Could High-intensity Interval Training be Inappropriate in Pulmonary Rehabilitation of COVID-19 Recovered Patients? Opinion Article

Pulmonary rehabilitation is a multidisciplinary intervention recommended by international guidelines in managing COVID-19 patients and/or post-COVID-19 conditions with mid-and long-term complications of the initial illness. Physiotherapy-based pulmonary rehabilitation has received considerable attention since the COVID-19 pandemic, with supervised exercise training probably the most important component. Current guidelines clearly encourage low- to moderateintensity exercises for COVID-19 recovered patients and discourage high-intensity/vigorous exercises. However, the ongoing interest in high-intensity interval training (HIIT) has extended to post- COVID-19 rehabilitation based on its efficacy and safety in other patient populations. In this perspective, several reasons behind the possibility of the inappropriateness of the HIIT in post-COVID- 19 conditions will be discussed and supported by evidence. In addition, the key points for safe exercise after COVID-19 illness will be listed.