Mass and cross-sectional area of EDL in C57, casp, mdx and mdx-casp mice. Mass (A and C) and calculated CSA (B and D; see Methods for details) of EDL muscles from C57, casp, mdx and mdx-casp mice aged 5 months (A and C) and 1 year (C and D). Bars represent mean ± standard error. *Significantly different from C57, ‡significantly different from casp and †significantly different from mdx by one-way ANOVA with Tukey's Multiple Comparison Test. n = 6–11 mice per genotype.