Qualification scheme for the research
The examined patients were randomly divided into two groups: study group and control group depending on the assigned intervention. The study group consisted of patients undergoing renal replacement therapy by hemodialysis, whose task was to perform VR exercises using the prototype of the NefroVR system for 20 min during hemodialysis. The exercises was conducted three times a week during the first (1–2) hours of HD treatment or until UF 2.5 was achieved.The control group consisted of patients undergoing renal replacement therapy by hemodialysis who were not assigned a task.A prototype of the NefroVR system was used for the study. The system consisted of the following components placed on a mobile platform with ballast:a base unit (responsible for connecting all components and running dedicated software)a rehabilitation rotor with a flywheel and a manually adjustable load (for exercises during dialysis)a panoramic screen for the patienta touch control screen (for the person operating the device—a doctor, nurse, or physiotherapist)a control kit (for the patient)—digital joystick and one button.The device operated on the basis of audio-visual stimulation that provoked the patient's physical activity. The patient connected to the device participated in a virtual experience—in a game where movement was only possible with the rehabilitation rotor included in the device. The speed of the rotor rotation had an impact on the patient's pace in the game. The doctor/physiotherapist treating the patient was responsible for selecting the appropriate ratio of the number of rotor revolutions to speed in the game and for the physical resistance of the flywheel in the rotor. These parameters had to be matched to the patient's current health condition, so that the load was not too intense (e.g., too high heart rate or blood pressure drop/increase below/above the permitted values). In the clinical trial phase, patients had a choice of 5 mini-games, the gameplay of which was scheduled for about 15–20 min. In addition to the rotor control, the patient had additional interaction options via a digital joystick and one button. The level of interactivity available to the patient at the stage of clinical trials was limited to such an extent as to minimize the time needed to introduce the patient to the NefroVR system.Data were collected twice: at the time of joining the research project (E0), after the third month (E3). The approval of the Bioethics Committee No. KB-0012/144/2020 of 5 October 2020 was obtained to conduct the research project.