LONDON: Anthony Joshua says he is going to favour brains over brawn for the defence of his World Boxing Association, International Boxing Federation and World Boxing Organisation heavyweight titles against Oleksandr Usyk.

The 31-year-old British pugilist is set to go toe to toe with the undefeated Ukrainian former undisputed cruiserweight world champion at the Tottenham Hotspur Stadium in London on September 25.

Joshua told Sky Sports bulking up for the bout lacked common sense.

"I'm looking trim for this fight," he said.

"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.

"I've learned how to condition my body for specific fights.

"I've been training like a 15-round fighter in this camp."

"What happens when I train that way? My body adapts and takes its natural form. This is the form it has taken."

Joshua to fight Usyk at Tottenham Stadium in September

Joshua (24 victories 1 defeat, 22KOs) claims he is focussing more on adopting a streetwise approach to combat the guile of Usyk (18-0, 13KOs), who has had just two fights since stepping up to the heavyweight division.

"I am sharpening the mind so that I can concentrate for the 12 rounds," said Joshua.

"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."

The defence against Usyk replaced a long-awaited unification title fight with fellow Briton Tyson Fury.

That contest was scuppered when a United States arbitrator ruled World Boxing Council champion Fury must defend his title against Deontay Wilder.