Jumping Mechanography is a Suitable Complementary Method to Assess Motor Function in Ambulatory Boys with Duchenne Muscular Dystrophy.

OBJECTIVE: The number of clinical trials for Duchenne muscular dystrophy (DMD) has increased substantially lately, therefore appropriate clinical instruments are needed to measure disease progression and drug efficacy. Jumping mechanography is a medical diagnostic method for motion analysis, which allows to quantify physical parameters. In this study, we compared mechanography with timed function tests (TFTs). METHODS: 41 ambulatory DMD patients performed a total of 95 chair rising tests (CRT) and a total of 76 single two-legged jumps (S2LJ) on a mechanography ground reaction force platform. The results were correlated with a 6-minute walk test (6MWT) and the time required to run 10 meters, stand up from a supine position, and climb four stairs, all performed in the same setting. RESULTS: Our measurements show a high correlation between mechanography and the TFTs: S2LJ/10-m run, r = 0.62; CRT/10-m run, r = 0.61; S2LJ/standing up from supine, r = 0.48; CRT/standing up from supine, r = 0.58; S2LJ/climb four stairs, r = 0.55; CRT/climb four stairs, r = 0.51. The correlation between mechanography and the 6MWT was only moderate with r = 0.38 for S2LJ/6MWT and r = 0.39 for CRT/6MWT. INTERPRETATION: Jumping mechanography is a reliable additional method, which can be used for physical endpoint measurements in clinical trials. We confirmed our assumption, that the method provides additional information concerning performance at movement with higher power output. We suggest using the S2LJ as a first-choice tandem tool combined with the 6MWT. In patients with higher disability, the CRT is an alternative measuring method, because with the progression of the disease this is longer feasible.

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

OBJECTIVE: 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. PATIENTS AND METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Six-minute walk test versus two-minute walk test in children with Duchenne muscular dystrophy: Is more time more information?

BACKGROUND/PURPOSE: The six minute walk test is a widely accepted primary outcome parameter in most studies in Duchenne muscular dystrophy (DMD). To compare information obtained by the six minute walk distance (6MWD) test and the two minute walk distance (2MWD) in patients with DMD, a cohort of 13 voluntary DMD boys did a repeated six minute walking test. METHODS: Patients had to be ambulatory with a physical disability according to Levels 1-3 on the Vignos-Scale for lower extremity. Measurements were taken at one minute intervals. Reliability was measured by intraclass correlation. RESULTS: Test-retest reliability for 6MWD and 2MWD in two different age classes was very good for both subgroups. Test-retest-reliability was lower in patients with more advanced disability in both tests. Walking speed remained completely stable from time points 1-6 minutes in the whole study patient collective, which indicates that physical exhaustion is not reached after six minutes even in more disabled patients. CONCLUSION: Thus the 6MWD in DMD patients does not give additional information as compared to a 2MWD.