Knee In And Out Crunch

Muscles worked

Setup

1. Sit on the floor with your knees bent and feet flat on the ground.
2. Place your hands on the floor slightly behind your hips with fingers pointing toward your feet for support.
3. Lean your torso back at a 45-degree angle and lift your feet a few inches off the floor, finding your balance on your sit bones.

How to do it

1. Exhale and pull your knees toward your chest while simultaneously bringing your torso forward to meet them.
2. Inhale and extend your legs straight out in front of you while leaning your torso back, keeping your feet hovering just above the floor.
3. Move in a fluid, rhythmic motion, ensuring your core remains braced throughout the entire range.
4. Maintain a controlled tempo, taking approximately 2 seconds for the extension and 1 second for the crunch.

Form checklist

• Keep your chest lifted and avoid rounding your shoulders forward.
• Ensure your lower back does not arch excessively when extending your legs.
• Keep your feet and knees squeezed together throughout the movement.
• Use your hands only for balance rather than pushing off the floor to create momentum.

Pro tips

• To maximize muscle fiber recruitment, focus on pulling your belly button toward your spine during the crunch phase.
• Pause for a split second at the point of full extension to challenge your deep core stabilizers.

Make it harder

• Perform the exercise with your hands lifted off the floor and reached out to your sides to remove the base of support.
• Slow down the extension phase to a 4-second count to increase time under tension.

Frequently asked

What muscles does the knee in and out crunch work?

The knee in and out crunch primarily targets the abs and obliques, and also works the erector spinae as secondary muscles.

What equipment do you need for the knee in and out crunch?

The knee in and out crunch requires no equipment — just your body weight.

Is the knee in and out crunch good for beginners?

Yes. The knee in and out crunch is a beginner-friendly movement and a strong foundation to build on.

Related exercises

• 3/4 Sit-UpBeginner · abs and obliques
• 45 Degree Bicycle Twisting CrunchIntermediate · abs and obliques
• 45 Degree Lean Back Alternate Knee RaiseBeginner · abs and obliques
• 45 Degrees Arms PlankIntermediate · abs, deltoids, obliques, and pectorals