This article is an excerpt from a natural history study published in Neurology in 2025, focusing on the sensitivity of clinical outcome measures in assessing adult patients with Becker Muscular Dystrophy (BMD) over a three-year period. Researchers aimed to identify which functional tests, such as the Rise From Floor velocity (RFFv) and the North Star Ambulatory Assessment (NSAA), were most responsive to the disease's slow and variable progression for use in clinical trials. The study concluded that RFFv was the only measure with high responsiveness across the entire cohort at three years, although selecting a subgroup based on phenotype (NSAA scores 10–32) significantly improved the sensitivity of RFFv, NSAA, and 4-stair climb velocity earlier in the follow-up. Furthermore, the analysis suggested that genotype selection did not significantly enhance responsiveness, and the decline in cardiac function occurred independently of skeletal muscle function. Overall, the findings recommend the use of NSAA in clinical trials for ambulant BMD patients due to its broad feasibility and consistent decline, especially when patients are selected based on baseline NSAA scores.