## 4 A Case Study Using PEL
### Study with Stroke Patients
#### 4.1.1 Method  
The quasi-experiment was divided into three stages:  
* **Preparation**. An instructor presented the system to each participant for about 10 min. During the explanation, an example was projected on the wall so that the patient could follow the explanation perfectly and understand the activity to be performed. * **Development**. Each patient performed an exercise routine included in the system according to their condition, which is, if the stroke caused the patient to lose mobility in the left, right, or both parts of their body. * **Evaluation**. Once the patient had completed the previous step, he or she was encouraged to fill in a questionnaire to evaluate the exergames and the software system using _Microsoft One Drive Forms_ ([[https://forms.microsoft.com/](https://forms.microsoft.com/)]([https://forms.microsoft.com/](https://forms.microsoft.com/))), in order to facilitate their subsequent digital processing. The exergames that were performed by the patients were based on rehabilitation exercises to train the upper body, thus involving the arms. All of them were automatically generated from PEL language definitions, when considering both left and right arm versions. Particularly, the exercises associated to the generated exergames were those of (i) bringing the right and left hand from the hip to the shoulder, (ii) bringing the right and left hand from the hip to the mouth, and (iii) bringing the right and left hand from the hip to the head. In addition, (iv) right and left shoulder abduction exercises were performed. Figure 5 shows the visual aspect of some of the generated exergames in the initial version of the rehab system, all of them in the context of a virtual gym. On the other hand, Listing 1 shows the full PEL specification of the exercise right shoulder abduction. At this point, it is important to remark that there exists a normalization process so that, independently of the patient's height and width, the dimensions of the virtual avatar remain the same for every generated game. Each exercise was projected on a large screen. This allowed the patients to correctly visualize the movement that they had to make, as well as the gamification elements provided by the system. The purpose of the test was to analyze the use of the generated exergames by real patients in terms of understanding and adequacy. Thus, the steps defined in [43] were followed, while using a template _Goal-Question-Metrics_. Firstly, patients were asked if they had already used any system of these characteristics in order to find out the advantages or weaknesses that the proposed approach might have with respect to other rehabilitation systems. Then, they were asked to complete a questionnaire with a total of 22 questions (see Table A1 in Appendix A), scored with a Likert scale (1: totally disagree; 5: totally agree), grouped in five dimensions: activity perception, cognitive load, utility, game elements, and the TAM (_Technology Acceptance Model_) framework. These five dimensions are briefly described below. * **Perception of activity**. This dimension is composed of a set of questions to measure interest (INT), effort (EFF), and ease of learning how to use the system (LEA). * **Cognitive load**. This block includes a series of statements inspired by the Cognitive Load Theory (CLT) [44], which allows measuring the cognitive load imposed by the software, the complexity of the developed task (TD) and the complexity that is required by both the software and the device used (DD). In addition, two questions were added to measure the patient's effort in relation to the activity performed (E). * **Utility**. The third block consists of questions related to the patients' opinion regarding the exergame-based rehabilitation system, that is, if they prefer to use it at home instead of attending rehabilitation centers (PREF), if the system encourages them to be more consistent when performing rehabilitation exercises (CONS), if the system enhances motivation (PAS), and if they like the application to look like a game (GAM).