A Minnesota bodybuilder landed in the hospital “in tears and straight agony” after his arms “blew up” after attempting a popular fitness challenge, which he says could have killed him.

Michael Congdon, 32, had begun doing the “Murph Challenge” last May. A former competitor in the World’s Strongest Man competition, the bodybuilder told the Daily Mail he thought it would be “less extreme” than powerlifting. However, halfway through the challenge, Congdon says he was “puking and delirious” — and his arms became inflamed, unable to bend.

Two days later, Congdon says he “looked like a balloon animal,” as his arms swelled like they were “inflated by a pump.” He was “in tears and straight agony,” Congdon says. His fiancée took him to the hospital, where blood tests determined he had “unreadable” levels of creatine, signaling he had developed rhabdomyolysis.

Rhabdomyolysis — or rhabado is “a rare muscle injury where your muscles break down,” the Cleveland Clinic explains, saying it’s “a life-threatening condition that can happen after an injury or excessive exercise without rest.” It causes “your muscles [to] break down (disintegrate), which leads to muscle death. When this happens, toxic components of your muscle fibers enter your circulation system and kidneys.”

Congdon recalls trying to wait it out. “I felt unsafe in my own body, like something was seriously wrong, but I thought. ‘I’ve never done this before, I’ll be fine,’ “ he told the outlet, saying that he “came in unprepared” for the challenge.

The “Murph Challenge” is a fundraising challenge, often associated with CrossFit, which calls it the Murph Hero Workout. Done in honor of late U.S. Navy SEAL Lt. Michael Murphy, the rigorous workout entails running a mile, then doing 100 pull-ups, 200 push-ups, 300 squats, before finishing with another one-mile run — all while wearing a weighted vest or body armor.

“I was really scared for my life. That moment alone terrified me so much that I rescinded any need to find any of my physical limits ever again,” Congdon says. “I’d never experienced that sort of pain in my life. It was uncontrollable shaking and crying because my body hurt so bad.” 

“Pushing myself to the max and almost dying was the final straw. I only do enough to feel good now,” Congdon tells the outlet. “I don’t train nearly as much, if at all. That was a truly life-changing, mind-changing moment.”

“I should have died.”

PEOPLE has reached out to CrossFit and Forged, which sponsors the Murph Challenge, for comment, and will update with further info.

Never miss a story — sign up for PEOPLE’s free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from celebrity news to compelling human interest stories.