Inclusion Criteria:  The randomized crossover trial will be performed in on otherwise healthy subjects without diabetes mellitus, chronic kidney disease (CKD), preexisting cardiovascular disease or treatment with any vasoactive agent that might alter cardiovascular responses to exercise.  Exclusion Criteria:  history of cardiopulmonary disease or chronic kidney disease, treatment with antihypertensive medications, estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m2, (4) diabetes mellitus or other systemic illness,  (5) pregnancy, (6) hypersensitivity to sodium phosphate, (7) any history of substance abuse or current cigarette use, (8) any history of psychiatric illness, (9) history of active malignancy, (10) serum phosphorus < 2.4 or > 4.5 mg/dL.