The Ukrainian joined the military following Russia’s invasion of his home country, admitting he did not want to then leave before eventually being persuaded to do so to begin his training camp at the end of March.
He now returns to the ring this weekend to face Joshua once again, 11 months on from comprehensively beating the Brit in London to become unified heavyweight world champion.
Much of the focus of Usyk’s camp appears to have been on bulking up, potentially putting on as much as 15kg, and the 35-year-old is confident his body is ready for what is likely to be a far more aggressive Joshua on Saturday night in Saudi Arabia.
“In the first month of the war I lost 10 pounds,” Usyk told the Guardian.
“But when I started preparing for this fight I quickly gained the weight and my team put in all this incredible work to strengthen my body. I don’t want to say a lot about the weight but the main thing is I feel incredibly fit and strong.”
He added: “The whole time has been really tough. I don’t want anyone to pity me but the toughest time was at the beginning of the war because I wasn’t with my family.
“Not being with my wife and children is the toughest for me. But I got through this because I prayed to God and I felt confident again.”
This weekend’s fight will be broadcast free to those in Ukraine. Usyk intended to buy the TV rights in his home country to ensure the bout was available to all who wanted to watch, but a deal was reached with the Saudi organisers meaning he did not need to do so.
Usyk is also involved with a number of initiatives to raise money for those back in Ukraine, and he intends to give them something to celebrate by defending his belts against Joshua.
“I want to help my people and my country and Saturday night is going to be a small party for them, maybe a big party,” Usyk told Sky Sports.
“I will do my best to give the best performance that I can.”