Your pelvis, diaphragm, and jaw share something special: they all have (or are) structures that are parallel to the ground when you're upright and have a different relationship with gravity compared to say your quads. They developed around the same time in utero and have similar anatomical shapes. They also have similar reactions to stress when you're startled or angry. Because they have different characteristics from your other muscles, we address them in unusual ways. Notice the difference when you relax your deep core.
Coregeous Ball, the straw that came with your Coregeous Ball (or drinking straw), Alpha Ball, Original Size Yoga Tune Up Balls, Block