Reality TV star Brody Jenner did what 14 actors and professional athletes couldn’t, at least not this time around: pass Special Forces: World’s Toughest Test.

The Hills alum and influencer Kayla Nicole were the only two of the 16 celebs competing to triumph on Wednesday’s third season finale of the Fox show. Ex-Special Forces operatives led the recruits, as they’re called, through a punishing series of exercises designed to push them to their limits. This go round, audiences saw them being buried alive, interrogated by the enemy for hours, running mercilessly, and jumping off a bridge.

But he tells EW that instead of celebrating, he found himself recovering.

“As soon as I left the show, I was really ill for two weeks, just in bed eating, trying to just nurse my health back,” he explains. “I was in rough shape after. I lost a bunch of weight. And it’s a rough experience to put your body through, for sure.”

Jenner believes it was a task they did on the sixth or seventh of 10 days that did him in. They had to jump into a trough of water and then do bear crawls in dirt, which Jenner remembered as “one of those hard fitness tests that they did at nighttime.”

“[NFL player] Cam [Newton] and everybody else had been washing all their dirty gear in that water for days and days and days,” Jenner says. “I mean, that water, when you walked by it … you could smell that water. It was disgusting.”

He didn’t react well physically.

“I woke up, my eyes were sealed shut. My throat was just on fire, and I got really sick for the remainder of the show,” Jenner says. “So all of a sudden I came down [with something], but I didn’t complain. I banged it out, and luckily it didn’t move into my lungs until after I left. So it was really in my sinuses and in my face, and I just got through it. And then when I left, my body was really able to just get sick. I think the adrenaline and wanting to make it to the end kind of suppressed the sickness.”

As the season has aired, Jenner has been watching it live, while staying in touch with the cast.

“I think that when you go through an experience like that with people, with anybody, you have this bond that you have for the rest of your life,” he notes. “We still talk. We have a group chat. We all talk on there, and yeah, I still keep in contact with pretty much all of ’em.”

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One thing he’s seen on playback is himself being vulnerable as the DS (Directing Staff) ask him questions meant to test him, about topics such as his relationship with his family, including parent Caitlyn Jenner. It’s a side of the younger Jenner that viewers don’t always see.

“When I signed up, I had watched the previous seasons. I know that they get you in that room and they become human, and they bring these things out of you,” Jenner explains. “And to be honest, you’re in a very vulnerable state…. You’re not sleeping. You’re getting so physically exhausted. You’re kind of out of it. And then when you get into the room with these guys, the DS, and they really become human all of a sudden, I mean, you want to just release things. It’s weird. It is just things come out without you even knowing.”

For him, Special Forces doesn’t compare to any other reality show.

“They call it the world’s toughest test for a reason,” Jenner says. “It is so incredibly physically and mentally grueling, and the thing is, you don’t win anything at the end besides something for yourself. I mean, there’s no prize at the end. You can essentially get paid to do the show and leave the first day, and you still get your money. I mean, there’s no incentive to make all the way to the end unless you want something for yourself, and you want to be there, and you want to go through this experience.”