Flip your regular plank 180 degrees to challenge your balance and hit your core, glutes and hips in a whole new way.
Sit on the floor with your hands on either side of your hips, fingers forward, legs straight. Lift your hips so your body makes a straight line from your head to your heels. Your head and neck should be neutral, and your arms should be straight.
Lift one leg as high as you can into the air, keeping it straight, and hold for three slow breaths. Lower, then repeat on the other leg. Do three sets of 10 reps (five each side).