No effect of low-intensity endurance exercise on muscle necrosis in the diaphragm of mdx mice.

Duchenne muscular dystrophy (DMD) is characterized by progressive skeletal muscle weakness. We havepreviously shown that low-intensity endurance training prevented muscle damage (Frinchi et al, Int J Sports Med2014). Since the effects of low-intensity endurance training on the the diaphragm in the mdx mouse model areunknown, in the same animals we investigated C x39 protein levels (Western blotting) in homogenates of thediaphragm before and after training. Mdx and wild-type (WT) mice were randomly assigned to sedentary (mdx-S,n=17; WT-S, n=19) or trained (mdx-EX, n=14; WT-EX, n=16) groups. Low-intensity endurance training (running ona wheel) was done 5 days/week for 6 weeks at progressively increasing time (15 min to 1 h) and speed (rpm from16 to 24, distance covered during training sessions from 48 to 288 m). C ompared to our previous analysis ofskeletal muscles changes in gastrocnemius and quadriceps, showing decreased muscle damage in trained vssedentary mdx mice, analysis of protein level of C x39 showed similar values in diaphragm homogenates fromsedentary and trained mdx mice.These preliminary data suggest that prevention of muscle necrosis after mild training does not occur in thediaphragm. As a speculation, continuous work of diaphragm vs intermittent work of skeletal muscle might at leastpartly account for the different results obtained in respiratory and locomotor muscle.