Stability Ball Jackknife Sit-Up
A core stability exercise performed from a high plank position with shins on a stability ball, tucking the knees toward the chest to target the abdominals and hip flexors.
About Exercise
Equipment
Stability Ball
Difficulty
4/5 • Intermediate
Primary Muscle Groups
Hip Flexors, Abs, Obliques
Secondary Muscles
Glutes, Hamstrings, Quads
Accessory Muscles
Shoulders
Popularity Score
7
Goals
Training Style
Setup Requirements
Requires Rack
No
Requires Bench
No
Requires Spotter
No
Space Needed
Small
Noise Level
Low
Muscle Breakdown
View Muscle MapAbs
10/10Rectus Abdominis
Hip Flexors
9/10Iliopsoas
Obliques
8/10External Obliques, Internal Obliques
Glutes
4/10Glute Max
Hamstrings
3/10Biceps Femoris
Quads
3/10Rectus Femoris
Shoulders
2/10Anterior Delts
Programming
Typical Rep Range
8-20 reps
Rest Between Sets
30-60 seconds
How to Perform
Start in a high plank position with hands placed shoulder-width apart on the floor and shins resting on top of a stability ball.
- Brace your core to maintain a straight line from head to heels.
- Exhale and tuck your knees toward your chest, rolling the ball forward.
- Squeeze your abdominals hard as the knees approach the chest.
- Pause briefly at the top of the movement.
- Inhale and slowly extend your legs back to the starting plank position.
- Maintain a neutral spine and avoid sagging the hips.
Coaching Tips
Form Cues
- Hands under shoulders
- Ribs down
- Don't sag hips
- Control the roll
- Eyes on floor
Breathing
Exhale as you tuck your knees in; inhale as you extend your legs back out.
Tempo
2-1-2
Range of Motion
From full leg extension in a plank to knees tucked near the chest.
Safety
Safety Notes
- Ensure the ball is properly inflated.
- Stop if you feel sharp lower back pain.
- Maintain wrist alignment.
Spotting
Not recommended; ensure clear space around the ball.
Common Mistakes
- Sagging hips
- Piking hips too high
- Rushing the tempo
- Shoulders drifting back
- Bending elbows
When to Avoid
- Acute lower back injury
- Shoulder impingement
- Wrist instability
- Recent abdominal surgery
Flexibility Needed
- Adequate shoulder flexion for plank
- Core stability to hold neutral spine
- Hip mobility for flexion
Build Up First
- Proficient high plank hold
- Basic hip flexion control
- Familiarity with stability ball balance
Also known as
Swiss Ball Jackknife, Physio Ball Jackknife, Stability Ball Knee Tuck, Ball Knee Tuck
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