Final answer:
Fast-twitch muscle fibers are skeletal muscle cells specialized for quick and powerful contractions, suitable for anaerobic activities like weight lifting and sprinting, but fatigue quickly due to reliance on anaerobic glycolysis for ATP production.
Step-by-step explanation:
The muscle fiber that is referred to as fast-twitch muscle fiber is a type of skeletal muscle cell that is primarily responsible for anaerobic activities such as weight lifting and sprinting. These fibers, classified as fast glycolytic (FG) fibers, contract quickly and powerfully but fatigue rapidly because they rely on anaerobic glycolysis to produce ATP.
Fast-twitch fibers contain fewer capillaries, mitochondria, and myoglobin compared to their counterpart, the slow-twitch muscle fibers, which are better suited for aerobics and endurance activities like long-distance running.
Within the skeletal muscles, the composition of slow-twitch and fast-twitch fibers varies, contributing to our ability to perform different types of physical activities. Fast-twitch fibers have the capacity for a high force output, making them crucial in activities that require quick, powerful bursts of energy.
The speed of contraction in these fibers is contingent on the rapid hydrolysis of ATP by the enzyme myosin ATPase, facilitating quick cross-bridge cycling and muscle contraction.