The VR group will perform the endurance exercise training using the "Virtual Park", developed by CNR-STIIMA. The system includes a COSMED cycle-ergometer, a virtual environment and a physiological sensor-either a HR band or a pulse-oximeter depending on the target patient's needs. The virtual environment represents a ride in a park, enriched with realistic elements and sound effects, in order to simulate a daily life situation.

In the VR group, the VR Tier One device (Stolgraf®) will be used as a VR source. Thanks to using a head mounted display and the phenomenon of total immersion, VR therapy provides an intense visual, auditory and kinaesthetic stimulation. The aim of the software was to calm and improve the mood, while motivating and cognitively activating the patient.

In the TPR group, exercise training will be performed on the bicycle. The training will be conducted on cycle ergometers with the use of the Peloton™ system, which ensures the monitoring of performance parameters.

In the TPR group, Schultz Autogenous Training will be performed. Schultz Autogenic Training has been shown to be effective in treating these pathologies. In both groups the relaxation training will be carried out once a day and will last about 20 minutes.

An in-patients 3-week high intensity rehabilitation program, five times a week, was used as the intervention treatment. A holistic pulmonary rehabilitation program for SARS-CoV-2 patients with combined treatment focused on increasing exercise capacity, restoring lung function, and supporting mental health, developed by a multidisciplinary team, was introduced. Rehabilitation program includes exercise capacity training on a cycle ergometer, breathing exercises, general fitness exercises, resistance training, and relaxation.

Spirometry testing will be performed in all patients before and after rehabilitation. For the assessment of respiratory function, the following indicators will be used: forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and FEV1 percentage obtained the current VC (FEV1%). The measurement will be performed three times by the patient and the best result will be included in the research study.

In all patients, prior to and immediately after the 6-minute walk test, an assessment of dyspnoea will be made by the 10-degree Borg scale, which is the most versatile and most widely used scale for breathlessness. This method will allow for comparison of the absolute level of breathlessness patients feel at a given exercise intensity. A lower score means less impairment

The Perceived Stress Scale (PSS) is the most widely used psychological instrument for measuring the perception of stress. It is a measure of the degree to which situations in one's life are appraised as stressful. Items were designed to tap how unpredictable, uncontrollable, and overloaded respondents find their lives. The scale also includes a number of direct queries about current levels of experienced stress. A lower score means less impairment

The HADS is a 14-item scale, scoring each item from 0 to 3. The first seven items relate to anxiety (HADS-A), and the remaining seven items relate to depression (HADS-D). The global scoring ranges from 0 to 42, with a cut-off point of 8/21 for anxiety and 8/21 for depression. The higher the score is, the greater the anxiety or depression symptoms. The scale is considered to be a valid research method.

During trainings, Polar H10 monitor (Polar Electro Oy Inc., Kempele, Finland) will be employed to record HR series at a sampling frequency of 1000 Hz. The device is recommended as the gold standard for R-R interval assessments during intense activities to obtain HR and HRV. All HRV analyses will be carried out with the Kubios HRV Premium version 3.3.1