## 4 Discussion  
Gait recovery is a key factor for the restoration of satisfying levels of participation and quality of life in stroke subjects. In literature, many treatments have been proposed, but there is not a general consensus on their effects [2]. In this context, robotic technologies have been recently widespread in rehabilitation, and their efficacy has been demonstrated in clinical studies [3; 5; 6; 12; 16]. However, to our best knowledge, no evidence is available on which robotic technology is more effective for gait training in stroke subjects [15; 19]. Therefore, the aim of this pilot study was to compare the effects of t-RAGT, o-RAGT, and CGT in stroke subjects by means of clinical and gait assessments.  
Twenty-six stroke subjects were recruited for the study. Each treatment was well tolerated by all subjects and proved to be safe. We obtained a full complete adherence to the protocol, considering that all subjects completed the training sessions, without any drop-outs. No adverse event occurred.  
Results on clinical outcomes showed significant pre-post differences in most ICF domains: each group registered improvements between the baseline and final assessments, but these differences were not significant among them. In TUG, 10 MWT, and 6 MWT, although the statistical significance was not obtained, pre-post differences on GG end EG were higher than the MDIC values reported in literature [16]. Such outcome was not found in CG. These results are encouraging and consistent with the literature on the effects of t-RAGT [13] and o-RAGT [11] with the same devices. Specifically, [PERSON] et al. [13] studied the efficacy of end-effector t-RAGT in 14 subjects with chronic stroke, and found significant higher pre-post differences in 6 MWT in the robotic group, but no variations in spasticity. The recent observational study by [PERSON] et al. [11] on o-RAGT in 48 stroke subjects found similar clinical outcomes: significant improvement in the majority of clinical assessments, in speed measured during 10 MWT, and in the distance covered over a time of 6 min (6 MWT).  
Results on spatio-temporal gait parameters showed no significant pre-post and between-group differences. Data from gait analysis are consistent with findings reported in subjects after stroke [13; 18; 35] and traumatic brain injury [23] who conducted RAGT. Specifically, no within- and between-group differences were registered in spatio-temporal gait parameters after neither t-RAGT nor CGT in chronic stroke subjects [13]. Similarly, the study by [PERSON] et al. [35] on stroke subjects found that t-RAGT did not improve gait parameters. The study by [PERSON] et al. [23] that compared three different gait trainings (BWS treadmill, end-effector t-RAGT, and exoskeleton t-RAGT) in subjects with traumatic brain injury confirmed our findings, i.e., no inter-group differences occurred in gait parameters.  
This study presented several limitations that deserve to be discussed. Firstly, the lack of the randomization may have maximised the selection bias. It was not possible to meet the need for randomisation because the clinical centres who participated to the study did not have both robotic devices available. Secondly, the sample size could be considered limited, and it could have influenced the statistical relevance and the power of this study. However, findings that came from this pilot study could provide the basis for a larger clinical trial. Finally, the study did not analyse the joint kinematics and kinetics: this choice in study design was purposed by the necessity to face our results with published studies on the topic [13; 23; 35]. Hence, the research agenda should include the implementation of future multicentre studies, the recruitment of more subjects, the analysis of joint biomechanics, and the inclusion of neurophysiological measurements (i.e., electromyography, electroencephalography).