Exercise Ball Frog Crunch
- Target muscle
- Rectus Abdominis
- Synergist muscles
- Adductor Brevis, Adductor Longus, Obliques, Pectineous, Quadriceps, Sartorius, Tensor Fasciae Latae
- Equipment
- Stability ball
- Body part
- Waist
- Type
- Strength
The exercise ball frog crunch is a core strength move that primarily targets the rectus abdominis (the front "six-pack" muscle). With the soles of the feet pressed together and knees splayed out in a frog position, the obliques, hip adductors (adductor longus, adductor brevis, pectineus), quadriceps, sartorius, and tensor fasciae latae all assist as you curl your trunk. Done on a stability ball, it adds an extra balance demand that keeps the core working throughout.
How to do the Exercise Ball Frog Crunch
- 1Sit on the stability ball, then walk your feet forward and lean back until the ball supports your lower and mid back.
- 2Press the soles of your feet together and let your knees drop open to the sides into a frog position.
- 3Place your hands lightly behind your head or crossed over your chest, and let your trunk extend back over the ball to lengthen the abs.
- 4Brace your core and exhale as you curl your head, shoulders, and upper back up off the ball.
- 5Crunch until you feel a strong contraction in your abdominals, keeping your knees open and feet together throughout.
- 6Pause briefly at the top without pulling on your neck.
- 7Inhale and lower under control back over the ball to the starting stretch.
- 8Complete your reps, then walk your feet back and sit up off the ball with control.
Form tips
- Keep the movement slow and controlled in both directions so your abs do the work instead of momentum.
- Let your fingers rest lightly behind your head and lead with your chest — never yank on your neck to pull yourself up.
- Keep the soles of your feet pressed together and knees splayed the whole set to maintain the frog position and hip engagement.
- Exhale and pull your ribs toward your hips at the top of each rep to maximize the contraction in the rectus abdominis.
- Position the ball under your lower-to-mid back so you can extend slightly over it at the bottom for a full range of motion.
Common mistakes
- Pulling on your head with your hands, which strains the neck and takes tension off the abs.
- Using momentum to swing up instead of curling slowly, which reduces the load on the rectus abdominis and risks rolling off the ball.
- Letting the knees drift back together, which removes the frog position and the hip-adductor involvement.
- Crunching with a short, choppy range of motion instead of extending over the ball first, which limits how much the abs are worked.
- Holding your breath through the rep, which makes it harder to brace the core and complete the contraction.
Frequently asked questions
What muscles does the exercise ball frog crunch work?
It primarily works the rectus abdominis, with the obliques, hip adductors (adductor longus, adductor brevis, pectineus), quadriceps, sartorius, and tensor fasciae latae assisting as you curl your trunk in the frog position.
Why are the feet together and knees out in this crunch?
The frog position — soles together, knees splayed — engages the hip adductors and flexors alongside the abs, and it keeps your legs from helping you cheat the rep, so the rectus abdominis does more of the work.
Is the exercise ball frog crunch good for beginners?
Yes. It uses only a stability ball and your bodyweight, but the ball adds a balance challenge, so beginners should start with a short range of motion and focus on control before adding reps.
How many sets and reps should I do?
For most lifters, 2–4 sets of 12–20 controlled reps works well. Since this is a bodyweight core move, aim for clean form and a full contraction rather than chasing high numbers.
Where should I feel this exercise?
You should feel it mainly in the front of your abs (the rectus abdominis), with some work along the obliques and the inner-thigh and hip-flexor muscles that hold the frog position. If you feel it in your neck, you are pulling with your hands instead of curling with your core.
