If you were running a marathon, which type of muscle fibers would be most useful to you?
a.

slow-twitch
b.

fast-twitch, type i a
c.

intermediate-twitch, type ii b
d.

slow-intermediate twitch, type i b

If you were running a marathon, the slow-twitch muscle fibers would be most useful to you. Correct A Slow-twitch fibers are one of the two types of muscle fibers, the other type is fast switch muscle fibers. The slow-twitch fibers use oxygen for fuel and offer extended muscle contraction and high endurance, which is needed in a case of marathon. The fast-twitch fibers on the other hand are useful for sprinters.

answer(b) keep oxygenated and deoxygenated blood separate;