While the number of new treatment options tested in patients with Duchenne 
muscular dystrophy (DMD) is increasing, there is still no defining of the most 
reliable assessments regarding therapeutic efficacy. We present clinical and 
radiological outcome measures used in ambulatory patients participating in our 
trial "Treatment with L-citrulline and metformin in Duchenne muscular 
dystrophy". The motor function measure is a validated test in patients with 
neuromuscular disorders that consists of 32 items and assesses all three 
dimensions of motor performance including standing and transfer (D1 subscore), 
axial and proximal motor function (D2 subscore), and distal motor function (D3 
subscore). The test shows high intra- and inter-rater variability but only when 
strictly following guidelines of the materials, examination steps, and 
calculation of scores. The 6-minute walk test, timed 10-meter walk/run test, and 
supine-up time are commonly used timed functional tests that also sufficiently 
monitor changes in muscle function; however, they strongly depend on patient 
collaboration. Quantitative MRI is an objective and sensitive biomarker to 
detect subclinical changes, though the examination costs may be a reason for its 
limited use. In this study, a high correlation between all clinical assessments 
and quantitative MRI scans was found. The combinational use of these methods 
provides a better understanding about disease progression; however, longitudinal 
studies are needed to validate their reliability.