Anthony Joshua's training regime has been questioned by Joseph Parker ahead of their title unification fight in Cardiff on 31 March.

Joshua (20-0) will put his WBA, IBF and IBO heavyweight titles on the line against WBO title-holder Parker (24-0) in their highly-anticipated boxing clash.

Both unbeaten heavyweights will be looking to add titles to their collections as a win will take them closer to becoming the first champion to hold all major heavyweight belts. The winner of the clash would
only require Deontay Wilder's WBC title to become the ultimate champion.

While Joshua is the favourite heading into the fight, the Briton is also known to tire out in the latter rounds of his fights due to the muscle he carries.

Watching training footage of his strength and conditioning workouts, Parker is perplexed as to how stamina is still an issue for "AJ". He noted that he can fight hard through all 12 rounds and has even gone the distance in four of his last six fights.

"My body type, even though it's not really muscular, [has] worked for us," Parker told Sky Sports. "We know that we can fight hard from round one to round 12. It's all that matters.

"When you watch him, when you see all the training, it's like they are doing all this new training and it looks really hard, and it looks intense, and it looks the type of training that will prepare you for 12 rounds.

"But, in saying that, just maybe their team need to work on a few things. We know that our team has a good structure and a good training programme that will allow us to fight 12 rounds, if we need it. But I'm not sure why he tires, that's something he has to sort of figure out."

It's a sentiment that is echoed by Parker's coach, Kevin Barry, who has warned Joshua that he should be prepared to face an onslaught from the New Zealander in the latter rounds.

"I see videos posted everywhere of him doing the most sophisticated, new-age training methods that man has ever seen and, yet he's looked very tired in his last couple of fights," Barry explained.

"Every time he's been asked to go on to the later rounds, he's really struggled so that's a question for his training staff. He wouldn't want to be slowing against Joe, because I can promise you this. Joe will be coming on in the later rounds."