Extensor digitorum longus (EDL) and soleus (SOL) absolute and specific force production in non-dystrophic and mdx animals. Absolute tetanic force (A) and specific force (B) of the EDL muscle from C57 and mdx mice from low (open bar; n = 4–10), medium (red bar, n = 6–10) and high (black bar; n = 6–10) vitamin D enriched diets. SOL absolute (C) and specific force (D) from C57 and mdx mice from low (open bar; n = 6–10), medium (red bar, n = 6–10) and high (black bar; n = 6–10) vitamin D enriched diets. Symbols indicate: * p < 0.05, significantly different to low diet. ^^^^ p < 0.0001, significantly different to C57 strain.