## 2 Material and Methods
### VR Application  
The FarmDay application was developed using the Unity3D game engine v.2019.2.13f, mainly using the collection of scripts and predefined elements of the Virtual Reality ToolKit (VRTK) v.3.3.0 framework. This open source toolkit was used to implement the virtual space locomotion, object grasping interactions, object interaction via pointers, 3D button interactions, and 3D body physics within the virtual space. 1. VR framework and platform As stated before, and due to the custom real-time remoting system developed in OpenVR, it was consequently determined that the VR application should be built for systems compatible with the OpenVR platform. Then, FarmDay was designed for the OpenVR SDK (Software Development Kit), so the real-time remote system can be used. The VR application was developed entirely as a single Unity scenario. In this 3D scenario, six activities are distributed through specific areas of the environment. For interactive actions and locomotion control, the VRTK prefab module was used. The VR solution generated supports the HTC ViveTM and Oculus RiftTM platforms' controllers, which are used for the interactions. 2. Gamification elements The gamification strategy of the activities included in the FarmDay experience is based on goal achievement. Thus, each activity is composed of a sequence of actions that the user  
Figure 1: Diagram of the the real-time, remote VR system architecture. must perform to complete the task. The achievement of these objectives implies that the motions of the different body segments involved in the ADL functional movements were properly performed. 3. Design of activities  
Of the six activities offered by the application, three are based on real-life situations and were designed following the guidelines and advice of five physiotherapists specialised in neuromotor disorders from the Spinal Cord Injury Foundation (Fundacion de Lesionado Medular, FLM) and CEU San Pablo University (Universidad San Pablo CEU, USPCEU). They are hand-washing, pouring a drink, and playing the piano. The three remaining activities were themed around farm life and designed to involve movements similar to ADL. They are animal caring, picking apples from trees, and picking vegetables up off the ground. This way, the user can perform a bigger variety of exercises, hopefully increasing their adherence, reducing the feeling of boredom, and allowing them to work on similar movements in different ways. 4. User Interaction  
The FarmDay application begins by placing the user at the entrance of the farm, allowing them to explore the environment by moving around the delimited physical space, either by directly walking or by using a teleport functionality that can be activated with any of the two controllers. Additionally, game selection panels have been distributed throughout the environment. Through them, the user can teleport from one activity to another without having to physically traverse the VE. These game selection panels consist of six interactive buttons that react when pressed with the controller, moving the user to the zone of the selected activity. The zone for each activity has a floating transparent panel which shows the objective of the activity and contains a play button. When the user presses the play button (by moving their hand), this game panel fades out and the activity starts. Once the activity is completed, the game panel fades in again, allowing the user to repeat the activity as many times as desired, restoring all the environment elements to their initial positions. Design of Activities  
Since each of the six activities aims to make the user perform movements specific to a particular ADL, it was essential to identify such movements. It was also necessary to determine the range of motion (ROM) for each joint (neck, shoulder, elbow, and wrist) and action, to make the tasks' movements as faithful as possible to what the user would do in a real-world ADL.