Reverse Crunch: Form, Mistakes and Progressions
The reverse crunch is the simplest way to train the lower part of your abs. Here is how to do it right and how to make it harder over time.
A reverse crunch is a floor exercise where you curl your hips off the ground toward your ribcage, instead of lifting your shoulders toward your hips like a normal crunch. Done well, it's one of the best bodyweight moves for the lower part of the rectus abdominis. The secret is that the movement is small: you're rolling your pelvis, not swinging your legs.
Below is a step-by-step guide, the most common mistakes, and a progression path so the exercise keeps challenging you.
What the reverse crunch works
The main target is the rectus abdominis, with extra emphasis on its lower fibers because the pelvis is the moving part. Your obliques and deep core help stabilize, and your hip flexors hold your knees in position.
The movement trains posterior pelvic tilt, meaning the ability to tuck your tailbone under and flatten your lower back. That skill matters beyond looks. It's the same control you need for hollow holds, hanging leg raises and keeping a neutral spine in lifts like the squat.
For a full lower-ab session built around this move, see our lower ab workout.
How to do a reverse crunch
- Lie on your back with arms by your sides, palms down. You can also hold a bench or post behind your head for stability.
- Lift your legs so your hips and knees are bent to about 90 degrees, shins parallel to the floor.
- Exhale and brace your stomach as if someone is about to poke it.
- Use your abs to curl your pelvis up and back so your hips lift a few inches off the floor and your knees move toward your chest.
- Pause for a second at the top. Your lower back should be rounded off the floor.
- Lower slowly, vertebra by vertebra, until your tailbone touches down. Keep your knees bent the whole time.
- Inhale at the bottom and repeat.
Aim for 2 seconds up, a 1-second pause, and 3 seconds down. That slow lowering is where a lot of the training effect comes from.
Common mistakes
Swinging the legs
If your knees fly back and forth, momentum is doing the work. The fix is to stop at the bottom, kill any swing, and start each rep from a dead stop.
Moving at the hips instead of the spine
Bringing your knees to your chest without lifting your hips is just hip flexion. The hips need to curl off the floor. Think "roll the tailbone up," not "bring the knees in."
Pushing hard with the hands
A little pressure from your palms is fine. If you're shoving the floor to get up, the exercise is too hard. Try a smaller range or a regression.
Dropping the legs too far
Letting your feet drop toward the floor between reps lengthens the lever and can arch your back. Keep the knees bent at roughly 90 degrees.
Rushing
Fast reps feel productive but often skip the hardest part. If you can do 30 quick reps but struggle with 10 slow ones, the slow ones are your real working sets.
Reverse crunch progressions
Work through these in order. Move on when you can do 3 sets of 15 clean reps at the current level.
| Level | Variation | Why it's harder |
|---|---|---|
| 1 | Pelvic tilt on the floor (feet down) | Learns the tuck with minimal load |
| 2 | Reverse crunch, feet tapping floor | Short lever, partial range |
| 3 | Standard reverse crunch | Full curl with bent knees |
| 4 | Slow-eccentric reverse crunch (5 seconds down) | More time under tension |
| 5 | Decline bench reverse crunch | Gravity resists through a bigger range |
| 6 | Reverse crunch with straighter legs | Longer lever |
| 7 | Hanging knee raise with pelvic curl | Full bodyweight, then onto hanging leg raises |
You can also hold a light dumbbell between your feet or knees at levels 3-5. Start very light, because the weight sits on a long lever. Our guide to weighted ab exercises covers how to add load safely.
Sets, reps and where to put it
For most people, 2-4 sets of 8-15 reps works well, finishing each set a rep or two short of failure. If you can easily exceed 20 reps, progress to a harder variation rather than just adding more reps.
Place reverse crunches early in your ab session when you're fresh, since they need control. A simple pairing:
- Reverse crunch: 3 x 10-15
- Cable crunch or weighted crunch: 3 x 10-12
- Side plank: 2 x 30 seconds per side
That covers lower abs, upper abs and obliques in about 12 minutes. For more on how much to do, see sets and reps for abs, or plug your equipment into the ab workout generator.
Reverse crunch vs leg raise
Both are popular lower-ab exercises, but they load you differently.
- Reverse crunch: short lever, bent knees, the ab work comes from curling the pelvis. Easier to learn and gentler on the lower back.
- Lying leg raise: long lever, straight legs, lots of hip flexor involvement. More demanding to keep the back flat.
Beginners usually do better starting with reverse crunches, then adding leg raises once the pelvic tilt is automatic.
Will reverse crunches give me visible lower abs?
They'll help build the muscle, but whether you can see it depends on body fat. Lower belly fat is often the last to go, and no exercise burns fat in one specific spot. Pair your training with a steady calorie deficit and enough protein. The TDEE calculator is a good starting point for working out how much to eat.
Safety notes
If you feel pinching in your lower back or neck, reduce the range and slow down. Keep your head on the floor and your neck relaxed. If you have back pain, a hernia, are pregnant or postpartum, or suspect diastasis recti, check with a doctor or physical therapist before doing flexion exercises like this one.
Where AbShred fits
AbShred is an iPhone app on the way that scores your Lower Abs as one of six zones from a single photo. If that turns out to be your weakest area, your weekly plan starts there, with exercise demos for moves like this one. It's an AI estimate for motivation, not a medical measurement. Join the waitlist at abshred.com.
FAQ
Are reverse crunches better than regular crunches?
Neither is better overall. They emphasize different ends of the same muscle. Regular crunches bias the upper portion and reverse crunches bias the lower portion, so doing both is a sensible approach.
How many reverse crunches should I do?
Two to four sets of 8-15 slow reps is a good range. If you can do more than 20 with good form, make the exercise harder instead of adding reps.
Why do I feel reverse crunches in my hip flexors?
You're probably pulling your knees in without lifting your hips. Focus on rolling your tailbone off the floor, and slow down. Some hip flexor feeling is normal because they hold your legs in position.
Can I do reverse crunches every day?
You can do a few easy sets daily, but if you're taking sets close to failure, two to four sessions a week with rest days in between will give better results.
Are reverse crunches safe for lower back pain?
Many people tolerate them well because the lever is short and the movement is controlled, but back pain has many causes. If you have pain, ask a physical therapist which core exercises suit you.