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Myostatin (GDF8) and dystrophin are critical molecules for muscle organisation. Myostatin is involved in regulating muscle growth and development, whereas dystrophin is part of the dystrophin-glycoprotein complex (DGC), which anchors the cytoskeleton to the sarcolemma. We examined temporalis muscle morphology and function in myostatin deficient and dystrophin deficient (Mdx) mice in order to determine how myostatin and dystrophin affect bite force and muscle fibre composition. Bite forces from 4-month-old myostatin-/-, dystrophin deficient (Mdx) and normal control mice were measured by load cell and field stimulation of the temporalis muscle. Tissue sections were stained with haemotoxylin and eosin (H&E) and the periodic acid-Schiff reaction (PAS) to assess morphology and fibre type differences. A positive relationship between bite force and muscle mass for both genetic models was observed. Both Mstn-/- and Mdx mice showed significant elevation in bite force and muscle mass. Histological examination revealed greater muscle fibre cross-sectional area variability in Mdx mice (ANOVA, F=5.6, P