Training guide
Flutter kicks are an ab exercise you do lying on your back: with your legs straight and lifted, you make small, quick up-and-down kicks while your lower back stays still on the floor. The height of your legs is the dial: high is easier, low is harder, and the moment your lower back lifts, the set is over.
No study has tested flutter kicks themselves. What we know is borrowed from studies of lifting and lowering both legs: keeping your lower back down makes your abs work harder, your hip flexors do much of the moving, and most people's lower back starts to arch early as their legs go down.
This guide shows you how to set your back, where to start your legs, and the steps from heel taps and dead bugs to low flutter kicks and the hollow position. It covers what flutter kicks work, how long to do them, why they can hurt your lower back, how they differ from scissor kicks, and who should change them, with a 3D demo and a follow-along progression.
Lie on your back, let your lower back rest on the floor, lift both straight legs and make small, quick, alternating kicks from your hips. Your lower back stays down the whole time: when it starts to lift, the set is over. In a study of a similar straight-leg lift, a flat lower back made the six-pack work harder than an arched one.
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The higher your legs, the easier. Start high, near vertical if you need to (our editorial starting point), and lower them over the weeks only as far as your back stays down. In one study, the lower back began to arch almost as soon as the legs started to lower.
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The evidence is borrowed from studies of lifting and lowering both legs, the closest movements. In those, legs hovering off the floor worked the six-pack about twice as hard as heels resting on it, and lowering both legs with the lower back held flat worked the abs harder than a curl.
Your hip flexors lift and kick your legs; your abs hold your pelvis still. That's normal, and an aching front of the hip means your legs are too low for now.
2 to 3 sets of 20 to 30 seconds, ending each set when your lower back starts to lift (our scissor kick move page's dose, an editorial starting point). Kick steadily: in one study, faster or slower leg movements didn't change how hard the abs worked overall. Make it harder, not longer.
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Flutter kicks train the muscles, but exercising your abs doesn't remove the fat over them. Fat comes off with your overall activity and eating.
Lying on your back with straight legs lifted off the floor, you make small, quick, alternating up-and-down kicks from your hips, a few inches each way, while your lower back stays still on the floor. Your legs are long levers: your abs hold your pelvis and lower back still while your hip flexors move and hold your legs.
The six-pack muscle (rectus abdominis), the obliques and the deepest tummy muscle (transversus abdominis) hold your pelvis and lower back still. The hip flexors (the iliopsoas, rectus femoris and sartorius) lift and kick your legs, and your thigh muscles keep your knees straight.
No 3D demo shows the face-up flutter kick. The demo on this page is scissor kicks, the same position with bigger kicks, and it starts lower than we'd suggest, with the heels about 6 inches off the floor. For flutter kicks, keep the kicks small and quick, and start with your legs higher.
You should be able to do dead bug heel taps with your lower back still, as our scissor kick move page asks. If you can't yet, start there: it's step 1 of the ladder below.
Longer, heavier legs are bigger levers, so the same height is harder (our editorial reading). Most people's lower back starts to arch early as the legs lower, so the height where yours lifts is personal: work where it stays down.
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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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We found no study of muscle activity, spine load or training effects in the face-up flutter kick. The studies that named flutter kicks were about swimming, or listed them as one item in a programme. Everything below is borrowed from studies of lifting and lowering both legs.
In 16 men holding both straight legs about 5 cm off the floor, tilting the pelvis back (flattening the lower back) raised upper and lower six-pack activity against tilting it forward into an arch; a neutral pelvis did as well as the tilt back, and hip flexor (rectus femoris) activity didn't change. In 15 men, lowering both straight legs with the pelvis held tilted back worked the abs harder than a bent-knee curl.
In 22 young men doing the Sahrmann core test (five levels of leg movements, each harder than the last), six-pack activity was a median of 35.7% of maximum with both legs hovering about 12 cm off the floor as they straightened, against 18.2% with the heels sliding on the floor, and 26.4% against 17.2% with one leg. A double-leg-lowering test also tracked six-pack activity and the load at the hip in 10 adults.
In 17 healthy adults lowering both straight legs from vertical, the pelvis had started to tip forward (arching the lower back) by the time the legs had come down an average of 3.6 degrees, whether or not they tried to stop it, and it tipped further as the legs went lower. So start with your legs high, and lower them only as far as your back stays down.
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In 6 men, lifting both legs, but not one, needed the abs, and leg lifts worked two hip flexors (the iliacus and sartorius) hard. In 20 students, a leg raise worked the iliopsoas and rectus femoris more than a sit-up, and the six-pack less (about 21% of maximum against 28%). Across 9 studies, the iliopsoas worked hardest between 30 and 60 degrees of hip bend, above 60% of maximum in leg raises.
