The dumbbell sit-up is a great exercise for training abs. If you desire a flat-belly, you'll want to include this exercise in your routine. If regular floor sit-ups are too easy, use a dumbbell to increase the resistance on the abs. The hip flexors are also involved in the sit-up. The goal is to continually challenge the abs to grow stronger. Keep the rest periods to a minimum and your get more results in less time.
Dumbbell Sit Up