Reverse Crunch with Leg Extension

Also known as: reverse crunch leg extension, reverse crunch with leg extensions, lying bottoms up, bottoms up crunch, straight leg reverse crunch, Leg Extension Reverse Crunch

In SetGrip: Reverse Crunch (Leg Extension)

Secondary muscles
Obliques, Hip Flexors
Body part
Core
Position
Lying
Laterality
Bilateral (both sides together)
Category
Strength

Track this exercise in SetGrip — no account needed

Instead of keeping the knees tucked, this reverse crunch finishes with the legs driving toward the ceiling as the hips leave the floor, which lengthens the lever right at the hardest point. Lower in two stages - hips down first, then knees - and the obliques pick up a stabilizing role the standard Reverse Crunch never asks of them.

How to do the Reverse Crunch with Leg Extension

  1. Lie flat on your back with your legs extended and your arms by your sides.
  2. Bend your knees and bring them towards your chest, keeping your feet off the ground.
  3. Engaging your abs, lift your hips off the ground, bringing your knees towards your head.
  4. Pause for a moment at the top, then slowly lower your hips back down to the starting position.
  5. Repeat for the desired number of repetitions.

Tip: Breathe out as you crunch and let the last bit of air leave the lungs at the top of each rep.

Muscles worked

Primary

Abs · Core

The rectus abdominis shortens to bend the spine forward, and each rep should end with the upper abs fully contracted and the ribs pulled down.

Secondary

  • Obliques — Twisting or side crunch variations bring the obliques in, and you should feel them along the side of the waist on the working side.
  • Hip Flexors — The hip flexors take over if your feet are anchored and you come up too high; keep the range short to leave them out.

Common mistakes

  • Pulling on the neck — hands behind the head should support, not yank; keep the elbows wide and the chin about a fist away from the chest.
  • Sitting all the way up — a crunch is a curl of the ribs toward the pelvis, not a sit-up; the lower back should stay on the floor the whole time.
  • Cranking out fast reps — momentum does the work if you bounce; lift to a squeeze, hold for a count and lower slowly.
  • Never adding load — once bodyweight reps get easy, hold a plate on the chest or use a cable rather than doing sets of 50.

Sets, reps and where it fits

GoalSets × repsRest
Strength3 × 8–1260 s
Endurance2–3 × 15–2545 s

Crunches close out a session after the heavy work, or they can fill the rest periods between sets of a lift that does not need much bracing. Pair a cable crunch with a cable side bend on the same stack.

Variations and alternatives

Similar exercises

Without bodyweight

Easier and harder

Frequently asked questions

What muscles does the Reverse Crunch with Leg Extension work?

The Reverse Crunch with Leg Extension primarily works the abs. It also involves the obliques and hip flexors, which assist the movement and stabilise the joints.

Is the Reverse Crunch with Leg Extension good for beginners?

It is rated intermediate, so it suits people who already train regularly. Beginners can still do the Reverse Crunch with Leg Extension with light load and a spotter or coach watching the first few sessions; if it feels awkward, pick an easier variation from the alternatives below first.

What can I do instead of the Reverse Crunch with Leg Extension?

If you cannot do the Reverse Crunch with Leg Extension, try the Banded Bicycle Crunch, the Twisting Hip Lift Hanging Leg Raise or the Arms Overhead Crunch. Each of them trains the abs through a similar movement, so you can swap them in without changing the rest of the workout.

How many sets and reps should I do?

It depends on your goal. For the Reverse Crunch with Leg Extension, a sensible starting point is strength: 3 × 8–12 with 60 s rest; endurance: 2–3 × 15–25 with 45 s rest. Train it at the end of a session or pair it with a lower-body lift as active rest.

Track the Reverse Crunch with Leg Extension in SetGrip

All 1,100+ exercises with animations are in the app. No account, no sign-up — your data stays on your iPhone. Works with Apple Watch.

More exercises

Exercise data and animations are licensed ExerciseDB content used in SetGrip. This page is for general information and is not medical or coaching advice.