Type I fibers, so-called slow twitch muscle fibers, are well known to be difficult to fatigue and to have weak occurrence tension.
In VI, the percentage of Type I fibers was significantly higher than that of Type II fibers (P < 0.01).
However, the percentage of Type I fibers is significantly higher than Type II fibers in AG (P < 0.01).
reported that VI has 47[+ or -] % of Type I fibers and 53[+ or -]3 % of Type II fibers.
Type I fibers were not found in the pectoralis major muscle of the RBC and HW quail lines.
Cross-sectional area of type IIB fiber is generally larger, as the growth rate of type IIB fiber after birth is approximately two times greater compared to type I fiber (Oksbjerg et al., 1994).
At a depth of 20mm, type IIA and IIX fibers, showed similar F which were significantly higher than that of type I fibers (Table 1) in the non-exercises horses.
The effect of light physical exercise on the F of different types of muscle fibers at a depth of 20mm, was evaluated and there was a significant decrease in type I fibers (P=0.048), a significant increase in type IIA fibers (P=0.012), and no effect on type IIX fibers.
After training, at a depth of 20mm, showed that the CSA of type IIX fibers was significantly greater than the CSA of type I fibers and similar to the CSA of type IIA fibers.
However, in comparing the CSA of fibers at a depth of 60mm, type IIX fibers showed a significantly greater CSA, followed by type IIA fibers and type I fibers. When the effect of the biopsy depth on CSA for the three types of fibers was examined in non-exercised horses, no difference was observed.