Effects of Sodium Nitrate on Blood Flow in Becker Muscular Dystrophy

There are 2 phases to this research project: (1) an initial baseline study to confirm the blood flow abnormality in Becker muscular dystrophy, and (2) a subsequent brief treatment trial. There are also 3 optional study protocols: (A) dose-escalation trial, (B) placebo trial, and (C) increased exercise intensity trial. The baseline study involves an intake history, physical examination, and phlebotomy for blood chemistries and DNA followed by non-invasive forearm blood flow studies (Near Infrared Spectroscopy, Doppler Ultrasound) before and after a brief bout of handgrip exercise (approximately 3-5 hours to complete). Blood flow studies will be performed with the subject's lower body enclosed in an airtight chamber. Blood flow and oxygen delivery to the forearm muscles will be measured before and during application of lower body negative pressure at rest and during handgrip exercise. Lower body negative pressure simulates the blood flow changes that normally occur when a person sits up after lying down. The results of the baseline study will determine which patients meet preset eligibility criteria to participate in the medication phase of the study. These criteria include (1) normal kidney and liver function tests and normal BNP levels (the latter to exclude heart failure), and (2) abnormal blood flow responses to handgrip exercise. Eligible patients will be asked to repeat the above laboratory procedures on a subsequent study day after receiving a single dose of sodium nitrate. Eligible patients will also be offered the option to repeat the above laboratory procedures on three subsequent study visits, where upon: (A) the dose of sodium nitrate is increased, (B) a placebo is ingested, and/or (C) the level of exercise in increased. The investigators plan to enroll 20 adult men with Becker muscular dystrophy.