Resisted bilateral knee fall out ("Knee fall out, resisted" Core/abdominal stabilization, supine, drop out)

Lie on your back with your knees bent and your feet flat on the floor.
Tie a resistance band around your knees.
Tighten your core stability muscles before slowly dropping both knees out to the side, against the resistance of the band.
Keep your core muscles working whilst you bring your knees back up to the starting position.
Do not allow your body or pelvis to rotate during this movement, and keep your lower back flattened.