A, Representative micrographs (upper panel) of superficial tibialis anterior (TA) muscle stained for type IIA (green), type IIB (red), and type IIX (purple) myofibers in wild-type and transgenic mice. Quantification of different fiber types (lower panel) in superficial TA (N=8 mice). B, Representative micrographs (upper panel) of deep TA stained for different myofibers. Quantification of different fiber types (lower panel) in deep TA (N=8 mice). *Statistically significant difference between wild-type and transgenic mice (P≤0.001, unpaired Student t test). Scale, 100 µm.