Grudge Training Center (GTC) was a mixed martial arts training center founded by coach Trevor Wittman in 2009. Originally located in Wheat Ridge, Colorado, GTC relocated to Arvada, Colorado in 2013. The gym was an affiliate of Jackson's Submission Fighting. Wittman closed Grudge in November 2016.
Notable fighters
Notable and recurring trainees under Trevor Wittman
Stipe Miocic – UFC Former Heavyweight Champion
Neil Magny – UFC
Donald Cerrone – UFC
Georges St-Pierre – Former UFC Welterweight & Middleweight Champion