Reverse Crunch
The reverse crunch is a floor exercise in which you lie on your back with your knees bent and curl your hips up off the floor towards your ribs. It works the abdominals, with a bias towards the part of the six-pack muscle below the belly button, and needs no equipment.
Also called: Reverse Sit-Up, Reverse Curl-Up, Hip Curl, Pelvic Tilt Crunch · Equipment: bodyweight · Pattern: isolation
Step by step
- Lie on your back on a mat with your arms flat by your sides, or hold a fixed object behind your head for anchorage.
- Lift your legs so your thighs are vertical and your knees are bent to about 90°, with your shins roughly parallel to the floor.
- Breathe out and tilt your pelvis backwards, as if rolling your pubic bone towards your belly button, so the small of your back presses into the floor.
- Keep curling so your hips peel a few centimetres off the floor and your knees travel slightly towards your chest. The movement is small; the lift comes from the tilt, not from swinging the legs.
- Pause briefly at the top without rocking back towards your head.
- Uncurl slowly, bringing your hips back to the floor under control while the small of your back stays in contact with the mat.
- Reset your knees over your hips and start the next rep from a still position.
- Roll your pubic bone towards your ribs
- Press the small of your back into the floor
- Lift your hips with your abs, not your legs
- Small and slow, no swing
- Knees stay bent at 90°
- Breathe out as your hips curl up
In VALDA, these cues are one tap away on the exercise while you train.
What it trains
| Muscle | Role | Evidence |
|---|---|---|
| Rectus abdominis: lower | Prime mover | C |
| Rectus abdominis: upper | Secondary | C |
| Obliques (internal/external) | Secondary | C |
| Hip flexors | Secondary | C |
| Transverse abdominis | Stabiliser | C |
Evidence grades: A = strong research base · B = good · C = limited · D = coaching consensus.
What goes wrong, and the fix
Swinging the legs up
Fix: Start each rep with the pelvic tilt and keep the movement small.
Rocking and bouncing
Fix: Pause with your hips on the floor and start each rep from still.
Back arching as the hips come down
Fix: Uncurl slowly and finish each rep with the small of your back on the mat.
Throwing the knees overhead
Fix: Curl only until your hips leave the floor, then come back down.
Straightening the legs
Fix: Keep your knees bent at about 90° throughout the set.
Holding the breath
Fix: Breathe out steadily as your hips curl up.
What the research says
Muscle growthGeneral fitnessEndurance
- Effort and reps — Research finds muscle growth is similar across a wide range of loads when sets are taken close to failure. At bodyweight, many lifters use sets of about 10–20 slow reps and move to a cable or decline version once those feel easy.
- Proximity to failure — Studies show growth rises as sets get closer to failure, but true failure adds only a small extra benefit over finishing a few reps short.
- Volume and frequency — Research links more weekly sets for a muscle to more growth, with diminishing returns. Training a muscle about twice a week is associated with more growth than once, largely because it adds weekly sets.
- Tempo — Rep durations of about 0.5 to 8 seconds have produced similar growth when sets are hard. A slow uncurl is a common way to keep the abdominals working through the whole rep.
- Regional emphasis — EMG research finds pelvic-tilt movements bias the part of the six-pack muscle below the belly button in trained, skilled performers, but this is activation, not growth. There is no training study comparing reverse crunches with standard crunches for muscle growth.
Swap it mid-workout
With VALDA Pro, FLEX offers alternatives like these when you swap an exercise mid-workout.
Log the reverse crunch in VALDA, with these cues one tap away while you train and your history for it in one place.
General information about exercise technique, not medical advice. If you have an injury or a health condition, your healthcare provider is the right person to ask.