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.