Final answer:
Skeletal muscle fibers can be categorized into slow-twitch and fast-twitch fibers, which differ in their contraction speed and ATP production. Slow-twitch fibers contract slowly and use aerobic respiration, while fast-twitch fibers contract quickly and primarily use anaerobic glycolysis. Most skeletal muscles contain both types of fiber, but the proportions differ.
Step-by-step explanation:
Skeletal muscle fibers can be divided into two types: slow-twitch (type I) muscle fibers and fast-twitch (type II) muscle fibers. Slow-twitch fibers contract relatively slowly and primarily use aerobic respiration to produce ATP.
Fast-twitch fibers have fast contractions and primarily use anaerobic glycolysis to produce ATP. Most skeletal muscles in a human contain both types of fibers, although the proportions vary.