Trevor Wittman (born March 5, 1974) is an American boxing and mixed martial arts coach.
[3] Compelled to retire from boxing at 21 years old after being diagnosed with a hyperinflated lung, Wittman transitioned to training boxers in the Denver metropolitan area.
[7] The business broadened its scope to include other combat sports such as mixed martial arts, eventually resulting in Wittman closing T's K.O.
Fight Club[8] and establishing the Grudge Training Center facility[5] in Wheat Ridge in 2009.
To focus more attention on ONX Sports, Wittman closed down Grudge in November 2016, though he continues to train a few select fighters, including Rose Namajunas, Justin Gaethje, and Kamaru Usman.