Grudge Training Center

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

 * Rose Namajunas 🇺🇸 – Former 2x UFC Women's Strawweight Champion
 * Nate Marquardt 🇺🇸 – UFC
 * Pat Barry 🇺🇸 – UFC
 * Justin Gaethje 🇺🇸 – UFC Former Interim Lightweight champion
 * Brandon Girtz 🇺🇸 – Bellator
 * Justin Salas 🇺🇸 – UFC
 * Luke Caudillo 🇺🇸 – Strikeforce, UFC
 * Tyler Stinson 🇺🇸 – Bellator, Strikeforce
 * Brandon Thatch 🇺🇸 – UFC
 * Justin Wren 🇺🇸 – Bellator
 * Shane Carwin 🇺🇸 – Former UFC Interim Heavyweight champion
 * Rashad Evans 🇺🇸 – UFC Hall of Famer
 * Duane Ludwig 🇺🇸 – UFC
 * Ed Herman 🇺🇸 – UFC
 * Todd Duffee 🇺🇸 – UFC
 * Melvin Guillard 🇺🇸 – UFC
 * Brendan Schaub 🇺🇸 – runner-up on The Ultimate Fighter: Heavyweights
 * Jon Jones 🇺🇸 – UFC Former Light-Heavyweight Champion
 * Gerald Harris 🇺🇸 – WSOF
 * John Howard 🇺🇸 – UFC
 * Jared Hamman 🇺🇸 – UFC
 * Tyler Toner 🇺🇸 – UFC
 * James McSweeney 🇺🇸 – UFC
 * Paul Buentello 🇺🇸 – Bellator, Shark Fights
 * Cody Donovan 🇺🇸 – UFC
 * Eliot Marshall 🇺🇸 – UFC
 * Alvin Robinson 🇺🇸 – UFC


 * 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