Training guide
A reverse crunch is a crunch from the bottom up. Lying on your back with your hips and knees bent at right angles, you curl your pelvis towards your ribs so your hips lift a little off the floor, then lower slowly. Your six-pack muscle and obliques do the curling; swinging your legs hands the work to your hip flexors.
In muscle activity studies it worked the six-pack about as hard as a crunch and the obliques harder, but it doesn't single out your lower abs, and no trial has tested it as a training programme on its own.
This guide shows you how to do it without swinging, how many to do, and the steps up to a decline bench, a cable, the captain's chair and hanging knee raises. It covers what reverse crunches work, the lower abs question, how they compare with crunches and leg raises, and your lower back, osteoporosis, pregnancy and the months after a birth, with a 3D demo of each version.
Lie on your back with your hips and knees bent to right angles and curl your pelvis towards your ribs, so your hips lift a little off the floor, then lower slowly. Keep the same bend in your knees, and don't let them pass your hips on the way back.
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In a study commissioned by the American Council on Exercise (ACE), it worked the six-pack about as hard as a basic crunch and the obliques far harder. On an incline it was among the most demanding ab exercises measured.
The six-pack works as one muscle. Some studies found a little more activity in its lower part when the pelvis moves, others none.
2 to 3 sets of 8 to 15 slow reps, stopping 2 or 3 reps short of failure, 2 or 3 days a week, and a harder version once 3 sets of 15 are smooth, as our hanging leg raise progression does. Count them towards about 60 bending reps a session, as our get abs guide advises.
No study has measured spine load in a reverse crunch. It rounds your lower back with every rep, so keep the reps controlled, ease off if repeated bending flares your back, and leave it out with osteoporosis.
Reverse crunches build the muscle, but exercising your abs doesn't remove the fat over them. Fat comes off with your overall activity and eating.
Instead of curling your ribs towards your pelvis, you curl your pelvis towards your ribs. From a tabletop (hips and knees at right angles), your hips lift a little off the floor as your lower back rounds, then lower again. ACE rates it intermediate, a step above the basic crunch, and puts the emphasis on "pulling your pelvis upwards towards your rib cage".
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The six-pack muscle (rectus abdominis) and the obliques curl your pelvis, with the deepest tummy muscle (transversus abdominis) working underneath. Your hip flexors hold your legs up and join in more if you swing.
The floor reverse crunch; the bent-knee hip raise, which starts with your feet low; the vertical-leg hip raise, with straight legs; the decline bench reverse crunch; the cable reverse crunch; the captain's chair knee raise; and the hanging knee raise, each with a 3D demo. A reverse crunch machine has no demo of its own: it's the same curl with a pad and a weight stack.
The numbers on this page come from EMG (electromyography: electrodes measuring how hard a muscle works over a few reps). They show effort, not what a muscle will build.
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In ACE's study of 13 ab exercises in 30 adults, the reverse crunch worked the six-pack at 109% of a basic crunch (the study counted only 125% or more as clearly better) and the obliques at 240%, third of the 13. The study wasn't peer reviewed. In 25 adults, the reverse curl gave the most lower six-pack activity of 5 exercises and, with the V-sit, the most outer oblique activity.
In 21 adults, the reverse crunch on a 30-degree incline was among the most demanding exercises for the upper and lower six-pack and the internal oblique, with quiet lower back muscles but high activity in the rectus femoris, a hip flexor. The authors warn that this hip flexor activity "may be problematic for some people with low back problems".
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In 10 people, the vertical hip lift (knees bent, hips lifted until the lower back leaves the floor, much like the top of a reverse crunch) was the most demanding of 12 trunk exercises, with six-pack peaks of 80 to 100% of maximum.
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In 9 women, moving the pelvis rather than the ribcage raised oblique activity in most of the tasks tested.
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A review of 87 studies found that inclines and added load raise how hard ab exercises work. The captain's chair worked the six-pack at 212% of a crunch and the obliques at 310% in ACE's study, and the hanging straight-leg raise passed 130% of maximal six-pack activity in 14 men.
No trial has tested reverse crunches on their own as a training programme, and no study has measured the load on the spine during one. What we know comes from muscle activity studies of a few reps in healthy adults.
From ACE's reverse ab crunch and our move page. Breathing out as you curl is ACE's cue.
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The movement on the figure: Reverse crunch
From our move page. Stop your feet higher if your lower back lifts off the floor as they lower.
