Anthony Joshua unveiled a more athletic and less musclebound physique before warning Andy Ruiz Jr that their rematch will be "a marathon not a sprint".
Joshua's hint at dragging his conqueror into the later rounds will be put to the test on Sunday, live on Main Event, with ring-walks from about 6.30am (AEST).
"Away from the bright lights of the media after I took my loss, it was a time to reflect and that's what I did," Joshua told Sky Sports.
"The changes I've made will make it very difficult for Ruiz Jr in the rematch. Everyone talks about change but us fighters have a spark in us. I fine-tuned.
"It's a marathon not a sprint, and I will be victorious. The main thing is about being in control of every situation.
"I know how good I am. I dedicate my life to boxing so it will be no surprise when I win. This is all I've got so when I do amazing things I keep my head on my shoulders, and my feet on the ground. I know I'm capable of doing it but it's about doing it in those 36 minutes."
Former champion Joshua was unshaven with longer hair and looked noticeably slimmer during Tuesday's public workout in Saudi Arabia, as the intensity of the week continues to build towards the world heavyweight title rematch.
Asked if he would be lighter than the 112kg he weighed-in before losing to Ruiz Jr, Joshua explained: "I would be three months in the gym, three months promoting. This time I spent six months in the gym and that's why you see a boxer's lean physique."
Boxing pundit Dave Coldwell said Joshua looked "slender and sleek". "He looks built for speed and mobility. The elasticity of his muscles looks better. We will see a faster and better-balanced AJ. I think he's under 108kg."
Former pro Spencer Oliver added: "I've known him since he was 18 and he looks slimmer now than he was before the Olympics. The only reason to come in light is, I believe, to stick and move. Not sit in the pocket."
Ruiz Jr has no concerns about Joshua's slimmer physique and has vowed to once again "prove everyone wrong."
"I don't think it'll matter, I'll weigh the same I did on June 1," Ruiz Jr told Sky Sports.
"I know 'AJ' has been working on different technicals, he's slimmed down, so we've been working on different things and angles, different pressures and combos, ready for whatever he brings.
"I didn't want to do anything different. We just trained harder and focused more in the gym on the speed and the technicals, and of course the pressure."
Ruiz Jr knows that he will once more have people doubting his champion credentials but is determined to "make another dream come true."
"Every boxer has to have that confidence that they are better than other fighters. I don't underestimate anyone in the ring, I know AJ will look good, it's my job to prove everyone wrong again," he said.
"I've been working hard since I was six-years old, these belts mean a lot to me. I made my dreams come true and now I'll make another dream come true."
Joshua's promoter Eddie Hearn insisted another defeat would not damage his man's career beyond repair.
"Win, lose or draw he has a future," Hearn said. "If he loses this fight? He will have had 24 fights, lost to one man, and unified the division twice.
"He will box in 2020, he will box in 2021, and he will probably box in '22 and '23."