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  3. Exercises
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  5. Shoulders
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  7. Seated Knee Slap On Chair

Exercise guide

Seated Knee Slap On Chair

  • Beginner
  • Compound
  • Rep-based
  • Lower legs
  • Shoulders
  • Upper arms
  • Waist

This beginner-friendly core exercise improves hip flexor strength and abdominal stability while incorporating a rotational element to engage the obliques. It builds functional coordination and core endurance from a stable, seated position, making it ideal for those with limited mobility or as a dynamic warm-up.

Reviewed by the Crucible Fit team · Updated June 2026

Watch the Seated Knee Slap On Chair demonstrationVideo and instructions for every movement are in the Crucible Fit app.

Muscles worked

Primary

  • Abs
  • Obliques
  • Pectorals

Secondary

  • Deltoids
  • Lats
  • Serratus anterior

Equipment

  • Body weight

Setup

  1. Sit upright on the edge of a sturdy chair or step with your feet flat on the floor, hip-width apart.
  2. Engage your core and maintain a tall, neutral spine with your shoulders pulled back and down.
  3. Place your hands resting lightly on your thighs to begin.

How to do it

  1. Exhale as you lift your right knee toward your chest while simultaneously rotating your torso to slap the top of the knee with your left hand.
  2. Inhale as you lower your leg and return your torso to the center with control.
  3. Repeat the movement on the opposite side, lifting your left knee and slapping it with your right hand.
  4. Maintain a steady, rhythmic tempo, ensuring you do not use momentum to swing your limbs.

Form checklist

  • Keep your chest lifted and avoid rounding your lower back as you lift the knee.
  • Focus on rotating from the waist rather than just reaching across with the arm.
  • Ensure your stationary foot remains firmly planted on the floor for stability.
  • Control the descent of the leg to keep constant tension on the hip flexors and abdominals.

Pro tips

  • To maximize pectoral and oblique engagement, press your hand firmly into your knee at the top of the movement for a one-second isometric hold.
  • Focus on the 'crunch' sensation by imagining you are bringing your bottom rib toward your opposite hip bone.

Make it harder

  • Perform the movement without letting your feet touch the ground between repetitions to keep the core under constant tension.
  • Hold a light dumbbell or medicine ball in both hands and rotate the weight toward the rising knee to increase the load on the obliques and shoulders.

Frequently asked

What muscles does the seated knee slap on chair work?
The seated knee slap on chair primarily targets the abs, obliques, and pectorals, and also works the deltoids, lats, and serratus anterior as secondary muscles.
What equipment do you need for the seated knee slap on chair?
The seated knee slap on chair requires no equipment — just your body weight.
Is the seated knee slap on chair good for beginners?
Yes. The seated knee slap on chair is a beginner-friendly movement and a strong foundation to build on.

Related exercises

  • 45 Degrees Arms PlankIntermediate · abs, deltoids, obliques, and pectorals
  • Battling Ropes Half KneelingIntermediate · abs, biceps, deltoids, obliques, and pectorals
  • Behind The Head Ball SlamIntermediate · abs, calves, lats, obliques, and pectorals
  • Bosu Ball Plank HoldIntermediate · 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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