From article...
"Ballroom dancing gives you a great all-over cardio workout, where you use your own body weight, similar to what you’d get from an intensive Pilates class. You spend a lot of time bending low and using your legs to push up onto your toes. So it’s an especially good workout for legs and buttocks."
http://www.bodyandsoul.com.au/fitness/fitness+az/benefits+of+ballroom+dancing,25033