Importantly, loss of dystrophin and reduction of fast MHC resulted in reduced twitch tension (−35 ± 7% at 100 Hz tetanus, n = 8, P < 0.05) and prolonged contraction and relaxation times demonstrating that ESM culture unmasks early changes of DMD myopathy (Figure8E,F). This evidence concerns the gene DMD and Duchenne muscular dystrophy.