Cognitive, Psychological, and Physical Functioning in Long-COVID Patients With Different Levels of Fatigue.

Inclusion Criteria: The participant must report current persisting symptoms (such as brain fog, anxiety, shortness of breath, headaches but also others) and indicate on the Post COVID-19 Functional Status Scale that these have an impact on everyday functioning (grade 2, 3, and 4). These symptoms need to be present for more than two months. Further inclusion criteria are: * Fatigue Severity Scale (FSS) score \> 4 * Aged over 18 years old * Willing to sign the digital informed consent * Dutch speaking and Dutch understanding * Be tested positive for COVID-19, i.e. by reverse transcription polymerase chain reaction (RT-PCR), computed tomography (CT) of the lungs, or symptom-based diagnosis by the general practitioner. Exclusion Criteria: * Pregnant women * Pacemaker, defibrillator * Brain or nerve disorders * Epilepsy * A copper spiral or recent bone fracture