High‐intensity interval training vs. moderate‐intensity continuous training in COVID ‐19 survivors ( COVIDEX ): A randomized clinical trial on feasibility and short‐term efficacy

Abstract

Background High-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) have been widely studied in individuals with chronic conditions. However, no studies have compared these two exercise modalities in COVID-19 survivors. Objective To compare the feasibility, safety, adherence, and short-term efficacy of HIIT and MICT in improving functioning and health-related quality of life in COVID-19 survivors. Design Two-arm, parallel-group, single-center randomized clinical trial with a 1:1 allocation ratio, conducted according to intention-to-treat principles and designed as a precursor to a future definitive randomized clinical trial. Setting A specialized post-COVID-19 rehabilitation center. Participants Thirty COVID-19 survivors treated at a post-COVID-19 rehabilitation center. Interventions HIIT (4 × 4 minutes at 85%-90% of peak heart rate) or MICT (40 minutes at 70%-75% of peak heart rate), both performed twice a week with isocaloric protocols for 4 weeks. Main outcomes measures Eligibility and consent rates, attendance, retention, ability to achieve the prescribed intensity and duration, completion of the recommended sessions, adverse events, cardiopulmonary exercise testing, as well as other physical performance tests, questionnaires, and specific scales. Results Eligibility and consent rates were 80% and 62.5%, respectively. One participant in the HIIT group and two in the MICT group discontinued the interventions. Attendance was 8 (7-8) sessions in the HIIT group and 7 (6-8) sessions in the MICT group. Both groups were able to achieve the prescribed intensity and duration, and no serious adverse events occurred in either protocol. Regarding short-term efficacy outcomes, no differences were observed between the two protocols for any variable. Conclusion Both protocols appeared feasible, with similar short-term efficacy for functioning and health-related quality of life, demonstrating good adherence and safety. However, a definitive trial will be necessary to confirm these findings. Trial registration Brazilian Clinical Trials Registry (REBEC: RBR-5tvjs5t).