Raised Bridges with Leg Lift
Start with both hands on the floor, arms vertical, and supporting your body in an oblique posture. Contract the abdominals to raise your hips.
Proceed to slowly raise one leg to 45 degrees or better. Contract the abs and butt for 1-2 seconds, just enough to lift your hips a couple of inches further; relax without changing your stance. Repeat 5-10 times each side.