With “Just Dance,” I am elevating my heart rate, but I am also sidestepping the self. Depending on the song and background images, I am a partying hipster in a floor-length fur (Macklemore, “Can’t Hold Us”), or a futuristic funk dancer (Nicki Minaj, “Pound the Alarm”), or a girl with swinging blond hair at a club. Critics complain that the offerings on “Just Dance” skew painfully toward bubble-gum pop, but it also means that on “Just Dance,” I am forever young.