Code-hopping superstar Sonny Bill Williams has shown off a new training program that's left his high performance managers stunned.

Sonny Bill Williams has been out of the rugby league arena since 2014, but it hasn’t taken long for him to find his footing in the sport again.

The 34-year-old former All Blacks and Kiwis representative has immediately impressed his new Toronto Wolfpack coach Brian McDermott ahead of the upcoming English Super League season, the NZ Herald reports.

McDermott has hailed Williams as a “training freak” and has credited the team’s multimillion-dollar signing for his work ethic since arriving in the team’s English-based camp this week.

“He’s come back in great shape,” McDermott said of Williams, who last saw action in November during the bronze medal match at the Rugby World Cup in Japan.

“The guy’s a training freak, anyway, a gym freak. You can’t keep him out of the gym. He looks good.”

Williams trained with the team for the first time on Friday morning in the first training season to involve overseas talent.

“It’s been a good day, it’s been an enjoyable day,” McDermott told the Canadian Press.

“First time the whole group’s been together since the grand final last year.”

It’s no surprise Williams has arrived in tip-top shape after he recently showed off a new training program that left his high performance managers stunned.

Williams was in Kingscliff, on the northern coast of NSW, earlier this summer conducting his own pre-season training camp ahead of his high-profile move to Toronto on a two-year, $10 million deal and he was leaving no stone unturned ahead of his Super League debut.

Nine News Sydney reported at the start of December he had been conducting a “torturous training camp” at the Surfing Australia high performance centre to get his body in peak condition.

High performance coach Michael Crisp said Williams’ unique training regimen is designed to protect the former All Blacks star’s body and give him the best chance possible of remaining injury free when he’s still playing professional football at the age of 36 in Toronto.

“He’s amazing.” Crisp said. “He’s 34. 110 kilos. He’s like three humans.”

Williams’ has been working with former Roosters strength and conditioning guru Keegan Smith, the son of former Roosters coach Brian Smith. Smith said Williams’ training camp was unlike anything he is aware of previously being used to train rugby league athletes.

“The kind of training that we’re doing, I don’t think any player’s ever actually done to prepare themselves for footy,” Smith said.

“That opens up the possibility of getting some results that haven’t been seen as well. So we’re excited.”

The Wolfpack, who won promotion to the top division at the end of their 2019 campaign, kick off their Super League season February 2 against Castleford Tigers.

Their first home game isn’t until April 18 against Hull FC.

With NZ Herald