Skeletal muscle fibrosis, a key pathological feature in muscle disorders, is still inaccessible by NMR. In this study, we investigated the effects of diffuse muscle fibrosis on T2, natT1, and extracellular volume (ECV, estimated from muscle and plasma T1 pre and post-Gd injection). In order to reduce interfering effects with fibrosis, we developed a new non-dystrophic mouse model with increased muscle fibrosis, but limited levels of inflammation and no fat infiltration. A positive correlation between ECV and collagen content could be observed. Collagen content presented a weak positive correlation with T1, and a weak but significant negative correlation with T2.