Inclusion Criteria:  Age 75 or older SARC-F > 4 Decrease in muscle strength: grip strength <27 kg for men and <16 kg for women; and/or Chair stand test < 15 seconds Patient affiliated or beneficiary of a social security plan Patient who has signed informed consent beforehand  Exclusion Criteria:  Neurocognitive disorder preventing the expression of informed consent Lack of a measurement site (muscle resection or amputation) Impossibility or contraindication to strict dorsal and/or ventral decubitus Any associated neuromuscular pathology that may alter muscle composition and trophicity Wearing a pacemaker Any state of water inflation or dehydration History of surgery on the studied lower limb less than 6 months old Patients protected by law under guardianship or under curate, or unable to participate in a clinical study under Article L. 1121-16 of the French Code of Public Health