## 4 Discussion
We decided to use as threshold \(\delta\) the [PERSON] and [PERSON]'s limits of agreement [51]. These limits depend on patient variability, which is one of the most important sources of error when assessing changes in this population. Spasticity affects muscle tone and motor skills and induces considerable fluctuations in gait patterns [66; 72]. Thus, this convention brought realism to the data analysis, as it allowed for the personalization of the MBD process according to the specific movement pattern of each individual patient. Nevertheless, using the limits of agreement as threshold \(\delta\) partially deviates from the nature of the MBD method, which was created to calculate the probability that a change will have a practical effect on an individual using MIDs. In addition, it could be said that our approach was closer to the null-hypothesis significance test [37; 71] which searches for non-zero (not null) changes. For this reason, we do not consider the limits of agreement the definitive solution. Instead, we consider these limits to be an instrument introducing the MBD method to assess individual patients. We hope that our study will expand the debate regarding which threshold \(\delta\) to use in gait analysis to assess an individual patient's changes. An alternative option regarding threshold \(\delta\) is to use the minimal detectable change (MDC). This figure could be calculated by conducting a reliability study with a month between trials among a group of patients with spasticity similar to the patient being studied [2; 46; 52; 53]. Nevertheless, there is a key difficulty in finding a homogeneous sample of patients such as these [15; 63]. Furthermore, this threshold \(\delta\) shares limitations with the [PERSON] and [PERSON]'s limits of agreement used in this study, since it is also used to seek non-zero (not null) changes but not for practical changes. For this reason, we agree with [PERSON] and [PERSON] [37] and [PERSON] [47], who explained that the optimal choice for the threshold \(\delta\) is to use the MID value [46]. To the best of our knowledge, no previous studies have calculated MID values of spatiotemporal or kinematic variables resulting from a MoCap gait analysis system for patients with spasticity. MDI was calculated for the _GaitSpeed_ variable, and though this measure can be taken readily with a chronometer; it was examined in patients experiencing stroke [72; 73; 74] or other pathologies [75] than the one in this study. Thus, we propose that studies be conducted to calculate MID indexes for gait variables using anchor-based methods [76]. Determining MID values in this area is complex due to the aforementioned difficulty of finding homogenous samples, as well as the numerous variables generated by a MoCap gait analysis system and the combined biomechanical interpretation it requires. However, such complexity should not hinder investigations to generate MID values for gait variables or for gait indexes that combine them [77]. Studies of this kind would reinforce clinical decision-making and the individual analysis approach described here. As previously mentioned, based on the interpretation process, which is included as Supplementary Materials, a series of interpretation guidelines to classify changes as either improvements or impairments have been proposed. These guidelines are ordered from the most general, which affect all of the variables, to the most variable-specific guidelines, as listed below:  
* Improving symmetry is beneficial. A change is positive when the values for the healthy and affected legs are closer in the second session [78]. * Increasing _GaitSpeed_ is a highly positive change, as it is associated with functional improvement [72; 73; 74]. * Decreasing the _Pelvic.Tilt_ or _Chest.Tilt_ is interpreted as a positive change, as it implies lower energy cost and greater stability [56]. * Increasing the _StepLgth_ is considered to be positive, except if it is due to uncontrolled or involuntary movement [56] (noticeable when _StepLgth_ presents high variability).