Amino Acids and Exercise in FSHD

Inclusion Criteria: 1. Subjects of both sexes with a diagnosis of FSHD, confirmed by genetic testing. 2. Age between 18 and 50 years. 3. Belonging to clinical category A among the four defined in the Comprehensive Clinical Evaluation Form. These patients present the most characteristic signs of the disease: muscle weakness of the facial and scapular girdle. 4. Clinical score ranging from 2 to 5. 5. Preserved ability to walk at the time of enrollment. 6. Absence of central or peripheral nervous system involvement based on neurological history and physical examination. 7. Absence of scoliosis, limb contractures, and tendon retractions. Exclusion Criteria: 1. Use of beta-blocker medications; 2. Psychological or psychiatric disorders; 3. Musculoskeletal injuries that impair the ability to perform physical exercise; 4. Recent medication adjustment, use of drugs that may affect fatigue, or use of fatigue-stimulating agents (e.g., Modafinil, amantadine); 5. Ongoing participation in another clinical investigation involving a medical device or drug, or participation in such a study completed less than 30 days prior; 6. Pregnant or breastfeeding women; 7. Patients unable to understand the purpose and conditions of the study and unable to provide informed consent; 8. Presence of additional diseases that may interfere with measurements; 9. Patients deprived of liberty or under legal guardianship. Healthy participants will be age- and sex-matched adults without neuromuscular disease: 1. no chronic disease; 2. no neuromuscular disorders; 3. Same age range.