Background: In recent years, both telerehabilitation and high-intensity interval training have been studied in connection with patients with Heart Failure (HF). However, these two variables have never been investigated together. The aim of this study was to investigate exercise intensity, perceived safety and exertion of home-based, high-intensity interval training exercise.Design: A non-randomised cross-over study.Methods: Eleven participants with HF (7 men, 4 women; mean age 63.4 years), from the IT IS HOPE 4 HF study, volunteered to participate. After 3 months of twice weekly, high-intensity interval training via telerehabilitation, the participants were asked to perform the last week of intervention wearing heart rate (HR) monitors during both supervised- (live video-conference telerehabilitation) and unsupervised (pre-recorded video) sessions. The outcome was to determine if there were differences between the supervised- and unsupervised sessions in exercise intensity, perceived safety and exertion levels.Results: Eight participants completed the intervention. No adverse events were reported or recorded. Significant differences were found between supervised- and unsupervised exercise modalities when comparing 2nd (86±16 vs 79±16 %HRpeak, p=0.04), 3rd (86±15 vs 81±15 %HRpeak, p=0.03) and 4th (88±16 vs 81±17 %HRpeak, p=0.01) high-intensity intervals (HIIs) and the 2nd moderate intensity active break (82±17 vs 77±15 %HRpeak, p=0.02). All participants felt safe during every recorded intervention. However, no significant differences were found in perceived safety and exertion levels.Conclusion: Telerehabilitation allowed the participants to reach target exercise intensities, while the unsupervised video sessions, did not. However, after 3 months of training, participants felt safe when training both with- and without supervision.