Interventions Against Fatigue in Patients With Myasthenia Gravis

Inclusion Criteria: 1. Age ≥ 18 years 2. A clinical diagnosis of myasthenia gravis (ocular or generalized) as defined by the Dutch national guideline (category "definite" or "probable" MG). 3. The diagnosis of MG was made at least a year ago and the MG is stable, as determined by the treating neurologist. 4. Patients who use the following medication: prednisone, intravenous immunoglobulin (IVIg), complement inhibitor (e.g. Eculizumab), neonatal Fc receptor (FcRn) inhibitor (e.g. Efgartigimod) have been on a stable dosing regimen for at least one month. 5. MGFA Clinical Classification of disease severity I-IV. 6. Clinically relevant fatigue (a score ≥ 27 on the CIS-fatigue). 7. Ability to walk and exercise. 8. Ability to understand the requirements of the study and provide written informed consent. Exclusion Criteria: 1. The patient is unable to fill out the study questionnaires or be interviewed in Dutch, or is unable to undergo the tests needed for the study, or is unable to give informed consent for participation in the study. 2. The patient is unable to use the activity tracker and digital infrastructure provided. 3. Co-morbidity interfering with AET or affecting exercise response and exercise capacity, including severe cardiopulmonary co-morbidity, as assessed by the investigator. 4. Co-morbidity interfering with CBT, a clinical diagnosis of depression or a score ≥12 on the Hospital Anxiety and Depression Scale (HADS) depression subscale, as assessed by the investigator. 5. Use of beta blockers. 6. The patient is already engaged in strenuous exercise more than twice a week. 7. The patient is already undergoing cognitive behavioural therapy. 8. Pregnancy or intention to become pregnant during the study. Exclusion Criterion for muscle MRI 1. Inability to undergo MRI. \- In case of uncertainty about the MRI-contraindications, the MR-safety commission of the Radiology department will decide whether this subject can be included in the study or not.