Final answer:
Muscle fiber speed of contraction is influenced by the type of fiber and its metabolic pathways. Fast fibers use anaerobic glycolysis, which speeds up contraction but causes quick fatigue. Slow fibers use aerobic pathways, allowing them to sustain contractions for longer periods without significant fatigue.
Step-by-step explanation:
The type of muscle fiber and the metabolic pathways it uses determine how quickly it can contract. Rapid fibers cause faster contraction rates and cross-bridge cycling because they hydrolyze ATP more quickly. These fibers quickly tire because their primary source of ATP production is anaerobic glycolysis. Slow fibers, on the other hand, are better suited for endurance exercises since they mainly produce ATP through aerobic pathways, which increases their resistance to fatigue.