Investigating Loss of Neuromuscular Junction Transmission Fidelity in Older Adults

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.