Gruesome footage of powerlifter Robyn Machado snapping her arm while squatting 369 pounds has gone viral.

Machado picked up the injury in March 2020, but footage of the incident has re-emerged after the powerlifter made a TikTok video explaining what happened.

In the shocking TikTok clip, which is taken at a competition, Machado is seen lifting the bar and preparing for the deep squat.

As she begins to lower herself with three spotters around her, there is a cracking sound and her left arm snaps.

Machado revealed she broke her radius bone, an injury which needed a plate and eight screws put in her arm.

TikTok users reacted in horror to the clip, with one commenting: "The pop gave me goosebumps and I had to look away."

Another wrote: "Omg your scream gave me chills", while a third person commented: "This is why I don’t work out".

The 35-year-old was also accused of being "too weak" to squat 369 pounds, and "stupid" for attempting it.

In response, Machado posted a video of herself squatting 375 pounds, 380 pounds and 386 pounds.

She also explained in a TikTok why her attempt at 369 pounds had gone so wrong.

"The first thing that went wrong was the day before when you go in and they take your weight and rack heights and stuff, the squat rack had the bench in between and I'm short," she said.

"I had to straddle a bench while trying to get my squat rack height. Honestly that was ridiculous."

Machado continued: "So the next day at the meet I did my first squat and it was fabulous... then my second attempt squat – the 369 that I tried – I'm like 'I could do that in my sleep'... my one rep max, at the time, was at least 405 so I thought I was good.

"I got under the bar and I noticed it felt a little bit higher and I though 'you know what, this has happened to me many times, I'll be fine' plus I had so much adrenaline going."

Machado revealed she had to go on her tiptoes to get the bar over the hook.

"It hit the hook on the left side and started to kind of roll," she said. "But again, this has happened in the past, I've been squatting this way for four years.

"I start to go down and I feel the bar slide even further. It was a brand new bar... I felt the pressure on my arm and I heard that loud crunch.

"I looked over and could see - not the bone - but the bone popping from underneath the skin and I just screamed."