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The movement on the figure: Bent-knee hip raise
In 11 lean adults, and in 8 adults doing 6 exercises, the upper and lower parts of the six-pack worked alike; in the second study, curl-ups worked both parts harder than the reverse curl-up. In 33 adults, a pelvic tilt (flattening your lower back) worked the lower part harder than a curl-up, but only in trained people doing it correctly, and in 25 adults the reverse curl gave the most lower six-pack activity of 5 exercises. On ultrasound in 15 students, the part nearest the moving load changed most, but crunches worked the whole muscle 36% more than leg raises. ACE's authors concluded the parts act "as a sheath".
So you can shift the emphasis a little, but you can't train your lower abs on their own, as our hanging leg raise guide also says.
The hip flexors work whenever the hip bends to lift the legs, and the inclined reverse crunch showed high rectus femoris activity. Curl your pelvis rather than swinging your knees, so your abs, not your hip flexors, do most of the work.
Move up once 3 sets of 15 are smooth, as our hanging leg raise progression says. Heel taps if you need them first, 2 to 3 sets of 6 to 10 each side (our 30-day ab challenge); the floor reverse crunch, 2 to 3 sets of 8 to 15 (our 30-day ab challenge and hanging leg raise progression); the bent-knee or vertical-leg hip raise, 2 to 3 sets of 10 to 15 slow reps (their move pages' dose, editorial); the decline reverse crunch, 2 to 3 sets of 8 to 12, and the cable reverse crunch, 2 to 3 sets of 10 to 12, adding weight once 12 is easy (our editorial starting points); then the captain's chair and the hanging knee raise, 2 to 3 sets of 8 to 12 (our hanging leg raise progression).
3D demoDead bug heel tapsBeginner · No equipment
3D demoReverse crunchIntermediate · No equipment
3D demoBent-knee hip raiseIntermediate · No equipment
3D demoVertical-leg hip raise (bottoms up)Intermediate · No equipment
3D demoDecline reverse crunchIntermediate · A bench or box
3D demoCable reverse crunchIntermediate · A cable machine
3D demoCaptain's chair knee raiseIntermediate · Other / check instructions
3D demoHanging knee raiseIntermediate · Pull-up bar2 to 3 sets of 8 to 15, as our 30-day ab challenge and hanging leg raise progression use, or 10 to 12 in a circuit, as our no-equipment ab workout does.
Stop each set 2 or 3 reps short of failure, or 3 or 4 short in your first two weeks, as our plans advise, and end it when you start to swing. Going to failure adds little, and people underestimate the reps they have left by about 1.
45 to 60 seconds between sets, as the curl block of our 30-day ab challenge uses.
2 or 3 days a week, with 2 or 3 ab moves in a session, as our get abs guide suggests. Matched for weekly sets, training a muscle more often makes little difference to growth.
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Keep crunches, sit-ups and other bending moves, reverse crunches included, to about 60 reps a session, as our get abs and sit-up guides advise: one expert review's suggestion, untested. Make them harder rather than doing more.
Reps up to 15, then a slower lowering (about 3 seconds), then the next step on the ladder (our editorial order, following our plans' advice for body-weight moves).
We found no study of spine load in a reverse crunch. In 9 volunteers, no single ab exercise trained every ab muscle with a low load on the spine; the hanging straight-leg raise reached about 3,000 newtons of compression in 14 men; and in pig spines, many thousands of bending cycles under load produced disc herniations. A sensible number of controlled reps suits most healthy backs, in our reading.
Core exercise helped chronic low back pain against minimal treatment, but no more than other exercise, and exercise of any kind lowered pain by about 15 points out of 100. Reverse crunches aren't a back pain treatment; choose what you'll keep doing.
An aching lower back usually means you're swinging or lowering too far: shorten the range, slow down, or go back a step, as our hanging leg raise progression says. Discomfort up to about 5 out of 10 that settles within an hour or so and is no worse the next morning is acceptable, as our back pain guides say. Stop if bending forward sends pain down a leg.
A UK consensus advises modifying or avoiding "sustained, repeated or end-range flexion", so leave reverse crunches out with osteoporosis or a past spinal fracture, as our 30-day ab challenge and hanging leg raise progression do. Dead bugs, Pallof presses and carries train your abs without bending.
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Pull your pelvis up towards your ribs rather than swinging your knees, as our move page cues.
Stop with your knees over your hips, as ACE advises.
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Keep the same right angle at the knee all the way through.
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Lower one part of your back at a time.
Use your arms lightly, for balance (our editorial cue).
Count them in your 60 bending reps, and make the move harder rather than doing more.
Both work the whole six-pack; the reverse crunch worked the obliques harder in ACE's study and spares your neck, so it's a good swap if crunches make your neck ache, as our crunch and sit-up workout suggests.
