Study Purpose: To assess the impact of nitrite supplements on mitochondrial respiration, with associated focus on mitochondrial energetics and muscle perfusion, and to complete preliminary analysis on clinical correlates. To be enrolled in this study, you must meet certain requirements. You may be eligible to participate if you meet the following criteria: Study Duration: 16-weeks Study Commitment: 9 Outpatient visits and weekly calls Age: ≥70 years old Sex: Male or Female Conditions/Eligibility: • Age ≥70 years • Sedentary • Clinically stable and without hospitalization or invasive cardiac procedure for 6 weeks Study Procedures: • 4 muscle biopsies • multiple blood draws • oral nitrite consumption (3 times a day) • exercise testing • questionnaires Compensation: $550