Skeletal Muscle Damage in COVID-19: A Call for Action

Abstract

Both laboratory investigations and body composition quantification measures (e.g., computed tomography, CT) portray muscle loss in symptomatic Coronavirus disease 2019 (COVID-19) patients. Muscle loss is associated with a poor prognosis of the disease. The exact mechanism of muscle damage in COVID-19 patients, as well as the long-term consequences of muscle injury in disease survivors, are unclear. The current review briefly summarizes the literature for mechanisms, assessment measures, and interventions relevant to skeletal muscle insult in COVID-19 patients. Muscle injury is likely to be attributed to the cytokine storm, disease severity, malnutrition, prolonged physical inactivity during intensive care unit (ICU) stays, mechanical ventilation, and myotoxic drugs (e.g., dexamethasone). It has been assessed by imaging and non-imaging techniques (e.g., CT and electromyography), physical performance tests (e.g., six-minute walk test), anthropometric measures (e.g., calf circumference), and biomarkers of muscle dystrophy (e.g., creatine kinase). Interventions directed toward minimizing muscle loss among COVID-19 patients are lacking. However, limited evidence shows that respiratory rehabilitation improves respiratory function, muscle strength, quality of life, and anxiety symptoms in recovering older COVID-19 patients. Neuromuscular electrical stimulation may restore muscle condition in ICU-admitted patients, albeit empirical evidence is needed. Given the contribution of malnutrition to disease severity and muscle damage, providing proper nutritional management for emaciated patients may be one of the key issues to achieve a better prognosis and prevent the after-effects of the disease. Considerable attention to longer-term consequences of muscle injury in recovering COVID-19 patients is necessary.

Keywords: COVID-19; aging; coronavirus disease 2019; cytokine storm; intensive care unit-acquired weakness; malnutrition; musculoskeletal; myoglobin; older adults; rhabdomyolysis; severity; skeletal muscle.

Figure 1

Possible factors contributing to skeletal muscle injury in Coronavirus disease 2019 (COVID-19) patients. Abbreviations: SARS-CoV-2: severe acute respiratory syndrome-coronavirus-2, ICU: intensive care unit. Catabolic molecules released in individuals with baseline sarcopenia and obesity usually occurring in older adults and comorbid conditions, secondary to inflammaging and malnutrition, along with the cytokine storms induced by SARS-CoV-2, may directly injure muscular structures. Energy imbalance associated with gastrointestinal symptoms, muscle deconditioning by prolonged bed rest, myotoxic drugs such as dexamethasone, deficient nutrition, the cytokine storm, and mechanical ventilation contribute to ICU-acquired weakness among critical COVID-19 patients.