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  1. Home
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  3. Exercises
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  5. Core & Abs
  6. /
  7. Open And Knee Tuck On A Padded Stool

Exercise guide

Open And Knee Tuck On A Padded Stool

  • Beginner
  • Compound
  • Rep-based
  • Waist

This core-focused movement targets the entire abdominal wall and hip flexors by combining a seated crunch with leg extension. It improves trunk stability and lower-body control using the stool as a pivot point for a full range of motion.

Reviewed by the Crucible Fit team · Updated June 2026

Watch the Open And Knee Tuck On A Padded Stool demonstrationVideo and instructions for every movement are in the Crucible Fit app.

Muscles worked

Primary

  • Abs
  • Obliques

Secondary

  • Hip flexors

Equipment

  • Body weight

Setup

  1. Sit on the edge of the padded stool with your hands gripping the sides just behind your hips for support.
  2. Lean your torso back slightly to a 45-degree angle while lifting your feet off the floor.
  3. Bring your knees toward your chest to find your balance in the starting tuck position.

How to do it

  1. Inhale and slowly extend your legs straight out in front of you while leaning your torso back further to open the body into a V-shape.
  2. Exhale and pull your knees back toward your chest, simultaneously crunching your upper body forward to meet them.
  3. Maintain a controlled tempo, spending 2 seconds on the extension and 1 second on the contraction.

Form checklist

  • Keep your core braced and avoid letting your lower back arch excessively during the extension.
  • Ensure your feet do not touch the ground at any point during the set.
  • Keep your shoulders down and away from your ears to avoid neck tension.
  • Move your torso and legs simultaneously to maintain a fluid opening and closing motion.

Pro tips

  • At the peak of the tuck, focus on pulling your belly button toward your spine for a deeper abdominal contraction.
  • Squeeze your inner thighs and quadriceps together during the extension to increase stability and lower-ab engagement.

Make it harder

  • Remove your hands from the stool and reach them forward or out to the sides to remove the balance assist.
  • Slow down the extension phase to 4 seconds to significantly increase time under tension.

Frequently asked

What muscles does the open and knee tuck on a padded stool work?
The open and knee tuck on a padded stool primarily targets the abs and obliques, and also works the hip flexors as secondary muscles.
What equipment do you need for the open and knee tuck on a padded stool?
The open and knee tuck on a padded stool requires no equipment — just your body weight.
Is the open and knee tuck on a padded stool good for beginners?
Yes. The open and knee tuck on a padded stool 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

Train it with Crucible Fit.

Every movement in this library is in the app with video and instructions, ready for your own sessions on the days between Crucibles. Your first Crucible is on us.

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