Post-Acute Sequelae of SARS-CoV-2 Infections: Exercise Limitation and Rehabilitation.

Patients with prior SARS-CoV-2 infections can develop chronic symptoms; this clinical presentation has been called post-acute sequelae of SARS-CoV-2 infection, post-COVID condition, and long COVID. It can develop in both outpatient cases and in hospital cases; the frequency depends on the severity of infection and comorbidity. Many of these patients have exercise limitation when tested using cardiopulmonary exercise tests. The potential explanations for reduced exercise capacity include cardiac limitations, respiratory limitations, skeletal muscle weakness, deconditioning, and limiting symptoms out of proportion to any measured physiological limitation, and many patients have more than one explanation for the exercise limitation. Since these patients may have required prolonged hospitalization, deconditioning has been considered a potential explanation for their post-hospitalization limitations. Patients with deconditioning have a low oxygen uptake per minute (VO₂) maximum with no obvious cardiac or respiratory limitation, but some do have measurable muscle weakness. One complex study reported that these patients had a high proportion of high-fatigable glycolytic fibers, reduced mitochondrial function, atrophic fibers, and focal necrosis in skeletal muscle. Some post-COVID patients have chronic fatigue and post-exertional malaise and meet the clinical criteria for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Most patients with post-COVID syndrome do improve with conventional cardiopulmonary rehabilitation. However, patients with post-exertional malaise need special attention to their exercise programs and careful monitoring for adverse effects. In summary, patients with long COVID can have complex presentations with a broad range of symptoms and several possible exercise limitations. Their rehabilitation program should be based on their physical capacity and their symptom profile.