Exercise rehabilitation in post COVID-19 patients: a randomized controlled trial of different training modalities.

Background: Long-lasting symptoms (>12 weeks) following a COVID-19 infection are defined as the post-COVID-19 syndrome (PCS), often manifesting as fatigue and reduced exercise capacity. Thus, exercise has been suggested as a non-pharmacological therapy.

Aim: To investigate the effects of endurance vs. concurrent exercise on physical function, symptoms and quality of life in individuals with PCS, that did not need hospital admission during acute COVID-19.

Design: Parallel-group, single-center, randomized controlled trial.

Setting: This study was conducted at the University of Vienna.

Population: Adult individuals with a SARS-CoV-2 infection at least 12 weeks prior to enrollment who reported at least one symptom specific to PCS and did not experience post-exertional malaise.

Methods: Participants were randomized to either 12 weeks of supervised endurance training (ED) or concurrent training (CT), or a non-exercising control group (C). As the primary outcome, VO2peak was assessed pre and post intervention. Secondary outcomes were handgrip and lower body strength, heart rate variability, symptoms, health-related quality of life (HRQoL) and concentration performance. The main effects for time and group as well as the time*group interaction were assessed via a 2x2 analysis of variance. Additionally, within-group pre-post testing was performed.

Results: Taking the study protocol into account, 42 subjects could be included in the analysis (N.=14 in each group). A significant time*group interaction favoring both exercise conditions was found for VO2peak (partial Eta=0.267; ED: +3.9 mL/min/kg; CT: +3.2 mL/min/kg). The Fatigue Severity Score significantly decreased in ED (Hedges' g=0.63) and CT (Hedges' g=0.82) from pre to post, but not in C. Breathlessness and lower body strength improved most in CT. Significant within-group improvements in HRQoL and the number of PCS symptoms occurred in all groups.

Conclusions: Both exercise regimes led to increases in VO2peak and lower fatigue scores in subjects with PCS. Improvements in HRQoL occurred in all groups, however more pronounced after the exercise interventions. No definite conclusion about the superiority of either training modality can be drawn.

Clinical Rehabilitation Impact: The results show that in this population both exercise regimes are feasible and safe and lead to improvements in various health domains.