Anthony Joshua has described the lengths he has gone to in order to prepare for his title defence against Oleksandr Usyk.
The 31-year-old Briton will put his IBF, WBA and WBO belts on the line against the Ukrainian at Tottenham Hotspur Stadium on September 25.
Speaking to Sky Sports, Joshua said: "Deep practice is where I put myself on the edge, where I am vulnerable, so I can improve.
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"I don't always want to be the best in the gym.
"Every time I spar, I spar like I'm performing. I have had tough spars. I am doubting myself.
"Throughout this training camp with southpaws I have practised, practised, practised. I am comfortable where my development is."
Joshua is not expecting anything different from Usyk despite his cruiserweight history, explaining: "All boxers can move up in weight. Some feel better at the higher weight, they carry more power and feel fresher.
"In my mind, I have removed the conversation that he is a cruiserweight.
"I get it. But I like to challenge myself. So I move it out of the way. Let's look at where I'm at skillswise and technique-wise. I've got what I already have - the strength.
"Since I came into boxing in 2008 I had a rapid rise, maybe due to sheer strength, size, heart. I took on massive challenges early on.
"Usyk is another great champion, great fighter. But I don't really fold under pressure.
"This is fun. This is deep practice. When I get into the ring it's time to practise everything I know.
"I'm rather experienced now. You have to go through trials and tribulations."