A young Australian mixed martial arts (MMA) fighter has died from a rare health condition linked to intense gym workouts.

Jake Sendler, 21, from Melbourne, died weeks after collapsing during a bout at an MMA event in the inner city earlier this month.

He was found to have a life-threatening condition known as rhabdomyolysis triggered by severe muscle breakdown that floods the body with harmful toxins, his family said.

While preparing for the bout, Sendler unknowingly pushed through worsening symptoms. He continued training, working and coaching, unaware that his body was shutting down.

On leaving the ring, his condition rapidly deteriorated, leading to emergency hospitalisation and multiple organ failure.

His doctors said it was the most severe case of rhabdomyolysis they had ever encountered.

To help Sendler’s shattered family, a  GoFundMe page has been set up in memory of him and has raised more than $30,000 in just a few hours.

“Fighter, Coach, Warrior – His Legacy Lives On,” it read.

“With profound sadness, we share the heartbreaking news that Jake has passed away. Jake was not only a fighter in the MMA ring but also a true warrior in life.

“A dedicated athlete, compassionate coach, beloved son, brother, and friend, Jake’s generous heart, boundless energy, and unwavering support deeply touched everyone who knew him.”

Sendler was making his debut at the Road to Hex 3 fight night in Kensington on Sunday, March 3 when he was tragically injured, according to News Corp.

He was spotted wildly throwing punches “at the air” during the final round of his three round fight.

Hex Fight Series MMA Promotions has been contacted by 9news.com.au for comment.