Anthony Joshua was at a career-high 115kg for his last fight and has worked hard with trainer Rob McCracken to reduce that for his clash with Joseph Parker.

Joseph Parker's camp have questioned the impact of Anthony Joshua's weight loss as the battle of the scales preludes the world heavyweight title fight.

Both boxers have been shedding kilograms in a bid to be at optimum fitness and performance levels for their April 1 (NZT) showdown in Cardiff where Parker's WBO title goes on the line alongside Joshua's IBF and WBA belts.

Neither camp have said what their weights were when they started their rigorous training camps, but have targeted significant differences from their last fighting weights.

Parker was 112kg when he laboured to victory over Hughie Fury and wants to come in around 107-108kg this time. Joshua was at a career-high 115kg against Carlos Takam and is eyeing 112kg.

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GETTY IMAGES Joseph Parker has conceded he was too heavy when he fought Hughie Fury in his UKL debut last September.

But Joshua suggested to the BBC he may have lost as much as 6kg. He likened it to "not having to run around with the equivalent of two new-born babies on his back".

The difference is in what sort of weight they are losing.

Parker certainly needed to shed his summer excesses on top of where he was at for Fury. But the perpetually-buffed Joshua is a different beast with little fat to lose.

DUCO Kiwi heavyweight Joseph Parker trains at former world champion David Haye's London gym.

"Is he shedding muscle and with that is there a reduction in power?" Parker's promoter David Higgins cheekily chipped before he hopped on a plan on Tuesday night bound for London.

Both fighters appear significantly leaner as they taper their training.

Higgins said Parker's improved shape hadn't been lost on their opposition.

"I spoke to Eddie Hearn on Monday night and he said, 'gee your man looks good, what's he weighing at? He looks sharp," Higgins said.

"Eddie also added, 'we know we are in a real fight'. That's because the bookies and fans have written Joseph off."

Ready for London 💥 #TeamParker A post shared by Joseph Parker (@joeboxerparker) on Mar 15, 2018 at 9:42pm PDT

Joshua dodged the issue of his weight when it was raised in an interview with host broadcaster Sky Sports UK on Wednesday.

"I'm not going to say because, last time I said that, I came in at my career-heaviest," he said when asked if he would be lighter.

"I'm not going to jinx it. Whether I'm bigger than I was for Takam, or lighter than I was for Dominic Breazeale, I will make sure I am victorious.

"I think stretching is important. Because I'm already a big guy I can tense up, naturally. I tend to do a lot more stretching now, to keep my body loose. I'm not snacking as much, which is something heavyweights can do."

Joshua has been accused of being muscle-bound with arguments that his gym fixation has hampered his movement inside the ropes.

Parker's quest to get back to the sort of weight that led him to winning the WBO world title in late 2016 is an admittance that they got things wrong last year.

Knowing Parker was inevitably going to fight bigger opponents like Joshua, there was a concerted effort to add size and muscle to the Kiwi-Samoan.

But the trade-off was a loss of speed, both with his footwork and deadly hands, two assets that set him apart among the new generation of heavyweights.

Paker has promised to be in the best shape of his career for his biggest challenge and says he is happy with his speed and movement in the gym.

Takam, the only common opponent that the unbeaten duo of Joshua and Parker share, sees the fight as a question of power versus speed.

"Joseph Parker, the guy has speed, a lot of speed. I think his speed is faster than Joshua," Takam told Sky Sports UK.

"Joshua is strong, but Parker's speed is faster than Joshua and we're going to see what is going to happen in the fight - speed or strength.

"For me, those two are the best. I have respect for Parker, I have respect for Joshua. For me, they are two good fighters, two good boxers, two good champions."

One thing is for sure, the weigh-in in Cardiff on the eve of the fight is going to have added significance when each fighter reveals their shape and weight as they stand on the scales.