Inclusion Criteria  Men and women 70+ years of age OR men and women 18-50 years old Body mass index between 19 and 40 kg/m2. Willingness to undergo all testing procedures, maintain current diet during the study period, and adhere to the study protocol.  Exclusion Criteria:  Neuromuscular Disease (ie. movement disorder, or overt neurological disease, such as Sensory Neuropathy with Sensory Ataxia, Apraxia, Post-Polio Syndrome, Mitochondrial Myopathy, Myelopathy, myasthenia gravis) Neurological Disease (ie. Dementia (Alzheimers, multi-infarct, fronto-temporal); multiple sclerosis, amyotrophic lateral sclerosis, Parkinsons Disease, cerebellar ataxia, or significant cognitive impairment (a score of 22 or less on the Montreal Cognitive Assessment (MOCA)) Musculoskeletal disorders (ie. rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, acute gout or osteoarthritis limiting mobility) Terminal illness(i.e., Cancer, myeloma, acute leukaemia) Uncontrolled Psychiatric disorder (ie. bipolar, schizophrenia, major depression) Cardiovascular Diseases (ie. NYHA Class III or IV congestive heart failure, clinically significant aortic stenosis, recent history of cardiac arrest, uncontrolled atrial fibrillation, use of a cardiac defibrillator, or uncontrolled angina or hypertension) Other significant conditions (ie, that would impact safety and/or compliance to the protocol (e.g. chronic renal failure requiring peritoneal or hemodialysis, chronic liver disease, blood dyscrasia, carcinoma within last 3 years, severe inflammatory bowel disease, severe respiratory disease (uncontrolled asthma, COPD), etc) Drug or alcohol abuse Not meeting MRI eligibility (e.g. metal implants, reported pregnancy or positive pregnancy test at the time of imaging for women aged 55 years or younger); Not meeting the DEXA eligibility (e.g. reported pregnancy or positive pregnancy test at the time of imaging for women aged 55 years or younger); Failure to provide informed consent; Subjects who do not answer "male" or female" to the question of biological sex Currently or recently (within the last 1 year) taking gender affirming hormones.