Mike is one of the best trainers around for functional training.
The video above is an exercise that challenges the core in rotation. This engages rotational core muscles such as abdominal obliques as well as deep muscles that rotate the spine. It does not load the spine like seated or standing rotational exercises.
Be sure to keep the thighs vertical and your knees and ankles together with this exercise. Not all patients can do this, but to those who can, it is a missing link in core training. ENJOY.