Ever since the United States Anti-Doping Agency (USADA) partnered with Ultimate Fighting Championship (UFC), it's really done a number on plenty of fighters on the roster.
While the agency has been cracking down on performance-enhancing drug (PED) users, the controversial IV ban has caught a bit of flack from some fighters.
Coincidentally enough, after Penn was flagged for violating said ban because he admitted to using an IV under a doctor's supervision, USADA released an explanatory note detailing exactly why it's no longer allowed.
WHAT'S THE IV RULE?