Both eccentric and concentric training improve walking distance in severe COVID-19 survivors.Eccentric and concentric training similarly improve walking distance in severe COVID-19 survivors in the CovExc trial.
“Our study did not show that eccentric training is superior to concentric training for improving walking endurance in individuals who survived COVID-19. Both methods improved walking distance and can be considered useful post–COVID-19 rehabilitation methods,” the investigators said.
In the modified intention-to-treat (mITT) population, the median 6-minute walk test (6MWT) distance increased by 18 m in the eccentric group and 28 m in the concentric group from baseline to month 2 (M2), but the median difference between groups was not significant (–10 m; p=0.311). “The value corresponded to a relative increase of 5 percent in the eccentric group and a 3 percent increase in the concentric group,” they noted.
In the per-protocol (PP) analysis, the 6MWT distance increased by 30 m in the eccentric group and 35 m in the concentric group. The median between-group difference was also not significant (–5 m; p=0.489).
The results remained consistent after adjusting for covariates, including baseline 6MWT (<500 m: p=0.281; >500 m: p=0.486) and ICU admission (no: p=0.889; yes: p=0.098). [Ann Phys Rehabil Med 2026;69:102125]
However, the within-group analysis showed a significant change from baseline to M2 in both the mITT (eccentric: p=0.002; concentric: p=0.001) and PP cohorts (p=0.001 for both groups). “Clinically, the improvements in walking capacity were meaningful in both groups,” they said.
Three serious adverse events (AEs)—two in the eccentric group and one in the concentric group—led to withdrawal. Compared with the concentric group, the eccentric group had more patients with musculoskeletal pain/discomfort that disrupted sessions (n=8 vs 2), but both groups had similar rates of other events disrupting sessions (n=5 and 6).
Post–COVID-19 rehab imperative
Apart from the pulmonary sequalae of severe COVID-19, patients typically develop marked neuromuscular changes that lead to profound exercise deconditioning, the researchers noted. These limitations persist even after discharge and affect quality of life, highlighting the importance of post–COVID-19 rehabilitation. [F1000Res 2020;9:636] “Rehab in this context must address both resistance … and endurance training.”
Concentric exercise is a well-established modality for improving aerobic capacity and functional mobility. However, this method may be challenging for individuals with persistent dyspnoea, fatigue, or reduced metabolic tolerance after severe COVID-19. [J Frailty Sarcopenia Falls 2023;8:188-194; BMC Pulm Med 2022;22:278]
Eccentric training is a promising alternative, as it enables individuals with limited aerobic reserve to train at higher workloads without increasing physiological strain. This, in turn, promotes rapid gains in muscle mass, strength, and power and enhances neuromuscular efficiency, thereby improving tolerance to sustained walking efforts. [Front Physiol 2017;8:114; Respir Physiol Neurobiol 2020;276:103414]
Sixty ambulatory adults (median age 54 years, 59 percent men) who had recovered from severe COVID-19 and been discharged from the hospital for at least a month were randomized 1:1 to eccentric or concentric training. Of these, 56 were included in the mITT cohort, and 44 completed the programme. Participants in both groups did three 30-min sessions per week for 8 weeks. Overall adherence rate was high, with 78 percent of participants completing >20 sessions.
“[C]ontrary to our initial hypothesis, eccentric exercise did not prove superior to concentric training. The results suggest that the functional improvements in both groups were primarily driven by the shared aerobic component of the intervention rather than by a modality-specific effect,” the researchers said.
Further studies are thus warranted to identify the optimal rehab modalities for COVID-19 survivors, they concluded.