The Efficacy of Oral Mitoquinone (MitoQ) Supplementation for Improving Physiological in Middle-aged and Older Adults

Inclusion Criteria: * Women will be confirmed as postmenopausal (either natural or surgical) based on cessation of menses for \>1 year. * Ability to provide informed consent * Baseline brachial flow-mediated dilation (FMD) \< 6%Δ (rationale: non-invasive screening to ensure exclusion of subjects with exceptionally high baseline endothelial function. * Ability to perform motor and cognitive tests (e.g., can rise from a chair, walk for 2 min, climb 10 stairs) * Willing to accept random assignment to condition Exclusion Criteria: * Current smoking * Having past or present alcohol dependence or abuse, as defined by the American Psychiatry Association, Diagnostic and Statistical Manual of Mental Disorders * Body mass index (BMI) \>40 kg/m2 (FMD measurements can be inaccurate in severely obese patients) * Chronic clinical diseases (e.g., coronary artery/peripheral artery/cerebrovascular diseases, diabetes, chronic kidney disease requiring dialysis, neurological disorders or diseases that may affect motor/cognitive functions \[multiple sclerosis, Parkinson's disease, polio, Alzheimer's disease, dementia or other brain diseases of aging\]), except hypertension and hyperlipidemia * Regular vigorous aerobic/endurance exercise (\>3 vigorous bouts/week). * Not weight stable in the prior 3 months (\>2 kg weight change) or unwilling to remain weight stable throughout study (rationale: recent weight change or weight loss can influence vascular function. * Current treatment or recent cessation (\< 3 mo) of hormone replacement therapy * Moderate or severe peripheral artery disease (ankle-brachial index \<0.7). * A graded exercise test will be performed by all subjects, if there is physician concern or an adverse event, the subject will not participate in a maximal oxygen consumption (VO2max) test (this will be determined in accordance with stated contraindications for exercise testing provided by the American Heart Association). * Thyroid disease that is not controlled by medications or \<3 month's use of a particular medication and/or dosage (uncontrolled thyroid diseases are associated with alterations in vascular function).