This answer explains how the 5 forms of affliction are derived. I understand that on Yom Kippur, the Torah specifically says that we should afflict ourselves.
WHy are these 5 afflictions applied to Tish'a B'Av? Or, a reverse question, perhaps, why are they not applied to any of the other fast days except for Tish'a B'Av (and Yom Kippur, which was answered, already)?