Nicole Scherzinger says working with rapper will.i.am on his upcoming album 'Willpower' was exhausting.
The 34-year-old said the Black Eyed Peas member is always "always thinking and creating", reported The Daily Star.
"He's like a crazy ball of energy that just bounces off the walls. He's always thinking and creating," she said.
The 'X Factor' judge also said that she has worked with will.i.am on her own solo project.
"He executively produced pretty much everything I've done, up until now," Scherzinger said. The singer's latest single "Boomerang" reached number six on the UK singles chart earlier this month.