The back and forth between former UFC middleweight champion  Sean Strickland and former Navy SEAL and endurance athlete  David Goggins began back in July.   Strickland posted a video to instagram challenging any Navy SEAL to come train with him.  ”I don’t think there’s one f**king Navy SEAL who could survive a week training with me,” Strickland said video.   A Navy SEAL took Strickland up on the offer and showed up to spar the top UFC middleweight contender.