http://AskTheTrainer.com Personal Trainer Michael Behnken, MS, NASM-CPT-PES, CSCS The standard BOSU crunch is a great progression from crunches on the floor. This is due to the increased range of motion because of the round surface of the ball. To increase the difficulty place your lower back towards the top of the BOSU which will form a long lever crunch. The Lowest level of this abdominals exercise would be with your butt touching the floor and hands across the chest. Always keep your core drawn in during your abdominal crunches to increase their effectiveness. As with all core and abs exercises, stop if you experience lower back pain. San Francico Personal Training http://fitSF.com