I use a heavy resistance cable I got from Target (5 feet long with handles) for most of the BR workouts. It was fine--until I got to Workout 5. The third circuit of that one is just evil. I've done the program for 4 rounds already, and I think that one, along with the first circuit of Workout 7, are the two most challenging in the entire program. So I also got the light resistance cable just for Workout 5 so I could actually do the moves.