Abstract. BACKGROUND: The progressive weakness of Duchenne muscular dystrophy (DMD) interferes with performance. This study investigated the sensitivity to change and the responsiveness of sitting and standing from the ground in patients with DMD. AIM: The aim was to assess the sensitivity to change and the responsiveness of lowering to/ rising from the ground, in three, six, nine, and twelve month-evaluation intervals and to define the most suitable reevaluation intervals for ambulatory patients with DMD. METHOD: This is an observational, longitudinal study. Recordings of 28 patients performing lowering to/ rising from the ground were analyzed. Sensitivity to change was assessed using effect sizes and standardized response means. Responsiveness was assessed using minimal detectable changes (MDC) and minimal clinically important differences (MCID). RESULTS: In the lowering to the ground, significant sensitivity to change was found in higher than 6 months reassessment intervals. In the rising from the ground, significant sensitivity to change was observed in higher than 9 reassessment intervals. MDC and MCID varied from 1.0 to 1.6 points and from 0.5 to 2.5 seconds when lowering to the ground and from 1.3 to 2.6 points and from 5.0 to 28.0 seconds when rising from the ground. CONCLUSION: Patients should be reassessed after nine months from the lowering to and rising from the ground. Increments of 2.0 points and/or 2.5 seconds (or higher) in the score of lowering to the ground assessment denote clinically relevant changes. Increments of 3 points (or higher) in rising from the ground assessment are clinically relevant.