addition to robotic-training programs. This is consistent with two recent review studies [42; 43]. Specifically, the systematic review results on the eight individual studies performed by [PERSON] and colleagues argued that robotic  
Figure 5: Long-term effects of robotic training combined with tDCS on lower limb functions. The synthesized data derived from a random-effects model show significant positive sustained effects on lower motor rehabilitation. Note that the red diamond indicates overall effect size and squares denote individual effect sizes with 95% CI. More positive values indicate more treatment effects after the combined protocols [37; 53; 57; 64]. training coupled with tDCS protocols led to similar clinical improvements in upper limb functions post-stroke as compared with the robotic training protocol only [43]. Similarly, a meta-analysis reported no significant additional effects (mean difference = 0.15 with \(p\)-value = 0.93) of non-invasive brain stimulation (NIBS) protocols, including tDCS (i.e., six studies) and continuous theta burst stimulation (i.e., one study), combined with robotic training on upper limb motor recovery in patients with stroke [42]. [PERSON] and colleagues suggested the possibility that the association of NIBS and robotic training may reveal long-term motor improvements in the upper limbs rather than short-term effects. However, our meta-analytic findings confirmed that the sustained effects estimated at 2-12 weeks after administering the final tDCS intervention were not significantly positive. Moreover, the potential treatment effects of robotic training protocols on paretic arm recovery were controversial. Several meta-analysis studies argued that functional improvements in the upper extremities post-stroke (e.g., motor functions, muscle tone, and activities of daily living) were comparable between robotic training protocols and dose-matched conventional rehabilitation programs [27; 34; 73; 74; 75]. Despite some meta-analytic findings that reported significant improvements in motor control and strength of the paretic arms, the magnitude of motor recovery evidence was relatively small (e.g., two points of FMA arm score and Hedges' g = 0.25) [34; 76] and insignificant in the random-effects model [75]. Some studies suggested that quantifying kinematic and kinetic outcome measures may effectively detect changes in upper limb functions and motor learning after robotic training protocols for certain patients with stroke [34; 77]. Patients, at three months post-stroke, may adapt their motor actions and prefer compensatory behaviors for daily living instead of the behavioral restitution of neurological impairments that would indicate true recovery [78; 79]. Thus, clinical measurements are presumably insensitive for differentiating exactly what to learn (i.e., behavioral restitution) from the use of compensation strategies, and this limitation may potentially influence insignificant motor improvements of the paretic arms after robotic training combined with tDCS protocols. In fact, two individual studies in the current meta-analysis reported positive trends in functional improvement for patients with chronic stroke, as indicated by kinematic outcome measures on paretic arms (e.g., aim and straightness during upper limb reaching movements) [55; 58].