Types of skeletal muscle fibers

The skeletal muscle fibers are classified mainly into two types:

1. Red (type I) fibers

2. White (type II) fibers

Red fibers are slow twitch fibers, i.e. their speed of contraction is slow but more sustained. They are fatigue resistant and hence largely present in postural muscles, long muscles of the back (antigravity muscles).

White fibers are fast twitch fibers, i.e., their speed of contraction is fast but less sustained. They are easily fatigued and hence largely present in extraocular muscles of the eyeball.

快收缩纤维以无氧代谢供能为主,输出功率大且易疲劳;慢收缩纤维以有氧代谢供能为主,输出功率小且具有较强的抵抗疲劳的能力。慢肌亦称"慢红肌"。肌纤维的一种。其特征是收缩慢,能持久。