Crunch (legs on stability ball)
- Target muscle
- Rectus Abdominis
- Synergist muscles
- Obliques
- Equipment
- Stability ball
- Body part
- Waist
- Type
- Strength
The crunch with legs on a stability ball is a floor abdominal exercise that targets the rectus abdominis, with the obliques assisting to keep the trunk stable. You lie on your back with your lower legs resting on the ball, which fixes your hips and lets you focus on flexing the spine through a controlled, short range.
How to do the Crunch (legs on stability ball)
- 1Lie on your back on the floor and rest your lower legs and calves on top of the stability ball, with your hips and knees bent at roughly 90 degrees.
- 2Settle the ball so it sits comfortably under your calves, keeping your thighs roughly vertical and your shins level.
- 3Place your hands lightly behind your head or crossed over your chest, and pull your ribs down to flatten your lower back into the floor.
- 4Exhale and curl your head, shoulders, and upper back off the floor by contracting your abs, lifting until your shoulder blades clear the ground.
- 5Pause briefly at the top and squeeze your abdominals, keeping your neck relaxed and your chin off your chest.
- 6Inhale and lower your upper back to the floor under control, keeping tension on the abs rather than dropping.
- 7Complete your reps, then lower your head fully and slide your legs off the ball to finish.
Form tips
- Lead the movement with your ribs and breastbone, not your head, so the abs do the work and your neck stays relaxed.
- Keep the stability ball still under your calves throughout the set; if it rolls, you are using your legs instead of your abs.
- Move only through a short range until your shoulder blades clear the floor, rather than trying to sit all the way up.
- Exhale hard as you crunch up to drive a stronger abdominal contraction.
Common mistakes
- Pulling on your head with your hands, which strains the neck and takes tension off the abs.
- Pushing into the ball with your legs to swing yourself up, which turns the rep into a leg movement and cheats the abs.
- Yanking up with momentum instead of curling slowly, which removes tension and reduces the work on the rectus abdominis.
- Letting your lower back arch off the floor, which loses core bracing and can stress the spine.
Frequently asked questions
What muscles does the crunch with legs on a stability ball work?
It primarily works the rectus abdominis (the front abdominal wall), with the obliques assisting to stabilize the trunk as you curl up.
Why rest my legs on a stability ball for crunches?
Resting your lower legs on the ball fixes your hips at about 90 degrees, which limits hip-flexor involvement and helps you isolate the abdominals through a controlled crunch.
Is this crunch good for beginners?
Yes. It uses only body weight and a short range, so it is a beginner-friendly way to build abdominal strength. Cross your arms over your chest to make it easier, or place your hands behind your head to make it slightly harder.
How many sets and reps should I do?
Two to three sets of 12 to 20 controlled reps is a sensible default. Focus on a strong squeeze each rep rather than chasing high numbers with momentum.
Where should I feel this exercise?
You should feel it in the front of your abdominals as you curl up. If you feel it mainly in your neck or hip flexors, slow down, relax your neck, and stop driving with your legs into the ball.
