Dressed in a traditional Cossack outfit for Wednesday's head-to-head press conference, the unified world champion remained on stage after he had faced off with Joshua to sing 'Oi u luzi chervona kalyna'.
The 1875 call to arms was inspired by Ukraine's 18th century battle for independence and is now intoned as a display of defiance in the face of Russia's invasion.
Usyk served as a military volunteer in Kiev before being told he would better represent his nation by successfully defending the WBA, IBF and WBO titles he seized from Joshua almost a year ago.
The rivals collide in Jeddah on Saturday and the undefeated 35-year-old has told Joshua to expect more punishment from his fists.
"We learned a lot about each other in the first fight. He learned about me and I learned about him," Usyk said.
"But this is not going to be a new bout, it's going to be the last bout continued for rounds 13,14,15 - for however long it lasts.
"We've had enough time to study each other and Saturday will be a great, great fight.
"We were born to compete at life, for belts, for anything. The one who does not compete, does not live.
"All our lives are competitions - for anything, for someone - that's why we're competing."