User blog comment:PitchBlack696/Zinogre/@comment-114.120.23.87-20101228170614/@comment-2040723-20110105151831

It also activates when you've taken a total of 200 damage from any source- whichever comes first. If you cart before the boost expires, the timer resets so you either need to fight for 5 more minutes or take 200 more damage.