In 16 men, moving the legs over 1, 3 or 5 seconds in one level of the Sahrmann test changed when the abs switched on, but not how hard they worked overall. Steady, controlled kicks are enough.
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Our editorial steps, from our scissor kick move page. The demo shows scissor kicks, the same position with bigger kicks, starting with the heels about 6 inches off the floor; most people should start with their legs higher than that.
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The movement on the figure: Scissor kicks
From our heel taps move page. Then dead bugs, as our dead bug guide teaches.
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The movement on the figure: Dead bug heel taps
From our leg pull-in move page; it's the fifth level of the Sahrmann core test.
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The movement on the figure: Leg pull-in
We found no study of spine load in flutter kicks. In 22 adults, a lying double leg thrust gave high rectus femoris activity, which the authors say could be a problem for people with low back problems, and researchers gave the same caution for an inclined reverse crunch. The nearest load data come from other ab exercises: in 9 volunteers, no single ab exercise trained every ab muscle with a low load on the spine, and the hanging straight-leg raise reached about 3,000 newtons of compression in 14 men.
An aching lower back in flutter kicks almost always means it's arching: raise your legs, bend your knees, or go back to heel taps, as our scissor kick move page says. Most people's lower back starts to arch early as the legs lower, so where yours lifts is personal.
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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 it sends pain, pins and needles or numbness down a leg, and stay on heel taps and dead bugs while your back is sore.
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. Flutter kicks aren't a back pain treatment; choose what you'll keep doing.
Move up once every set reaches the top of its range for 2 sessions with your lower back still, as our 30-day ab challenge does. Heel taps and dead bugs, 2 to 3 sets of 6 to 10 each side (our 30-day ab challenge); the leg pull-in, 2 sets of 6 to 8 (our editorial starting point); flutter kicks with your legs high, 2 to 3 sets of 20 to 30 seconds (our scissor kick move page's editorial dose), lowering them a little every week or two while your back stays down; then flutter kicks from the hollow position, 2 to 3 sets of 10 to 30 seconds, knees soft at first (our editorial use of the 30-day ab challenge's hollow hold dose), not with osteoporosis.
2 to 3 sets of 20 to 30 seconds (our scissor kick move page's dose, an editorial starting point), or 10 to 20 seconds to start if that's too much (editorial). If you'd rather count, count each kick of one leg as one.
End each set when your lower back starts to lift, not at a time or a count.
30 to 45 seconds between sets, as the front block of our 30-day ab challenge uses.
2 or 3 days a week, as one of 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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Lower your legs a little, then move to the hollow version, rather than going past about 60 seconds, as our plank guide and 30-day ab challenge advise.
The main one. Raise your legs or bend your knees, as our scissor kick move page says.
Height is the dial: lower them over weeks, not in one session.
Keep them small and controlled; bigger kicks are scissor kicks.
Breathe steadily throughout.
Keep your head down unless you're doing the hollow version.
Make it harder, not longer: lower your legs or move up a step.
Coaching pages use the names loosely, and some call them the same thing. On this site, flutter kicks are small, quick up-and-down kicks; scissor kicks are bigger, with one leg rising to about 45 degrees as the other lowers to just above the floor. Both keep your lower back down, and the same ladder suits both.
The Pilates single straight-leg stretch, often called scissors, curls your head and shoulders up and pulls one leg towards you; it's in the moves below. The Pilates high scissors lifts your hips too, and its move page says to avoid it with a neck problem, osteoporosis or pregnancy.
Face down on a bench with your hips at the end, the kicks work your glutes and hamstrings, not your abs. Keep your legs at about level so your lower back doesn't arch, as its move page says.
The flutter kick that drives you through the water in front crawl is a different subject; this page is about the floor exercise.
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 flutter kicks 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 (heel slides and knee folds, then heel taps), and add flutter kicks once stage 2 is easy and the middle of your tummy doesn't dome (our editorial reading).
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Flutter kicks are a double leg raise, which UK stoma and hospital leaflets advise against at first after tummy surgery or with a stoma, as our hollow body hold and reverse crunch move pages say. Build up through gentler core exercises, and leave out any move that makes a hernia or scar bulge, as our hernia guide advises.
Flutter kicks with your head down keep your spine still. Leave out the hollow version, which curls your upper back: a UK consensus advises modifying or avoiding "sustained, repeated or end-range flexion".
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Aching or cramping there means your legs are too low for now: raise them or bend your knees (our editorial reading). Pain that lasts is covered in our hip flexor pain guide.
