## 4 Discussion
At the end, for the sake of deploying the research results at home, we added a pen controller that can help controlling the system in certain cases as the voice commands of Kinect sensor fails when there is noise in the environment. Other studies have used RGBD sensors for the measurement of the FRT. Though having different gold standards and settings, our findings align with theirs in terms of validity of the test and its reliability. We had very strong correlation with manual FRT with values of (r = 0.97, \(p\) < 0.05) and (r = 0.99, \(p\) < 0.05) in the first and second experiments, respectively, where [PERSON] et al. [49] also reported a strong correlation (r = 0.719, \(p\) < 0.001) of Kinect v2 results with traditional FRT. In their study, [PERSON] et al. [36] computed the reach distance through trunk flexion measurements and concluded that Kinect could be used in instrumenting the reach test by providing excellent validity for trunk angle data (r = 0.93, \(p\) < 0.05). These findings maintain valid using PrimeSense camera as well, [PERSON] et al. [33] acquired kinematic data from both PrimeSense and inertial sensors intertiaCube3 TM as benchmark for the parametrization of MDRT, and comparisons revealed strong correlation in most of the evaluated variables of the test. In terms of reliability, we obtained good to excellent within repeatability of the test using our system (ICC = 0.86 in Experiment 1 and ICC = 0.99 in Experiment 2). From their side, [PERSON] et al. [49] found a good repeatability (ICC = 0.82) of the measurements of the second and third trials of forward reach obtained by Kinect v2. Moreover, [PERSON] et al. [35] assessed inter-trial reliability of forward reach and reported comparable good Kinect reliability (ICC = 0.72) with 3 DMA reliability (ICC = 0.81). This is consistent with the excellent intrarater reliability of the original test [50]. Furthermore, RGBD devices can be a great tool for fast screening for balance problems as they proved to be valid and reliable, they also provide user feedback which is reported important to improve adherence in rehabilitation. Furthermore, they have the advantage of capturing other parameters that might be of interest of therapists such as time and velocity of doing the test [33; 49], differentiating the movement strategy [51], among others. These parameters can be used for better assessing the balance ability of people with balance deficiencies. The limitation of the study is that the system was tested in laboratory conditions. Further validations performed by different patient populations in real situations could generalize our findings. Nevertheless, different studies showed that FRT can be used as an index for fall prevention [52; 53; 54; 55]. Finally, we want to remark that the proposed system can be considered transparent [56], because has the ability of simulatability (being simulated or thought about strictly by a human), decomposability (explaining each of the parts of the method), and algorithmic transparency (the user can understand the process followed by the method to produce any given output from its input data). This is especially critical in health, to trust the behavior of systems.