Net difference in change in 6-minute walk test from baseline to weeks 12; 26 and 52 (using random effects linear regression to account for repeated measurements)Timepoint: Week 12 26 and 52

Net difference in change in 6-minute walk test from baseline to weeks 12; 26 and 52 (using random effects linear regression to account for repeated measurements)Timepoint: Week 12 26 and 52