Final answer:
The speed of muscle contraction is influenced by the rate of ATP hydrolysis in myosin and the metabolic pathway used by the muscle fiber.
Step-by-step explanation:
The speed of contraction in muscle is determined by several factors. One key factor is how quickly myosin's ATPase hydrolyzes ATP to produce cross-bridge action. Fast muscle fibers have a higher rate of ATP hydrolysis compared to slow fibers, resulting in faster cross-bridge cycling and quicker contraction speed. Another factor is the primary metabolic pathway used by the muscle fiber, which determines whether the fiber is classified as oxidative or glycolytic. Oxidative fibers produce ATP through aerobic pathways and are more resistant to fatigue, while glycolytic fibers primarily rely on anaerobic glycolysis and fatigue more quickly.