Final answer:
Striated muscles contract rapidly with less force through efficient motor unit recruitment, fast ATP hydrolysis by myosin ATPase in fast fibers, and utilization of oxidative and glycolytic pathways for ATP production.
Step-by-step explanation:
The underlying mechanism that allows striated muscles, such as skeletal muscles, to contract rapidly when less force is required involves the process of motor unit recruitment and the rapid hydrolysis of ATP. When minimal force is needed, fewer motor units are activated, allowing the muscle to conserve energy and avoid fatigue. This process is efficient due to the neural control that dictates which and how many motor units are recruited at a given time.
The speed of muscle contraction is also influenced by how quickly the enzyme myosin ATPase can hydrolyze ATP. Fast fibers possess a version of myosin that can hydrolyze ATP more swiftly than slow fibers, resulting in a more rapid contraction. This rapid cycling of cross-bridges allows for the quick pulling of thin filaments towards the center of the sarcomeres, shortening them at a faster rate and producing a contraction with light force.
Moreover, the muscle fiber's primary metabolic pathway helps determine its fatigue resistance. Oxidative fibers can create more ATP through aerobic pathways, making them more resistant to fatigue than glycolytic fibers, which produce less ATP per cycle through anaerobic processes and thus fatigue more quickly.