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  3. Exercises
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  5. Core & Abs
  6. /
  7. Lying Tuck-Up

Exercise guide

Lying Tuck-Up

  • Beginner
  • Compound
  • Rep-based
  • Waist

The Lying Tuck-Up is a dynamic bodyweight exercise that targets the entire abdominal wall and hip flexors by synchronizing upper and lower body flexion. It is highly effective for building foundational core strength and improving coordination between the torso and lower extremities.

Reviewed by the Crucible Fit team · Updated June 2026

Watch the Lying Tuck-Up demonstrationVideo and instructions for every movement are in the Crucible Fit app.

Muscles worked

Primary

  • Abs
  • Obliques

Secondary

  • Erector spinae
  • Hip flexors

Equipment

  • Body weight

Setup

  1. Lie flat on your back on a mat with your legs fully extended and feet together.
  2. Place your arms by your sides with palms facing down for stability, or hover them slightly off the floor.
  3. Engage your core by pressing your lower back firmly into the mat to eliminate any arching.

How to do it

  1. Exhale as you simultaneously lift your torso off the floor and pull your knees toward your chest.
  2. Balance on your glutes at the peak of the movement, bringing your chest and knees as close together as possible.
  3. Inhale as you slowly lower your torso and legs back toward the floor in a controlled manner.
  4. Stop just before your head or heels touch the ground to maintain constant tension on the abs.

Form checklist

  • Maintain a synchronized movement where the upper body and knees meet at the same time.
  • Keep your chin tucked slightly toward your chest to avoid neck strain.
  • Ensure your lower back makes contact with the floor first during the descent.
  • Avoid using momentum or swinging your arms to pull yourself up.

Pro tips

  • Focus on the 'crunch' sensation by trying to minimize the distance between your ribcage and hip bones.
  • Pause for a one-second hold at the top of the movement to maximize peak contraction of the rectus abdominis.

Make it harder

  • Keep your arms extended overhead throughout the entire movement to increase the lever length and difficulty.
  • Slow down the eccentric (lowering) phase to a 3-second count to increase time under tension.

Frequently asked

What muscles does the lying tuck-up work?
The lying tuck-up primarily targets the abs and obliques, and also works the erector spinae and hip flexors as secondary muscles.
What equipment do you need for the lying tuck-up?
The lying tuck-up requires no equipment — just your body weight.
Is the lying tuck-up good for beginners?
Yes. The lying tuck-up 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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