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In 20 students, a lying leg raise worked the hip flexors more and the six-pack less than a sit-up. The reverse crunch keeps your knees bent and adds the pelvic curl, and it's the first step towards hanging leg raises in our progression.
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The hanging leg raise is much harder: over 130% of maximal six-pack activity in one study. The captain's chair and hanging knee raises sit between them, as our hanging leg raise guide sets out.
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The dead bug keeps your spine still and your back resting on the floor; the reverse crunch bends it. If bending flares your back, or you have osteoporosis, the dead bug is the better choice, as our dead bug guide explains.
In later pregnancy the NHS advises against lying flat on your back for more than a few minutes, which it says "can make you feel dizzy and is not good for your baby". Our rule starts after the first trimester: swap reverse crunches for the half-kneeling Pallof press or bird dogs, as our pregnancy workouts do.
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Not in the first weeks: the NHS advises avoiding "sit-ups, planks and high-impact exercises to start with". Start with its gentle tummy exercises and our diastasis recti guide's stages, and add reverse crunches once stage 2 is easy and the middle of your tummy doesn't dome (our editorial reading). In a trial of 70 women with a gap between the tummy muscles, 12 weeks of curl-ups didn't widen the gap; reverse crunches weren't tested.
After abdominal or bowel surgery, or with a stoma, leave reverse crunches out while your tummy heals, as our move page says: UK stoma and hospital leaflets advise against sit-ups and double leg raises at first. Stop if you notice bulging around a scar or stoma. With a hernia, leave out any core move that makes it bulge, as our hernia guide advises.
The NHS advises avoiding activities that put a lot of strain on the pelvic floor, like heavy lifting, running and trampolining. Our crunch and sit-up workout skips its crunch and sit-up tracks, reverse crunches included, with a prolapse or leaking, and our oblique workout swaps its twist and crunch for more Pallof presses with a prolapse.
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Your head stays down in a reverse crunch; if your neck aches, you're probably lifting it.
McGill curl-ups, 2 to 3 sets of 5 holds of 8 to 10 seconds, and dead bugs, 2 to 3 sets of 6 to 10 each side (our 30-day ab challenge, session A); half-kneeling Pallof presses, 2 to 3 sets of 8 to 10 each side, and side planks, 2 to 3 holds of 15 to 40 seconds each side (session B); glute bridges, 12 reps (our beginner core workout); and the half-kneeling hip flexor stretch, 30 seconds each side (our hanging leg raise progression).
Core session A of our 30-day ab challenge brings reverse crunches in on its harder track; the hanging leg raise progression starts with them and takes you to the bar; the no-equipment ab workout, the crunch and sit-up workout and the dragon flag progression use them too.
A 12-minute core session for the front of the trunk: dead bugs, curl-ups or crunches and front planks, each with steps from beginner to harder.
12 minBeginner11 movesNo equipmentA 25-minute ladder to hanging leg raises: reverse crunches, the captain's chair, hanging knee and straight-leg raises, then strict toes to the bar.
25 minBeginner10 movesPull-up bar, A stepAn intermediate ab workout with no equipment: planks, side planks, reverse crunches, hollow holds and mountain climbers.
20 minIntermediate7 movesNo equipmentA 15-minute ab workout with a crunch track and a sit-up track, about 60 bending reps at most, plus a side plank and bird dog to balance it.
15 minBeginner10 movesNo equipmentBuild to a dragon flag: dead bugs, hollow holds, reverse crunches and bench leg raises, then tucked, one-leg and full dragon flag lowerings.
25 minAdvanced6 movesA bench or boxThe 30-day ab challenge uses core session A; the calisthenics plan uses our full-body bodyweight workout, which has reverse crunches in its circuit.
A free 30-day ab challenge: four 12-minute core sessions a week, from dead bugs to hollow holds, with rest days and an honest word on belly fat.
4 training days12 minBeginner3 days a weekA 12-week calisthenics plan for beginners: three bodyweight sessions a week with push-up, pull-up, squat and dip ladders, and a bar if you have one.
3 training days40 minBeginnerIf you get chest pain or pressure, feel faint or dizzy, are unusually breathless, or your heart races or beats irregularly during exercise, as our plans advise. The American Heart Association says these need immediate medical evaluation.
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For chest pain that feels tight, heavy or squeezing, or spreads to your arms, neck, jaw or back; a headache that starts suddenly and is extremely painful; someone who faints while exercising; palpitations that don't go away, or come with chest pain, breathlessness or feeling faint; severe difficulty breathing; or angina pain that doesn't stop after rest and your medicine. Don't drive yourself to A&E.
If you haven't exercised for some time or have a medical condition, speak to your GP first, as the NHS advises. Breathe out as you curl; never hold your breath.
