Why does my back hurt after doing the move the hip hop move the swipe?

im in grade 7 and after doing the hip hop move the swipe my lower back always hurts. this is the move the swipe http://video.google.ca/videosearch?hl=en&source=hp&q=hip%20hop%20move%20the%20swipe%20video&um=1&ie=UTF-8&sa=N&tab=wv#