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  7. Single Leg Stretch Bent Knee

Exercise guide

Single Leg Stretch Bent Knee

  • Beginner
  • Compound
  • Timed hold
  • Waist

This Pilates-based core exercise builds abdominal endurance and pelvic stability by challenging the midsection to remain still while the limbs move. It effectively targets the deep core and hip flexors while promoting coordination and spinal flexion.

Reviewed by the Crucible team · Updated June 2026

Watch the Single Leg Stretch Bent Knee demonstrationGuided video and your full workout live in the Crucible app.

Muscles worked

Primary

  • Abs
  • Obliques

Secondary

  • Erector spinae
  • Serratus anterior

Equipment

  • Body weight

Setup

  1. Lie flat on your back with your knees bent and feet flat on the floor.
  2. Lift both legs into a tabletop position with knees stacked over hips and shins parallel to the floor.
  3. Curl your head, neck, and shoulders off the mat, looking toward your thighs to engage the upper abs.
  4. Place both hands on your right shin, with the outside hand near the ankle and the inside hand near the knee.

How to do it

  1. Exhale as you extend your left leg straight out to a 45-degree angle while pulling the right knee toward your chest.
  2. Inhale as you begin to switch legs, bringing the left knee in and extending the right leg out.
  3. Exhale again as you complete the switch, pulling the left knee toward your chest and reaching the right leg long.
  4. Maintain a controlled, rhythmic tempo, ensuring your torso remains stationary as the legs cycle.

Form checklist

  • Keep your lower back pressed firmly into the mat; do not let it arch as the leg extends.
  • Maintain the lift of your shoulder blades off the floor throughout the entire set.
  • Keep your elbows wide and chest open to avoid straining the neck.
  • Ensure the extending leg is fully straight with toes pointed to engage the quadriceps and glutes.

Pro tips

  • Focus on the 'opposition' by reaching the long leg away from your center while pulling the bent knee in to maximize abdominal tension.
  • Engage your glutes as you reach the leg long to stabilize the pelvis and deepen the lower abdominal work.

Make it harder

  • Lower the extending leg closer to the floor (2-3 inches above the mat) to increase the lever length and core demand.
  • Perform the movement with your hands behind your head to remove the assistance of the arm pull and increase the load on the obliques.

Frequently asked

What muscles does the single leg stretch bent knee work?
The single leg stretch bent knee primarily targets the abs and obliques, and also works the erector spinae and serratus anterior as secondary muscles.
What equipment do you need for the single leg stretch bent knee?
The single leg stretch bent knee requires no equipment — just your body weight.
Is the single leg stretch bent knee good for beginners?
Yes. The single leg stretch bent knee 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 this with a plan, not guesswork

Crucible builds the single leg stretch bent knee into a precise program around your body, equipment, location, and time.

Download on the App Store