Final answer:
Skeletal muscles usually contain a mixture of slow oxidative, fast oxidative, and fast glycolytic fibers, each with different contraction speeds and metabolism.
Step-by-step explanation:
Most skeletal muscles contain a mixture of fiber types, including slow oxidative (SO), fast oxidative (FO), and fast glycolytic (FG) fibers. These fiber types differ in contraction speed and their method of ATP production. Slow oxidative fibers contract relatively slowly and use aerobic respiration, while fast oxidative fibers contract quickly and primarily use aerobic respiration but can switch to anaerobic respiration. Fast glycolytic fibers also contract quickly but use anaerobic glycolysis, causing them to fatigue more rapidly.
Skeletal muscle fibers can be broadly classified into three main types based on the speed of contraction and ATP production: slow oxidative (SO), fast oxidative (FO), and fast glycolytic (FG) fibers. SO fibers contract slowly and primarily use aerobic respiration to produce ATP. FO fibers contract quickly and mainly use aerobic respiration as well, but can switch to anaerobic respiration. FG fibers contract rapidly and primarily use anaerobic glycolysis.