RIRLift app icon RIRLift

Exercises

Reverse crunch: how to do it right and what it works

Published October 19, 2026

A reverse crunch is an ab exercise where you lie on your back and curl your hips up off the mat toward your ribs, instead of lifting your shoulders as in a normal crunch. Start with bent knees and thighs vertical, roll your tailbone up using your abs, then lower slowly until your lower back is flat again. The rep is the pelvis curling, not the legs swinging.

Your last reverse crunch set

How to do the reverse crunch

Most ab work moves the ribcage down toward the hips. The reverse crunch moves the hips up toward the ribcage, which keeps your head and neck on the floor and trains the abs through the part of the curl that tucks the pelvis. It needs nothing but a mat and is easy to make harder by slowing it down or straightening the legs.

Steps

  1. Lie face up on a mat, arms flat along the floor beside you, and bring your knees up so your thighs point at the ceiling and your knees are bent about square.
  2. Press your lower back gently into the floor and breathe out.
  3. Use your abs to roll your tailbone and then your lower back off the mat, bringing your knees in toward your chest without changing the bend in them.
  4. Stop when your hips are fully curled and your weight sits on your upper back, pausing for a beat.
  5. Unroll one vertebra at a time until your tailbone touches down, keeping your thighs vertical before the next rep.

Cues

  • Curl the tailbone, not the knees
  • Knee angle stays fixed
  • Slow on the way down

Common mistakes

  • Swinging the legs to throw the hips up: if you need momentum, shorten the range and pause at the bottom of each rep.
  • Pushing hard through your hands to lift: keep your arms relaxed so the abs do the lifting.
  • Dropping the legs toward the floor between reps: stop with your thighs vertical, where the abs still hold tension.

Swap for: Hanging Knee Raise, Crunch, Dead Bug

Muscles the reverse crunch works

The reverse crunch works your rectus abdominis, the long six-pack muscle down the front, with a lot of the effort felt low in the belly because the pelvis is the part that moves. Your obliques and the deep transverse abs help, and your hip flexors hold the legs in place.

Sets, reps and reps in reserve for the reverse crunch

GoalSets × repsRIRRest
Build the abs 3 × 10–15 1–2 60 s
Add a 2-second lowering once 15 clean reps feel easy.
Learning the curl 2–3 × 8–10 3 60 s
Hold a short pause at the top so you feel the pelvis tuck before adding reps.
Finisher after heavy lifting 2 × 12–20 0–1 45–60 s
Pair with a plank or dead bug at the end of the session.

Reverse crunch variations

  • Lying Knee Raise start position

    Lying Knee Raise

    Bring the knees in without lifting the hips when the full curl is still too hard.

    Build a session with it
  • Decline Crunch start position

    Decline Crunch

    Sit up on a decline bench when you want a harder, longer ab curl than the floor gives.

    Build a session with it
  • Hanging Knee Raise start position

    Hanging Knee Raise

    Hang from a bar and curl the knees up when floor reps reach 20 and you want a harder version.

    Build a session with it

Reverse crunch alternatives

Floor ab work

  • Crunch start position

    Crunch

    Lift your shoulders instead of your hips when you want the opposite end of the same muscle.

    Build a session with it
  • Dead Bug start position

    Dead Bug

    Keep the lower back flat while the arms and legs move when you want control over curling.

    Build a session with it

Loaded ab work

Reverse crunch vs regular crunch

Both train the same abs by rounding your spine. A regular crunch lifts your shoulders toward your hips; a reverse crunch lifts your hips toward your shoulders. The reverse version keeps your neck out of it and feels lower in the belly, while the crunch feels higher. Doing both covers the whole curl, and neither one burns fat from a particular spot.

Will reverse crunches flatten your stomach?

They build the ab muscle, but they do not burn the fat over it. Visible abs come from lower body fat, which depends on eating and your overall training. Use reverse crunches to make the muscle stronger and thicker, and expect it to show as you get leaner.

Questions

What muscles do reverse crunches work?

Mainly the rectus abdominis, felt most in the lower part, with help from the obliques and the deep abs. The hip flexors hold your legs but should not do the lifting.

Are reverse crunches good for lower abs?

Yes. The rectus abdominis is one muscle, but curling the pelvis up puts more of the effort low in the belly, which is why most people feel them there.

Why do I feel reverse crunches in my hip flexors?

You are probably swinging your knees toward your chest instead of curling your tailbone up. Keep the knee angle fixed and only count reps where your hips leave the floor.

How many reverse crunches should I do?

Two to three sets of 10 to 15 slow reps, stopping one or two reps before you would need to swing, is enough for most people two or three times a week.

Will 100 crunches a day lose belly fat?

No. Crunches of any kind train the muscle, not the fat over it. A few hard sets a few times a week builds the abs as well as 100 easy reps a day.

What equipment do you need for a reverse crunch?

Just a mat. A bench or decline bench lets you hold on overhead and increase the range once floor reps get easy.