Britney Spears suffers in order to create perfection -- in this case, enduring an intentionally filthy set and lots of dancing in heels for the 'Till the World Ends' video shoot.

The video features Spears in a studded leather jacket and knee-high boots, dancing and sweating with several dozen people in a grungy club. "The set was a little much," Spears admits to MTV in a behind-the-scenes interview. "It was just grimy and it was gross. It was disgusting sometimes."

Despite Britney's assertion ("I've done so many videos that I'm at the point where I genuinely want to enjoy myself"), the 'Till the World Ends' shoot provided her with plenty of moments of discomfort.

In one scene, Spears committed a fashion faux pas of the worst kind by replacing her sexy heeled boots with Ugg boots. She explained that she made the switch because her feet were killing her, and that particular scene was a close-up. "It wasn't a full-length shot, so a girl's [gotta be] about comfort," she says.

Later, Brit's request for a bathroom break was denied when director Ray Kay decided they had to push ahead and wrap up the shoot in 10 minutes. This was the first time Spears had teamed up with Kay, whose recent video work includes Willow's 'Whip My Hair,' Adam Lambert's 'For Your Entertainment,' and the Sean Kingston-Justin Bieber collaboration 'Eenie Meenie.'

We'll see how the final cut turns out when the 'Till the World Ends' video premieres later this week.

Watch Clips of Britney Spears' 'Till the World Ends' Video