Frog Sit-up
- Synergist muscles
- Adductor Magnus, Gracilis, Obliques
- Equipment
- Body weight
- Body part
- Waist
- Type
- Strength
The frog sit-up is a bodyweight core exercise performed with the soles of your feet pressed together and knees splayed wide (the "frog" position). By externally rotating the hips, it shifts work from the legs onto the deep hip flexors (iliopsoas, pectineus) and inner-thigh adductors (adductor brevis, adductor longus) while the rectus abdominis drives the trunk up. It's a useful variation for building abdominal and hip-flexor strength without any equipment.
How to do the Frog Sit-up
- 1Lie flat on your back and press the soles of your feet together, letting your knees fall open to the sides so your legs form a diamond (frog position).
- 2Draw your heels in toward your groin until you feel a gentle stretch through your inner thighs and hips.
- 3Extend your arms overhead or place your hands lightly behind your head without pulling on your neck.
- 4Brace your core and exhale as you curl your head, shoulders, and upper back off the floor.
- 5Continue lifting toward your feet, keeping your knees splayed and your feet pressed together throughout.
- 6Pause briefly at the top, squeezing your abs and feeling the contraction through your hip flexors.
- 7Inhale and lower your torso back down with control until your shoulder blades touch the floor.
- 8Repeat for your target reps, keeping the frog position consistent on every rep.
Form tips
- Keep the soles of your feet pressed together for the whole set — letting them drift apart reduces the inner-thigh and hip-flexor involvement.
- Initiate each rep by curling your ribcage toward your pelvis rather than yanking with your arms.
- Exhale hard at the top to deepen the abdominal contraction, and inhale on the way down.
- Move at a steady tempo and control the lowering phase instead of dropping back to the floor.
- If you feel strain in your lower back, slide your heels slightly farther from your body to reduce the lever and stay grounded.
Common mistakes
- Pulling on the back of your head with your hands, which strains the neck and shifts effort away from the abs.
- Letting the knees collapse inward or the feet separate, which removes the adductor and hip-rotation challenge that defines the movement.
- Using momentum to swing up instead of curling under control, which reduces tension on the abs and hip flexors.
- Holding your breath through the rep, which spikes pressure and weakens your core brace.
- Lifting only the head and neck instead of curling the upper back off the floor, cutting the range of motion short.
Frequently asked questions
What muscles does the frog sit-up work?
It primarily targets the rectus abdominis, the hip flexors (iliopsoas, pectineus), and the inner-thigh adductors (adductor brevis and longus). The adductor magnus, gracilis, and obliques assist as synergists.
How is the frog sit-up different from a regular sit-up?
In a frog sit-up your feet are pressed together with the knees splayed out (hips externally rotated) instead of feet flat on the floor. This position recruits the hip adductors and deep hip flexors more than a standard sit-up does.
Is the frog sit-up good for beginners?
Yes. It uses only body weight and is self-limiting, so you can start with a small range of motion and arms across your chest, then progress to arms overhead as your core gets stronger.
How many sets and reps should I do?
Aim for 2–4 sets of 12–20 controlled reps. Since it's a bodyweight movement, focus on full range and a strong squeeze at the top rather than rushing through high numbers.
Where should I feel the frog sit-up?
You should feel it mainly in your abs, with noticeable work through the front of your hips and inner thighs. If you only feel it in your neck or lower back, slow down and curl from the ribcage.
