Rehearsing for This Is It "Invigorated" Michael Jackson

Despite rumors that preparing for his 50-date final concert series fatally taxed a frail Michael Jackson, his choreographer insists that rehearsing the show had the opposite effect.

''I can tell you this experience, working on this show, was invigorating, was nourishing," says choreographer Kenny Ortega, "it wasn't taking away from Michael."'

But, Kenny — who's currently working on the Footloose remake with Chace Crawford in Kevin Bacon's role — had to keep an eye on the insomniac superstar.

''Michael had sleepless nights and we had to look after him," says Kenny says, "I'd say to him, 'Stay hydrated, have a protein shake - Did you eat today before you came?'''

Even if Michael claimed he had eaten, Kenny says he wouldn't necessarily believe him.

''Michael's an adult. We didn't want to baby him," he says, ''But I had concerns and we had conversations, wanting to make sure he was doing everything he could to build himself and not break himself down.''

Kenny has worked with Michael —who died of an accidental overdose aged 50 on June 25 — on world tours for the Dangerous and HIStory albums.

This Is It premieres on Oct. 28 and runs for just two weeks. A 12-minute preview clip show's Michael  warming up his vocals during a performance of "Human Nature".