. >> i'm at ballet arts, the performing arts center of southern westchester, and i'm here to learn about irish step dancing, so let's step inside. [ irish music playing ] irish step dancing has become increasingly popular all across the country. if you're not doing it yourself, chances are you've met someone who is. it's easy to identify. essentially, the upper part of your body remains motionless while your legs do all the work. >> it's a very precise art form. our biggest rule in irish step dancing would be arms by your side in all solo dancing. >> at first glance, it looks pretty simple, but, like most things in life, there's more to it than meets the eye. so we came to class to find out what it takes to be good. >> irish step dancing is a pretty peppy art form, so you wants lots and lots of energy, smiles, and always remember, arms by your side. >> the origin of "arms by your side" seems to be a mystery. some say it allowed people to dance in small spaces. others say on small stages. still others say it was the result of a restrictive government or a religious doctrine. >> arms in! >