-putting only one foot in the band instead of both feet
-switching from easier to more difficult variations of the pull-up movement itself. For example one could start with chin-ups (which are generally considered less difficult than pull-ups because the biceps contribute more to the movement) and then employ pull-ups with the thumb wrapped around the bar. To make the pull-up more difficult one can refrain from wrapping the thumb around the bar in an opposing manner to the rest of the fingers and instead have the thumbs go over the top of the bar only just as the other fingers do. Apparently this will employ less bicep than the conventional pull-up and will thereofre isolate the back a little bit more.