The goal of this observational study is to learn and assess muscle morphological and electromechanical properties in patients affected with Marfan syndrome (MFS) and Ehlers Danlos syndrome (EDS). the main questions it aims to answer are: * To assess the ability to develop muscle strength; * Muscle and tendon morphology involved in muscle contractions/relaxation; * Neuromuscular functionality. Participants will be take part in the study by performing a test for the assessment of the neuromuscular activity (voluntary muscle contractions) and undergoing a muscle ultrasound for the study of muscles and tendons. Researchers will compare the two groups with a control group to see potential differences in the morphological and neuromuscular structures of syndromic patients.