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 type of muscle fibers would be most useful to you. Correct A

Slow-twitch muscle fibers, also known as type I, have low power but high endurance capabilities.  They contract more slowly and less forcefully than the fast-twitch muscle fibers (Type II). They are most useful for marathon runners because they are teeming with mitochondria, myoglobin and capillaries which are ingredients that ensure the steady supply of oxygen and energy we need to run aerobically.