I also dont know.
But factor in not all dance numbers and choreography are the same. Some stuff is just going to put you out of breath no matter, its very physical. Britney and Beyonce and Madonna lip snyc because of their routines.
You can have a less physical performance and actually still sing.
True. This may not be the level of Madonna stage show but this 70 year old woman appears not to be lip syncing and is putting on a show in heels
https://www.youtube.com/watch?v=TTfYnRQgKgY