Repeated Hand Grip Strength is an Objective Marker for Disability and Severity of Key Symptoms in Post-COVID ME/CFS

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. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work is supported by a grant from the Weidenhammer-Zoebele Foundation. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was conducted in accordance with the Declaration of Helsinki, and approved by the Ethics Committee of the Charite - Universitaetsmedizin Berlin (EA2/066/20 from 08.04.2021 and EA2/067/20 from 27.04.2020). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes The data presented in this study are available on request from the corresponding author.