To perform
Hollow Body Extensions, lay on your back and lift your hands and feet upwards towards each other with your lower back pressed strongly into the ground.
Similar to
the Hollow Body Extension, you will lower your feet and hands, this time with kettlebells, away from each other.
Then, pressing the lower back strongly into the ground, lift and lower your legs as you did with
the Hollow Body Extension and hold.
A Hollow Body Hold is simply holding the bottom position of
the Hollow Body Extension.