Singer Beyonce Knowles performs during the 81st Academy Awards in Hollywood, California in this February 22, 2009 file photo.[Agencies]

NEW YORK – Beyonce says one of the toughest parts of summer tour has been condensing more than a decade's hits into a two-hour show. Judging from a recent photo shoot, figuring out how to perform them in Thierry Mugler's elaborate, over-the-top costumes is just as difficult.

Beyonce strutted gingerly in one such outfit, with a motorcycle handle-type top and flashing light at the center. But the camera brought out Sasha Fierce, her alter ego moving confidently in the outrageous getup and stiletto heels.

"I'm never gonna go on stage or do a video and not work until my feet are blistered, and until I'm basically, I can't walk any more," the giggly but exhausted entertainer said later. "I always give, and I do that because I know how lucky I am, to do my job."

In a recent interview, Beyonce — whose latest CD, "I Am ... Sasha Fierce," is double platinum — talked about concerts (her tour kicks off June 21 at Madison Square Garden) in the YouTube age, what she will fight fiercely for and why Etta James never had her worried.

AP: How will this tour be different from your 2007 "B'Day" tour?

Beyonce: It's going to be more emotional, because this album, "I Am," that portion was a lot more real and raw and more sensitive. ... The best part about this tour is I'm working with Thierry Mugler, who is an icon and a legend, and I've been a fan.

AP: Often snippets of concerts end up on the Internet. Is it frustrating not being able to surprise people anymore?

Beyonce: It's very frustrating now. ... It's great because people can get a little sneak peak and say, "Oh, I wanna come to the show" or "I don't wanna go to that show" (laughs), and I'm fans of people so I go on there and check it out too. But you put so much of your heart and time into the wardrobe ... it's kind of unfortunate that people can see the show months before you get into their city, but that's life.

AP: One YouTube video from your last tour showed you falling, getting up and continuing.

Beyonce: A lot of people with heart can see that I have heart, and I encourage other people to have that same strength and fight, and I definitely get tired, I definitely mess up, I definitely fall down stairs. I forget the words, sometimes, but that's just life. I guess the question is, what are you going to do after that? And I always get back up, and it just makes me even stronger.

AP: In your new movie "Obsessed," out on Friday, you play a wife who fights to protect her family. What is the hardest thing you ever fought for?

Beyonce: Everything that's worth anything you have to fight for. You have to fight in your relationships, I have to fight for my career, I have to fight to stay in shape, because I get tempted to eat good old chocolate (laughs), and all this stuff everybody loves. It's all a fight, but it's worth it.

AP: When you sang "At Last" for the Obamas at the inauguration ball, Etta James said some pretty harsh things about you but later said she was joking. Did you know she was joking?

Beyonce: I played Etta James (in last year's "Cadillac Records"), so I did my research, I read her book. I was not at all surprised. That's Etta. She's hilarious (laughs).

AP: Your sister Solange twitters all the time. Do you do it?

Beyonce: My sister is the Twitter queen. She told me about the twittering, but I don't get it, I feel like I'm getting really old. I'm like, what? I don't understand. Just call me.