In response to the criticism, the UFC increased cooperation with state athletic commissions and redesigned its rules to remove the less palatable elements of fights while retaining the core elements of striking and grappling . UFC 12 saw the introduction of weight classes and the banning of fish-hooking . For UFC 14 , gloves became mandatory, while kicks to the head of a downed opponent were banned. UFC 15 saw limitations on hair pulling, and the banning of strikes to the back of the neck and head, headbutting, small-joint manipulations, and groin strikes. With five-minute rounds introduced at UFC 21 , the UFC gradually re-branded itself as a sport rather than a spectacle.