Low Plank Oblique Knee
Start in a low plank on elbows. Bring one knee up to your elbow on the same side. Return the toe to plank. Then bring the opposite knee up and back. Continue to alternate. Keep your booty down. Keep core and abs engaged. Squeeze glutes and inner thighs together as you return to plank position.
Modify by doing it all from your knees.
Core. Abs. Shoulders. Chest. Glutes.