The flip side of the hollow body position is the arch hold -aka Superman. Both positions are equally important. To perform the arch hold, start by laying flat on your stomach with your arms covering your ears and your feet glued together. Simultaneously lift your head, chest and shoulders as you lift your heels up and squeeze your glutes.
Work both the arch and hollow body positions for your strength conditioning. I suggest you stretch between sets. The best opposition stretches are cobra for the hollow body hold and cat for the arch hold.
As you get stronger, progress to the rocking for both the hollow body and the arch holds. Now, get strong!