Zac Efron has been having stem cell therapy to treat his injured back

Zac turned to Dr. Adeel Khan at Canada's Eterna Health clinic and will continue to receive treatment and has promised to keep fans updated on his progress.

He posted to Instagram: "I fully commit to my roles, which I love, but it takes a toll-my back was messed up after The Iron Claw, even after months of PT.

Curious about stem cell therapy, I reached out to @dr.akhan at @eterna.health who answered all my questions and made me feel confident.

"Now, six months post-treatment, I'm back in the gym and already seeing improvements.

"Excited to explore the latest longevity technologies through the Eterna Membership Program-I'll keep you updated on my progress! (sic)"

Zac previously admitted his determination to be in the right physical condition for the role turned into an "obsession" - but he admitted that helped him get into character.

He told The Rake magazine: "I have always admired physical transformations for a role and I have had a couple of goes at it.

"And one way or another none of them were perfected on any level.

"For Kevin, I knew that if I was going to do this right and hold my head high, it was going to be the most physically gruelling workout and diet regimen I had ever embarked on.

"I started training six months prior to filming. By the middle of the six months, I realised that that obsession with looking as good as possible and that dedication to the work and the food was becoming an obsession for me, and I took that into the role.

"It was a way for me to become Kevin in a way that I hadn't anticipated.

"We were both ultimately preparing for roles, as wrestling is a performance too."

Last month, Zac suffered a "minor" swimming accident whilst vacationing in Ibiza, which turned out to be a chest injury.

The 'Greatest Showman' star was pulled out of the water by two people working at the villa, before being hospitalised as a precautionary measure.