Hollow body position
The hollow body position (alongside with the arch position) defines midline stability for gymnasts and is the basis for solid gymnastics movement. It is probably the most important exercise not just in CrossFit gymnastics but in CrossFit in general.
To perform the hollow body position press your low back onto the ground making sure there’s no space between it and the floor. Then, lift your legs up with your toes pointed and bring the arms up overhead, all along making to keep your lower back stuck to the floor beneath.
The arch body position is achieved through a strong contraction of the posterior kinetic chain while lying prone on the ground. The arch is less technical than the hollow, yet also activates tissue throughout the body.
These two positions are seen not only in static movements but in dynamic ones as well. Their aim is to create as much tension as possible, as this will translate into power.
A really good understanding of the foundation of the hollow and arch body positions is very important.