Frog Sit-Ups
Frog Sit-Ups have you lie on your back with the soles of your feet pressed together and your knees dropped out to the sides, then curl your torso up toward your feet. The wide, open leg position takes your hip flexors out of the movement more than a standard sit-up does, shifting more of the work onto your abdominals. It's a straightforward bodyweight option for anyone building ab strength without any equipment.
Why it works
A standard sit-up lets the hip flexors, the muscles that run from your thighs to your spine, share a lot of the workload, especially once your feet are anchored. Pressing your feet together and dropping your knees out to the sides changes your hip position enough that the hip flexors have a harder time contributing, which leaves the abdominals doing more of the work of curling your torso up. That makes Frog Sit-Ups a useful variation when you want to feel a sit-up more directly in your abs rather than your hip flexors.
Set up
- Lie on your back with the soles of your feet pressed together and your knees dropped open to the sides.
- Let your feet rest a comfortable distance from your hips, wherever your hip flexibility allows.
- Place your hands lightly behind your head or crossed over your chest.
- Relax your neck and keep your chin slightly tucked before you start.
How to do it
- Exhale and curl your torso up off the floor, leading with your chest rather than your chin.
- Continue curling until you're sitting most of the way upright, or as far as you can with control.
- Pause briefly at the top and squeeze your abs.
- Lower back down slowly, keeping your feet pressed together the whole time.
- Let your shoulder blades touch the floor before starting the next rep.
- Keep the pace steady rather than using momentum to snap up.
Form cues
- Feet stay pressed together, knees stay open, the whole set.
- Lead the curl with your chest, not your chin or elbows.
- Exhale on the way up, that helps the abs contract fully.
- Control the descent, don't just drop back down.
Breathing: Exhale as you curl up toward your feet, inhale as you lower back down.
Common mistakes
Pulling on the neck with the hands to help curl up.
Fix: Keep your hands lightly behind your head for support only, and initiate the curl from your abs instead of tugging your neck forward.
Letting the feet drift apart during the set.
Fix: Keep the soles of your feet pressed together throughout; that position is what shifts the work toward the abs.
Using momentum to snap up instead of a controlled curl.
Fix: Slow the rep down and focus on curling your spine up one segment at a time.
Stopping the movement only at the very bottom or top without control in between.
Fix: Keep tension on the abs through the full range, both curling up and lowering back down.
How to program it
- Three sets of 12 to 15 reps is a solid target once the hip position feels comfortable and controlled.
- This is bodyweight ab isolation work, so 3 to 4 times a week is reasonable if you're not sore or fatigued from other ab training.
- It fits well near the end of a session, since fresh hip flexors aren't needed for this variation to work.
- Progress by slowing the tempo or adding a brief pause at the top before increasing reps further.
Safety notes
- Skip this variation if the open-knee position causes hip or groin discomfort, and use a standard sit-up instead.
- Keep your neck relaxed throughout; if you feel strain in your neck rather than your abs, lighten the pull of your hands and slow down.
Exercise profile
- Force
- Pull
- Mechanics
- Isolation
- Category
- Strength
Frequently asked questions
How many Frog Sit-Ups should I do per set?
12 to 15 controlled reps per set is a good target for most people. Focus on a full, controlled curl rather than rushing to a higher number.
Frog Sit-Ups vs regular sit-ups, what's the difference?
Pressing your feet together and dropping your knees out to the sides changes your hip position enough to reduce how much your hip flexors can help, which shifts more of the work onto your abdominals compared to a standard sit-up.
Can I do Frog Sit-Ups if my hips are tight?
If the open-knee position feels uncomfortable in your hips or groin, it's fine to widen your knees less or switch to a standard sit-up instead. There's no need to force a position that doesn't feel right.
Why do I feel Frog Sit-Ups in my neck instead of my abs?
That usually means the hands are pulling the head forward to help curl up. Rest your hands lightly behind your head instead of interlocking and pulling, and let your abs initiate the movement.