Effects of massaging on hardness, rheological properties, and structure of four wild boar muscles of different fibre type content and age

Histochemistry (percentage number of three type fibres and their cross-sectional area) and changes in hardness, rheological properties (elastic and viscous moduli), and structural elements (mean fibre cross-sectional area and thickness of endomysium) of four wild boar muscles of different ages: biceps femoris (BF), semimembranosus (SM), quadriceps femoris (QF), and longissimus (L) subjected to effective massaging for 1, 2, 3, and 4 h were evaluated. BF, with the high percentage of type I fibres, higher mean fibre cross-sectional area, thicker endomysium as compared with QF, SM and L, was harder, more elastic, and more viscous than the other three muscles. Muscles of older boars were found to contain higher percentages of type I fibres, lower percentages of type IIB fibres, bigger muscle fibre cross-sectional areas, thicker endomysium and higher values of hardness than the same muscles of young boars, whereas the percentage of type IIA fibres was about the same in the muscles of both groups. No effect of age on rheological properties was found. Muscle massaging resulted in an increase in the mean fibre cross-sectional area, changes in thickness of the endomysium, reduction in hardness and viscous moduli as well as in the elastic moduli of the muscles studied. The lower the initial values of textural and structural parameters and percentage of type I fibres of a muscle were, the higher was the muscles susceptibility to massage. BF compared to SM, QF and L, of all the older boar muscles tested compared to those obtained from young boars were less susceptible to mechanical tenderization.