EDL and soleus (SOL) force frequency relationship in non-dystrophic and mdx animals. EDL muscles (A) from C57 mice fed low (⭘; n = 5), medium (■; n = 4) and high (⯅; n = 6) vitamin D enriched diets and mdx mice fed low (⭘, broken line; n = 6), medium (■, broken line; n = 6) and high (⯅, broken line; n = 5) vitamin D enriched diets. SOL muscles (B) from C57 mice fed low (⭘; n = 5), medium (■; n = 4) and high (⯅; n = 6) vitamin D enriched diets and mdx mice fed low (⭘, broken line; n = 6), medium (■, broken line; n = 6) and high (⯅, broken line; n = 5) vitamin D enriched diets. Symbols indicate: ^^^^ p < 0.0001 significant difference between C57 and mdx strains.