ABSTRACT
Post-COVID Syndrome (PCS) refers to a diverse array of symptoms that persist beyond 3 months of the acute phase of a SARS-CoV-2 infection. The most frequent symptom is fatigue, which can manifest both mentally and physically. In this study, handgrip strength (HGS) parameters were determined as an objective measure of muscle fatigue and fatigability. HGS parameters were correlated with other fre-quent symptoms among 144 female PCS patients suffering from fatigue, exertional intolerance, and cognitive impairment. Seventy-eight patients met the Canadian Consensus Criteria (CCC) for post-infectious myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). The severity of disa-bility and key symptoms were evaluated utilizing self-reported questionnaires. Notably, patients di-agnosed with ME/CFS exhibited a higher overall severity of symptoms, including lower physical func-tion (p < 0.001), a greater degree of disability (p < 0.001), more severe fatigue (p < 0.001), post-exertional malaise (p < 0.001), and autonomic dysfunction (p = 0.004). While HGS was similarly impaired in both PCS and ME/CFS patients, the associations between HGS and the severity of symptoms and disability revealed striking differences. We observed significant correlations of HGS parameters with physical function across all patients, but with the key symptoms PEM, fatigue, cog-nitive impairment, and autonomic dysfunction in ME/CFS patients only. This points to a common mechanism for these symptoms in the ME/CFS subtype, distinct from that in other types of PCS. Further HGS provides an objective marker of disease severity in ME/CFS.