The Pilates single straight-leg stretch, 8 to 10 each side, the double straight-leg stretch, 6 to 10 reps, and the hundred, 50 beats building to 100 (their move pages' doses); the bench leg pull-in, 2 to 3 sets of 10 to 15 slow reps (its move page's editorial dose); bird dogs, 1 to 2 sets of 6 each side with 3 to 5 second holds (our crunch and sit-up workout); glute bridges, 12 reps (our beginner core workout); the half-kneeling hip flexor stretch, 30 seconds each side (our hanging leg raise progression); and prone flutter kicks on a bench, 2 to 3 sets of 20 to 30 seconds (its move page's editorial dose), the face-down version for your glutes and hamstrings.
3D demoSingle straight-leg stretch (Pilates scissors)Intermediate · No equipment
3D demoDouble straight-leg stretch (Pilates lower lift)Advanced · No equipment
3D demoHundred (Pilates)Intermediate · No equipment
3D demoBench leg pull-inIntermediate · A bench or box
3D demoBird dogBeginner · No equipment
3D demoGlute bridgeBeginner · No equipment
3D demoHalf-kneeling hip flexor stretchBeginner · No equipment
3D demoProne flutter kicks on a benchBeginner · A bench or boxOur flutter kick progression builds up to flutter kicks step by step, from heel taps; core session A of our 30-day ab challenge has heel taps, dead bugs and the hollow hold in its front block; the 10-minute Pilates abs workout uses the single and double straight-leg stretches.
A 15-minute flutter kick progression: heel taps, dead bugs and leg pull-ins, then flutter kicks with your legs high, lowering them as you get stronger.
15 minBeginner12 movesNo equipmentA 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 equipmentTen minutes of the classic Pilates abdominal series: the hundred, the roll-up and the series of five, with a plank to finish.
10 minIntermediate11 movesNo equipmentThe 30-day ab challenge uses core session A, with its heel taps, dead bugs and hollow holds, for a fuller core routine.
If 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 steadily as you kick; 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 at the front of your hip or in your tummy muscles during a set may be a strain. 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.
Your abs hold your pelvis while your legs move, and keeping your lower back down is what turns them on. The six-pack works as one muscle: some studies found a little more activity in its lower part, others none, so expect at most a small shift in emphasis.
No study has measured it. The problem is the arch: as the legs lower, the lower back starts to arch early, even when people try to stop it. Kicking at a height where your back stays down is the fix; with existing back problems, researchers caution about leg exercises with high front-of-thigh activity.
They move your legs, but lifting both legs needs your abs, and flattening your lower back raised six-pack activity without changing the hip flexor's, as our hollow body hold guide says.
Coaching pages range from sets of 30 to 60 seconds to going past 90 seconds. Our rule is harder, not longer: lower your legs or move up a step before you go past about 60 seconds, as our plank guide advises.
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 abs hold your pelvis and lower back still while your hip flexors move your legs, so you'll feel both. No study has measured flutter kicks themselves; in similar leg-lowering exercises, keeping your lower back down made the six-pack work harder.
Almost always because it's arching: as straight legs lower, the lower back starts to arch early, even when people try to stop it. Raise your legs, bend your knees or go back to heel taps. If back pain lasts, see our back pain guide.
2 to 3 sets of 20 to 30 seconds, stopping as soon as your lower back starts to lift. Make them harder by lowering your legs rather than going past about 60 seconds.
Close, and the names get mixed up. Flutter kicks are small, quick up-and-down kicks; scissor kicks are bigger, with one leg near 45 degrees and the other near the floor. Both keep your lower back down.
They work your whole six-pack, which holds your pelvis still while your legs move. Some studies find a little more activity in the lower part when the pelvis moves, but nothing isolates it.
Start with your legs high, near vertical (our editorial starting point), and small kicks; if that's too much, do heel taps and dead bugs first, as in our flutter kick progression. Lower your legs over the weeks, only as far as your back stays down.
Lower your legs a little at a time, only as far as your back stays down, then do them from the hollow position with your head and shoulders lifted. Going longer isn't the aim: past about 60 seconds, make the position harder instead.
They're related: the hollow hold is the shape, and flutter kicks in that shape are the hardest version. If your back lifts in either, raise your legs.
Not to start: keep your head down so your neck doesn't do the work. Lifting your head and shoulders is the harder hollow version.
No. They train the muscles, but exercising your abs doesn't remove the fat over them.
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. After a birth, start with the NHS's gentle tummy exercises and our diastasis recti guide's stages, and stop if the middle of your tummy domes.
The face-down version, lying on a bench with your legs off the end: it works your glutes and hamstrings, not your abs. Keep your legs at about level so your lower back doesn't arch.
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.
