Mechanical properties of type I and type IIB single porcine muscle fibres

Single muscle fibres were isolated from longissimus dorsi (LD) and vastus intermedius muscles at 1 or 8 days post-mortem. Fibres were classified as type I or IIB and their mechanical properties determined. In LD day 1, individual type IIB fibres fractured at higher (P < 0.001) loads and lower (P < 0.001) stress values than type I fibres. The strength of type I fibres did not differ between muscles. Storage for 8 days decreased (P < 0.001) breaking stress of type I fibres, whereas the breaking stress of type IIB fibres did not change. In conclusion, type IIB fibres were weaker per cross-sectional area than type I fibres in LD. The mechanical properties of type I fibres did not differ between muscles and the change in strength with post-mortem storage were more marked in type I than in type IIB fibres.