Contents lists available at ScienceDirect Journal of Biomedical Informatics journal homepage: www.elsevier.com/locate/yjbin Serious games for rehabilitation: Gestural interaction in personalized gamified exercises through a recommender system Carina S. González-González a, ⁎ , Pedro A. Toledo-Delgado a , Vanesa Muñoz-Cruz a , Pablo V. Torres-Carrion b a ITED Research Group, Department of Computer Science and Engineering, Universidad de La Laguna, Spain b Inclusive Human Computer Interaction, Department of Computer Science and Electronics, Private Technical University of Loja, Ecuador ARTICLE INFO Keywords: Recommender systems Exergames Rehabilitation Gamification Serious games ABSTRACT One of the principal problems of rehabilitation is that therapy sessions can be boring due the repetition of exercises. Serious games, and in particular exergames in rehabilitation, can motivate, engage and increase pa- tients’ adherence to their treatment. Also, the automatic personalization of exercises to each patient can help therapists. Thus, the main objective of this work is to build an intelligent exergame-based rehabilitation system consisting of a platform with an exergame player and a designer tool. The intelligent platform includes a re- commender system which analyzes user interactions, along with the user’s history, to select new gamified ex- ercises for the user. The main contributions of this paper focus, first, on defining a recommender system based on different difficulty levels and user skills. The recommender system offers the ability to provide the user with a personalized game mode based on his own history and preferences. The results of a triple validation with ex- perts, users and rehabilitation center professionals reveal a positive impact on gestural interaction and re- habilitation uses. Also, different methods are presented for testing the rehabilitation recommender system. 1. Introduction Nowadays, serious games, and in particular exergames, are being used by therapists as a tool for rehabilitation purposes [51,36,66,27]. Exergaming involves physical exertion, and is directly related to the exercise in the game, not to the game or exercise itself. An increasing number of studies have introduced exergames in rehabilitation with the goal of motivating, engaging and increasing patient adherence to their treatments [56,63,54]. The research confirms the motivational benefits of using exergames in rehabilitation, regardless of the age of users or their illness [6,49,5]. In 2018, Camilo et al. presented two user ex- perience evaluations based on two games developed using an iterative user-centered methodology with results that showed that game use may increase patient motivation [13]. Some researchers have been using commercial exergame platforms such as Wii or Xbox games for physical rehabilitation, but they cannot satisfy the full requirements of the re- habilitation therapy. It is important to note that the game should not only allow assigning exercises to users, but also give recommendations on how to perform the exercise. Furthermore, another typical problem in this context is that the therapist needs to design his own exercises for each particular rehabilitation and create a plan tailored to the specific characteristics of each patient or group of users with similar needs. In other contexts, exergames also can be used to develop psychomotor competencies, which include fundamental motor skills (coordination, balance, posture, body schema and image), perceptual motor skills (spatial and temporal skills and rhythm), and cognitive skills (reasoning and memory) [16]. To address these issues, we have created a platform named TANGO:H (Tangible Goals: Health) that can be used to design active games to rehabilitate hospitalized children [28]. TANGO:H was created as an open platform that allows professionals to design different types of rehabilitation exercises for different pathologies, and it has been used by several rehabilitation centers for different purposes. Gamification and Serious Games in rehabilitation is a current area of research. One of the principal problems of rehabilitation is that therapy sessions can be boring. These sessions normally consist of repeating the same exercises again and again. Games can help to improve motivation and make patients work harder [56,54]. This research seeks to answer the following research questions: https://doi.org/10.1016/j.jbi.2019.103266 Received 27 December 2018; Received in revised form 21 July 2019; Accepted 4 August 2019 ⁎ Corresponding author. E-mail addresses: cjgonza@ull.edu.es, carina.gonzalez@ieee.org (C.S. González-González), petode@ull.edu.es (P.A. Toledo-Delgado), vmunoz@ull.edu.es (V. Muñoz-Cruz), pvtorres@utpl.edu.ec (P.V. Torres-Carrion). Journal of Biomedical Informatics 97 (2019) 103266 Available online 10 August 2019 1532-0464/ © 2019 Elsevier Inc. All rights reserved. T