How to do it:
- Start on your hands and knees, with your shoulders directly over your hands and your hips over your knees (shown).
- Tighten your abdominals and keep them engaged throughout the set.
- Lift your left leg into the air until the sole of your shoe is facing the ceiling and your thigh is parallel to the floor.
- Slowly lower the knee until it’s hovering just above the floor, then lift and lower eight times.
- Switch legs.
Bonus benefits: This move also tightens the abdominals and strengthens the muscles in the lower back.
Make it harder: Try it with your back leg extended straight out behind you. When you can do this move easily, add an abs challenge: Raise your right arm and hold it parallel to the floor as you lift and lower your left leg. After one set, switch arms and legs. You’ll need to engage your core to keep your body stable.