Résumé :
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Background: Clinically relevant outcome measures are necessary to monitor disease progression and to evaluate treatments in boys with Duchenne Muscular Dystrophy(DMD). Endurance is related to functioning in daily life and is, therefore, a clinically relevant outcome measure. However, the Six-Minute Walk Test (6MWT), which isthe current "gold standard" that assesses endurance, is not applicable for wheelchair-dependent boys. Therefore, we developed the Six-Minute (assisted) Bicycle Test(6MBT) for the legs and arms. The aims of this study were to examine the 1) feasibility, 2) construct validity, and 3) reproducibility of the 6MBT in healthy boys and boyswith DMD. Methods: Twenty-nine ambulatory or recently wheelchair-dependent boys with DMD (mean age 10 years) performed the 6MBT with the legs and arms. Fiveof them also performed the 6MWT. Eighty age-matched healthy boys performed both the 6MBT and 6MWT. A subgroup (n=10) performed the 6MBT twice in two weeks.The primary study outcomes were the number of revolutions (6MBT) and distance walked (6MWT). Secondary study outcomes were the heart rate, perceived exertionand surface EMG. Construct validity was examined using Pearson correlation coefficients. Reproducibility was calculated using the limits of agreements. Results: Allboys, both healthy and with DMD, were able to complete the 6MBT. The number of revolutions was higher in healthy boys (legs: mean 834, SD 78; arms: mean 773,SD 108) compared to boys with DMD (legs: mean 413, SD 145; arms: mean 362, SD 113) (p<.01). The 6MWT and 6MBT were positively correlated in healthy boys(legs: r=0.61, p<.01; arms: r=0.64, p<.01). The data of the reproducibility, and the secondary study outcomes, are currently being analyzed and will be presented at theconference Discussion: The 6MBT is a valid outcome measure to assess endurance and is able to discriminate between healthy boys and boys with DMD. The 6MBTis the first endurance test that can be performed by wheelchair-dependent boys with DMD. We recommend the implementation of the 6MBT in daily practice and futureclinical trials for the assessment of endurance in DMD patients.
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