Avi broke his ankle skiing. At first, he felt a sharp and intense pain. The next day, the sharp pain was gone, but his ankle throbbed almost all the time. The sharp, immediate pain was due to ; the later, throbbing pain was due to .

fast fibers; slow fibers

Explanation:

Avi broke his ankle skiing. At first, he felt a sharp and intense pain. The next day, the sharp pain was gone, but his ankle throbbed almost all the time. The sharp, immediate pain was due to fast fibers; the later, throbbing pain was due to slow fibers.

There are two general types of skeletal muscle fibers: slow-twitch (type I) and fast-twitch (type II). Slow-twitch muscles help enable long-endurance feats such as distance running, rthereby causing pain to linger for a while, while fast-twitch muscles fatigue faster but are used in powerful bursts of movements like sprinting making pain fast and short in terms of length

answer; existed; limited;

answer; posthypnotic;