Introduction: Patients with implantable cardioverter defibrillator require physical therapy due to their decreased physical fitness. This is why standardized training has been designed for groups of subjects of varying endurance. Material and methods: Patients with heart failure and implantable cardioverter defibrillator who wished to do interval training program. The program included 55 patients. We divided them into two study groups. The first group had lower exercise tolerance level (3.94 ± 0.72 MET), and the other had higher exercise tolerance level (7.97 ± 1.80 MET). The training group had an 8-week long training program. The patients received treatment at an outpatient clinic three times a week. Patients had cardiac stress tests with modified Bruce protocol before receiving physical therapy and after they have finished the training program. We assessed the metabolic equivalent of task (METS), the duration of exercise, blood pressure, heart rate and BMI. Results: We observed longer duration of cardiac stress test performance and improvement of exercise tolerance. In patients from the group with lower exercise tolerance, the level of exercise tolerance was 3.94 ± 0.72 MET before therapy and rose to 5.93 ± 1.12 MET (p < 0.001) after therapy. In the group of higher exercise tolerance, the level was 7.97 ± 1.80 MET before therapy and rose to 9.32 ± 2.01 MET (p < 0.001) after the training cycle. Conclusions: Participation in 8-week interval training cycle resulted in greater increase of exercise tolerance and exercise time, as well as hemodynamic parameters in patients with lower exercise tolerance.