dave divas, there's now a class to give you buns. i took a booty blast class. at david barton gym. what is the perfect butt, half moon or bump? >> you want to strike a balance between the half-moon, the nice rounded and the way it goes into the hamstring is important. >> reporter: the fitness manager says forget cardio, the focus strength training. >> should we have a fear of bulking up. >> it is a misnomer. you will get more caloric expenditure more than you would with cardio. >> reporter: this butt burning class scorches 500 calories. >> drive your hips forward. squeeze your glutes. >> reporter: he says the key to gorgeous glutes is after burn. that's what strength training gives us. metabolism in high gear for 48 hours. >> back to reverse lunge. >> reporter: we kicked off with reverse lunges. >> see your butt. look at the master. a good half moon i'd say. >> i feel like a piece of meat.