Final answer:
To maximize contraction speed in a muscle without considering force, the best fiber arrangement is fusiform, with fast twitch fibers being ideal due to their quick ATP hydrolysis and rapid cross-bridge cycling.
Step-by-step explanation:
If you want to design an ideal muscle that maximizes contraction speed without concern for the force produced, the best muscle fiber arrangement would be fusiform. This is because fibers in a fusiform muscle run parallel to the length of the muscle, thus allowing them to shorten much more than pennate muscles. In pennate muscles, such as unipennate, bipennate, and multipennate, the muscle fibers can only pull at an angle and do not move their tendons as far, which results in slower contraction speeds compared to fusiform muscles.
The speed of contraction in muscle fibers is influenced by how quickly myosin's ATPase hydrolyzes ATP for cross-bridge cycling. Fast twitch fibers, or fast glycolytic (FG) fibers, contract quickly as they hydrolyze ATP at a faster pace. Contrastingly, pennate muscles, despite allowing more muscle fibers to fit and produce greater tension, do not favor speed due to the angled arrangement of their fibers.