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Last updated March 2, 2026
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abs
Jack Knife (Suspension)
Place your feet in suspension straps and pull your knees toward your chest from a plank position.
Quick facts
- Difficulty
- Moderate
- Mechanic
- Compound
- Force
- Pull
- Type
- Strength
- Injury Risk
- Low
- Hypertrophy
- Medium
- Calorie Burn
- Medium
Muscle focus
Primary and secondary muscle groups targeted by this movement.
Primary
abship flexors
Secondary
deep abs / coreside abs / obliquesfront shoulders
Equipment & setup
What you need and how to position yourself before starting.
Equipment
suspension
Movement pattern
Bilateral
Posture
Lying
Tracking parameters
reps
Step-by-step instructions
Follow these cues to master proper technique and stay safe through every rep.
- Step 1Setup
- Attach suspension straps at an appropriate height.
- Place your feet in the foot cradles and assume a push-up position.
- Hands should be directly under your shoulders.
- Step 2Starting Position
- Your body should form a straight line from head to heels.
- Engage your core and glutes to maintain stability.
- Keep your arms locked out.
- Step 3Execution
- Tuck your knees toward your chest by flexing your hips and spine.
- Keep your upper body as stable as possible.
- Squeeze your abs hard at the peak contraction.
- Slowly extend your legs back to the plank position under control.
- Avoid letting your hips sag between reps.