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See a GP after any faint, and for dizziness that won't go away or keeps coming back.
Loss of feeling or numbness around the genitals or bottom, new trouble peeing or controlling your bladder or bowels, changes in genital sensation during sex or problems with erections or orgasm, or pain, tingling, weakness or numbness in both legs. These are signs of cauda equina syndrome, which needs treating in hospital urgently. Don't drive yourself.
With a high temperature, or if you feel hot, cold, shivery or generally unwell, or if severe pain starts suddenly or gets worse quickly. In the US, use urgent care.
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Back pain that doesn't improve after a few weeks of treating it at home, stops your day-to-day activities, is worse at night or after resting, or comes with weight loss you can't explain or a lump or change in the shape of your back.
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A sudden sharp pain in your tummy muscles during a set may be a strain: see our pulled stomach muscle guide. Get help from NHS 111 (in the US, urgent care) if it's very painful or getting worse, there's a lot of swelling or bruising, or it isn't getting better after treating it yourself.
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See a GP if you think you have a hernia: a bulge or lump in your groin, upper thigh or tummy that may get bigger when you cough, sneeze or cry and smaller when you lie down. Get help from NHS 111 if you have a hernia and pain in or around it, a bloated tummy, sickness, constipation, a high temperature or sudden confusion. Call 999 or go to A&E for a femoral hernia (a lump at the top of the thigh) with very bad tummy pain, sickness, being unable to fart or poo, a high temperature or sudden confusion.
The six-pack is one muscle. Some studies found a little more activity in its lower part when the pelvis moves, others none, and crunches still worked the whole muscle more than leg raises on ultrasound. You can shift the emphasis; you can't isolate it.
Some health pages say research shows this, but we found no study that measured spine load in a reverse crunch. Both bend the lower back, and the inclined version showed high hip flexor activity that researchers say may be a problem for some people with low back problems. Keep reps controlled and ease off if your back complains.
The hip flexors join in, but done as a curl, the reverse crunch worked the six-pack as hard as a crunch and the obliques harder. Swinging your legs is what hands the job to your hip flexors.
Ab exercises don't remove the fat over them: 6 weeks of ab exercise changed no fat measure in 24 adults, adding ab training to a diet did no better than the diet alone in 40 women, and across 13 studies training one area didn't reduce the fat there. Our belly fat guide covers what does help.
Your whole six-pack muscle and your obliques, with your hip flexors helping. In ACE's study they worked the six-pack about as hard as a crunch and the obliques far harder.
Not on their own: the six-pack works as one muscle. Some studies found a little more activity in its lower part when the pelvis moves, others none.
2 to 3 sets of 8 to 15, stopping 2 or 3 reps short, as our 30-day ab challenge and hanging leg raise progression use. Move to a harder version once 3 sets of 15 are smooth, and keep all your bending reps to about 60 a session.
Usually because you're swinging, lowering too far or doing too many. Curl your pelvis rather than swinging your knees, stop with your knees over your hips, and go back to dead bugs if it still aches; if the pain lasts or spreads down a leg, see our back pain guide.
Neither is better overall: both work the whole six-pack. Reverse crunches worked the obliques harder in ACE's study and spare your neck, so they're a good swap if crunches make your neck ache.
The reverse crunch is the first step towards hanging leg raises; the captain's chair and hanging knee raises come next. Straight-leg raises lying down lean more on the hip flexors and need your lower back to stay down.
Slow the lowering to about 3 seconds, then use a decline bench, a cable at your ankles, the captain's chair or a hanging knee raise. Inclines and added load raise the work for your abs.
Learn them on the floor. A decline bench makes them harder, and you hold the bench behind your head for balance.
Not in the first weeks: start with the NHS's gentle tummy exercises and our diastasis recti guide's stages. Once stage 2 is easy, they're reasonable if the middle of your tummy doesn't dome; in a trial, curl-ups didn't widen the gap.
After the first trimester, the NHS advises against lying flat on your back for more than a few minutes, so swap them for the half-kneeling Pallof press or bird dogs. At any stage, stop if you feel uncomfortable, too hot or unwell, as the NHS advises.
No. They build the muscle, but exercising a body part doesn't remove the fat over it.
Leave them out: a UK consensus advises modifying or avoiding repeated or end-range bending of the spine. Dead bugs, Pallof presses and carries train your abs without it.
Exercise education, not a personal prescription, and clinical review of these guides is pending. Check with a GP before starting hard training if you have a heart condition, chest pain, dizziness or breathlessness when active, and stop for sharp or increasing pain. Health disclaimer.
