In a piece about Britney's LV residency at, Taffy Brodresser-Aker chatted with a member of Britney's managerial team, who finally admitted that there was no way humanly possible for her to sing and dance for an hour and a half:

"To put on the show that she puts on, it's virtually impossible to sing the entire time and do what she does," Adam Leber told me. "She's singing on every song, basically, when she has the ability to sing. There's no way you can dance for 90 minutes straight and sing the entire time."