Lack of obscurin results in sarcolemma fragility after exercise. (A–D) Evans blue dye (EBD) was injected intraperitoneally 12 h before the last running session. Analysis of EBD uptake in tibialis anterior (A and C) and diaphragm (B and D) reveals that the obscurin KO condition results in sarcolemma fragility. A higher number of EBD-positive fibers was found in exercised obscurin KO muscles when compared with controls. Bar, 50 µm.