Is Exercise-Induced Fatigue a Problem in Children with Duchenne Muscular Dystrophy?

Duchenne muscular dystrophy (DMD) is a devastating X-linked muscular disorder. The number of studies investigating new therapeutic approaches is substantially increasing. This study aims to investigate the impact and diagnostic value of exercise-induced fatigue in DMD, which has been proposed as a suitable outcome parameter in other conditions like spinal muscular atrophy. A cohort of 55 DMD patients (49 of them treated with steroids and 9 with ataluren) underwent a total of 241 6MWT (mean 4.4 tests/patient) which were retrospectively analyzed. Exercise-induced fatigue was assessed by the ratio between the distance achieved in the sixth minute and the distance in the second minute of the 6MWT. In previous studies a quotient above 1 was defined as a sign of fatigue. The average fatigue quotient in the whole cohort of patients was 1.0. In a further analysis no impact of age, steroid therapy, ataluren therapy, overall disability, and distance in the 6-minute walk test (6MWT) on fatigue in DMD patients could be shown. Our data show that fatigue does not play a relevant role in DMD. Analysis of fatigue is not a useful outcome parameter in DMD studies. For this reason we suggest the 2MWT, which is better accepted by the patients, as an alternative to the commonly 6MWT.