The spinal balance works your core stabilization and your glutes. 

Spinal balance form cue:

Come onto hands and knees (hands under your shoulders and knees under your hip bones). Extend one arm and the opposite leg, keeping your hips parallel to the floor. Flex your foot and gently pulse your heel up towards the ceiling (or sky!). Squeeze your glute to lift your leg and keep your core engaged.

Head back to the form cue library here.