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Muscle fatigue in patients with severe long COVID: A 2‐year follow‐up study

Year: 2026

Type: article

Abstract: BACKGROUND: Fatigue is recognized as one of the most persistent and debilitating symptoms of long COVID, affecting both functionality and quality of life. However, its long-term effects, especially beyond the first year after infection, remain poorly understood. OBJECTIVE: To investigate self-reported fatigue and muscle fatigability in individuals with severe long COVID compared to matched healthy controls at 18 and 24 months post infection. DESIGN: Longitudinal observational study. SETTING: The study was conducted at the Laboratory of Muscle and Tendon Plasticity at the University of Brasília. PARTICIPANTS: Twenty survivors of severe-COVID and 20 age- and gender-matched controls underwent repeat assessments at 18 and 24 months following hospital discharge. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Perceived fatigue was measured using the Fatigue Severity Scale, functionality with the 30-second sit-to-stand test, muscular dimensions and quality assessment were evaluated through ultrasound-derived thickness and echogenicity, and muscle fatigability was assessed using torque, torque-time integral, and rate of force development. The generalized estimating equations method was used with "group" and "assessments" as factors, with the least significant difference test identifying specific differences. Chi-square test compared categorical variables. RESULTS: The severe-COVID group showed consistently poorer functional performance (mean difference: 2.65 [0.45-4.85], p = .018), higher perceived fatigue (2.25 [1.54-2.95], p < .001) and lower rate of force development (-103.68 [-177.22 to -30.13], p = .006) compared to controls. No significant differences were observed in muscle thickness or echogenicity between groups. CONCLUSION: Long COVID is associated with sustained fatigue, impaired neuromuscular function, and reduced physical performance up to 2 years after infection. These findings underscore the need for long-term, mechanism-based rehabilitation strategies targeting central fatigue and neuromuscular function. TRIAL REGISTRATION: NCT04961255.

Source: PM&R

DOI: 10.1002/pmrj.70165