2.5. Training Program
Both the study and control groups underwent a controlled endurance training process on a bicycle cycloergometer (Kettler DX1 Pro, Ense, Germany) for 3 weeks. The subjects completed 12 training units under the supervision of a physical therapist and a physician. A single training session was 50 min long and consisted of a 5 min warm-up, 40 min of specific training, and 5 min of unloaded cycling. Until the heart rate returned to pre-exercise values, the patient stayed on the cycloergometer.Patients assigned to the study group received additional intervention in the form of the supplementation of the breathing mixture with oxygen at the flow of 6 L/min during the training sessions. Oxygen was administered via an intranasal cannula using a Korgiel MTO