The star was cast as the historical gladiator earlier this year (11) after Spartacus: Blood and Sand actor Andy Whitfield was forced to step down to undergo treatment for cancer.

McIntyre steps into Whitfield's shoes for the second season of the U.S. series, now titled Spartacus: Vengeance, but he admits he almost lost out on the role because he was not the buff warrior TV bosses had envisioned when he auditioned.

Speaking on U.S. news show Access Hollywood Live, his co-star, Manu Bennett, says, "I had to screen test him. He was emaciated. But his eyes and his intention were fantastic... but (everybody was like), 'His body is wasted.'"

However, McIntyre was determined to pack on the pounds to win the coveted role.

He says, "I had to work out non-stop. I lost 20 kilograms (for a film), which in pounds, is (like) 45 pounds, it's like a fifth of my body weight or something. And then I had to put it all back on, plus muscle, and that was just non-stop training."