IBF, IBO, WBA, WBO heavyweight champion Anthony Joshua is taking every possible measure in his ongoing training camp, as he prepares for the mandatory defense against Oleksandr Usyk.

Their showdown will take place on September 25 from the Tottenham Hotspur Stadium in London.

Usyk, a former undisputed cruiserweight champion, is likely the best natural boxer that Joshua will face.

And Joshua admits that Usyk's boxing ability and movement will make him a very difficult opponent.

"100 percent, he will be. Movement means you are never stationery to get hit. Movement is important. Concentration - when you want to [punch], you lock in, then make a move. You have to make sure your brain works. That can be mentally fatiguing so I am sharpening the mind so that I can concentrate for the 12 rounds," Joshua said to Sky Sports.

"Also I practice having the ability to [punch] four times, not just once. It's a fight for the brain. Knowing what you've got in front of you and knowing how to deal with it. You can either be aggressive, corner [him], throw everything at it. Or take your time, be clever, then knock [him] out."

Joshua is not training for a knockout - and he's not training for size.

He wants to be quick with his punches and have the proper stamina to last the full distance.

"I'm looking trim for this fight. I'm fighting a guy who is a 12-round fighter. So it would be silly of me to go in there bulky with my muscles screaming for oxygen," Joshua said.

"I've been training like a 15-round fighter in this camp. I will be well-conditioned to fight. That is key. What happens when I train that way? My body adapts and takes its natural form. This is the form it has taken."