This is a 48-week open-label extension of our initial proof-of-concept study (UCD0113) in patients with Becker muscular dystrophy who participated in the earlier trial. This single center study will enroll up to 10 adults who will receive the purified nutritional extract (-)-epicatechin 100mg/day orally for 8 weeks. After screening visits, participants will be enrolled in the study if they meet all inclusion criteria. They will be evaluated at screening, baseline, and weeks 4, 8, 12, 24, 16 and 48. The main criterion for success of the study will be presence of one or more biologic or strength and performance outcome measures that yield a response magnitude that allows for sufficient power in a Phase II B study with a sample size of 30 individuals.