## 4 Discussion
### Variable/Concept under Study and Test Procedures  
The concept/variable to be evaluated is referred to using a variety of terms, including spasticity [17; 20; 28; 30; 32; 33], muscle tone [17; 20; 28; 29] or even increased muscle tone [28; 30; 33], and this notion is consistent with that reported by [PERSON] et al. [22]. Variations in the existing definitions in the literature about muscle tone and its changes make it difficult to interpret or measure, leaving room for professionals to create their own version [5]. The lack of a clear conceptual framework prevents effective communication between professionals and the quantification of results that are based on an unequivocal conceptualization [22], interfering with decision-making to outline the best intervention strategies and procedures in a clinical context. The literature attempts to overcome this difficulty and has tried to homogenise the conceptualisation of the different conditions of muscle tone, providing more concrete definitions depending on the occurrence. In 2018, [PERSON] [8] presented a summary of the variations and the underlying neurophysiological characteristics in order to improve understanding and to provide clear conceptual definitions. This information could provide necessary insights for a better approach for practical contact with patients regarding physiotherapy evaluations and consequent interventions. It was proposed that, in an awake person with a normal neuromuscular system, slight muscle resistance to passive stretch is normal, and muscle tone is categorized on a continuum. The resistance ranges from flaccid (complete lack of resistance) to abnormally low (hypotonia), to normal, to velocity-dependent hypertonia (abnormally high resistance that increases with faster movement), and finally to rigidity. According to the continuum and regarding the concepts identified in this study, namely, spasticity, muscle tone, or increased muscle tone, it is important to highlight how these concepts are being defined in literature (Figure 3) to better analyse the studies that were summarized in this review. While applying the clinical instruments identified, the authors included in this study followed the provided instructions for each instrument used in the testing procedures. Considering the definitions of muscle tone in the presence of CNS alterations, particularly its increase (Figure 3), it is essential to explore the response to the passive mobility of the joints under study, taking into account the velocity and the electromyographic activity of the muscles involved. Of the studies included in this review, two of them [17; 20] considered some of these aspects and complemented MAS application with EMG evaluation. Only [PERSON] (2021) considered velocity during the texting procedure because the study followed the Montreal Spasticity Measurement clinical instrument instructions. It seems necessary to clarify how the different authors defined the concept under study. Specifically, if spasticity is velocity dependent, it is not sufficient to evaluate it with MAS or MMAS. It is also important to determine whether it is being used correctly for the concept under study. According to recent definitions (Figure 3), if velocity is not being considered, it may not be appropriate to define the concept under study as spasticity. Nowadays, given the current challenges in rehabilitation and the different contexts of action, among which home-based physiotherapy also stands out, it is crucial to follow a patient-centred approach adapted to individual needs to promote more natural and  
Figure 3: Definition of normal muscle tone and muscle tone in the presence of increased resistance [8]. efficient rehabilitation. In addition, homogeneous assessment and decision-making among professionals as well as concordant forms of assessment are crucial.