Impact of eccentric exercise on walking functional capacity after severe COVID-19: randomized, controlled open-label trial

INTRODUCTION: Severe COVID-19 infection leads to profound pulmonary, cardiovascular, and neuromuscular impairments, resulting in marked exercise deconditioning and reduced functional walking capacity after hospital discharge. Eccentric cycling offers high mechanical load with low metabolic cost and may therefore represent a relevant rehabilitation strategy to restore functional capacity in people after COVID-19. AIM: To compare functional recovery after 8 weeks of eccentric (ECC) or concentric (CON) training in individuals discharged 1 month previously after a COVID-19 infection. METHODS AND ANALYSIS: The CovExc trial was a multicenter, randomized, controlled, open-label study conducted in 3 centers. Adults (<80 years) at least 1 month after hospital discharge for severe COVID-19 were randomized (1:1) to 8 weeks of ECC or concentric CON ergometer training (3 30-min sessions per week). The primary outcome was change in the 6-minute walk test (6MWT) distance between baseline and post-intervention (M2). Secondary outcomes included physical performance, muscle strength (handgrip), fatigue, and quality of life. Analyses were conducted in the modified intention-to-treat (mITT) population using mixed models. RESULTS: Of the 60 participants enrolled, 56 (median age (IQR): 54.5 (48; 62)) were included in the modified intention-to-treat population, including 33 men (59%). Forty-four participants completed the program. Intergroup analysis showed no significant differences between the ECC and CON for any variable. However, within-group analyses of the primary endpoint (mITT and per-protocol) revealed a significant change between baseline and 2 months (P = 0.002 and P = 0.001 for ECC and CON groups on mITT and P = 0.001 for ECC and CON groups on per-protocol). 6MWT improved by 18 m in ECC (0; 72) and 28 m in CON (0; 53) (median difference -10 m; 95% CI (-42 to 22). CONCLUSION: Both eccentric and concentric training improved walking distance in participants after COVID-19, with no difference between groups. Further randomized controlled trials are needed to confirm the effectiveness of these approaches for people who survived COVID-19. TRIAL REGISTRATION: NCT04649086.