# An Agile Approach to Improve the Usability of a Physical Telechabilitation Platform
## 3 Materials and Methods  
In the rehabilitation process, patients permitted the capture of their correct and incorrect movements with the help of the Kinect equipment. This equipment captures the three-dimensional coordinates (X, Y, Z) of the 25 main joints of the human body as show on Figure 1. Information preprocessing was carried out to identify the relevant information, eliminating repeated data as well as noise as presented in Reference [29]. According to a study conducted by [PERSON] [30], it is not possible to detect 100% of usability problems. In this study, we started with the usability evaluation of an exploratory prototype. This evaluation was a first agile approach aimed at detecting the majority of usability problems and was refined posteriorly to identify any minor remaining issues. For the posterior analysis, it was decided to have the collaboration of a minimum of three usability experts in the first, second, and third iterations. With six experts collaborating in the fourth iteration. This, according to the [PERSON] study, would guarantee to find 75% of the usability problems. To perform the heuristic evaluation, [PERSON]'s 10 heuristics principles [24] and three specific heuristics detailed in Table 1 were used. This set of heuristics was complemented with three specific heuristics as suggested by Reference [31]. The cognitive walkthrough was made with the help of volunteers that completed a demographic survey of 40 questions aimed to understand their background regarding gender, age, experience using computers, ability to learn software packages, experience using computer games, and experience using Kinect or similar gesture user interface devices. The first phase was composed of two exploratory iterations. A prototype was used in order to validate the user's requirements. The second phase was also composed of two iterations of refinement. In addition, an instrument called NASA-TLX [32; 33] was added to perform the evaluation of the workload of patients when performing tasks on the ePHoRT platform. The platform is designed to work with patients after hip replacement surgery. However, government regulations require a complete version of the platform in order to authorize experimentation. For this reason, the evaluation was made with the help of volunteers. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Id** & **Heuristic Principles** & **Id** & **Specific Heuristics** \\ \hline HP1 & Visibility of system status & SH1 & Feedback \\ HP2 & Match between system and the real world & SH2 & Physical constraints \\ HP3 & User control freedom & SH3 & Extraordinary users \\ HP4 & Consistency and standards & & \\ HP5 & Error prevention & & \\ HP6 & Recognition rather than recall & & \\ HP7 & Flexibility and efficiency of use & & \\ HP8 & Aesthetic and minimalist design & & \\ HP9 & Help users recognise, diagnose, and recover from error & & \\ HP10 & Help and documentation & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: [PERSON]’s 10 heuristics principles and three specific heuristics. Figure 1: Body points sensed by the Kinect device. The first iteration began with the selection of three relevant interfaces from the exploratory prototype: Login, Questionnaire, and Exercise Assessment. These interfaces were selected using the following criteria [27]:  
* The login interface is the main gate to the ePHoRT platform. The interface also provides security of the resources assigned to the user and user identification for progress monitoring purposes. * The questionnaire interface must be completed by the user before doing the rehabilitation exercise. This interface defines whether the user is sufficiently healthy to practice. * The exercise assessment interface is one of the set of interfaces that presents the 129 physical exercises and provides instructions to the patient. The results of the evaluation of the sample interfaces were organized as a list of improvements ordered by severity.