This exercise strengthens the muscles used when you inhale. In the workout videos, our model is doing Diaphragm Extensions with no weight. In this technique video, he is using a stack of books for resistance. If you want more of a challenge or this is not your first time through the course, consider adding some weight. Place some books, a plate weight, a kettlebell, etc. on your belly when doing this exercise. When using a weight, hold it with one hand and move it to different parts of the belly always focusing on pushing the weight away on the inhale.