Heat Therapy, Functional Capacity, and Vascular Health in Older Adults

Inclusion Criteria: 1. 55 to 80 years of age 2. No tobacco/nicotine use within preceding 6 months (e.g., cigarettes, chewing tobacco, nicotine gum or patches, and vapor smoking) 3. Systolic blood pressure \<140 mmHg; diastolic blood pressure \<90 mmHg 4. Normal 12-lead ECG (reviewed by a physician) 5. Normal clinical results from a medical exam reviewed by a board-certified physician (e.g., General Health Questionnaire - see attached document) 6. Body mass index (BMI) \<40 unless athletic/muscular build; calculation = body weight (kg)/height (m2) 7. Females Only: Post-menopausal Exclusion Criteria: 1. Not meeting the age criteria 2. Body mass index (BMI) \>40 unless athletic/muscular build; calculation = body weight (kg)/height (m2) 3. Use of tobacco or nicotine products within the last 6 months (tobacco cigarettes, chewing tobacco, nicotine patches or gum) 4. Not abstaining from the following 24 hours prior to the experimental session: exercise, alcoholic substances, prescription or non-prescription medications (unless cleared by the medical screener), dietary supplements, herbal medications, caffeinated substances (including chocolate, coffee, tea (iced or hot), caffeinated energy drinks, and sodas) 5. S who weigh less than 80 lbs 6. Use of prescription drugs, non-prescription drugs or herbal medicines known to alter vascular function unless cleared prior to the study 7. Use of anti-hypertensive medications 8. Use of beta blockers 9. Daily use of bronchodilators 10. Current use of anti-coagulant therapy 11. Current use of hormone replacement therapy (e.g., estrogen, testosterone) 12. Current diagnosis of cancer 13. Signs of overt cardio-metabolic abnormalities (e.g., uncontrolled diabetes - HbA1c \>7.5, a resting systolic blood pressure \>140mmHg or diastolic blood pressure \>90mmHg; abnormal 12-lead ECG) 14. History of cerebrovascular abnormalities (e.g., prior stroke, transient ischemic attacks, epilepsy, increased intracranial pressure) 15. Known history of atherosclerosis (i.e., plaque formation) 16. Autonomic dysfunction (e.g., Shy-Drager Syndrome, Bradbury-Eggleston syndrome, idiopathic orthostatic hypotension) 17. Respiratory illnesses (e.g., chronic asthma (including exercise-induced asthma), Chronic Obstructive Pulmonary Disease, Reactive Airway Disease). Note: subjects with exercised-induced asthma or who have had COVID-19 will be allowed to participate 18. History of anaphylaxis 19. Severe phobia of needles 20. History of alcohol or drug abuse which inhibits the participants ability to complete this study 21. Latex allergy 22. Known allergies or sensitivities to drugs used in the study (e.g., Lidocaine HCL, acetylcholine HCL, methacholine chloride, sodium nitroprusside, nitroglycerin, or related drugs) 23. Implanted electronic medical devices (e.g. cardiac pacemaker) 24. Tissue or skin abnormalities of the legs (e.g., infection, injury, open wound, ischemic tissue, phlebitis, active bleeding, neuropathy) 25. Tissue or skin abnormalities of the arm (e.g., unhealed or open wound or circulatory deficits) 26. Current Fever (oral temp \>99.5 °F/ 37.5 °C) aa) Current use of PDE3 inhibitors (e.g., Viagra) or soluble guanylate cyclase (sGC) stimulators (e.g., riociguat), or unwillingness to withhold medication for 2 weeks prior to laboratory testing bb) Diagnosis of neurological disease or cognitive dysfunction cc) Cardiac surgery or cardiac events (e.g., coronary artery bypass graft surgery, myocardial infarction, heart failure) dd) Abnormal clotting, clots in deep veins in the legs or pelvis, or blood clots to the lungs ee) Individuals who have had mastectomies ff) History of methemoglobinemia