Training guide
A clamshell is a side-lying exercise for the side and back of your hip. Lie on your side with your hips and knees bent and your feet together, then open your top knee towards the ceiling without letting your pelvis roll back, and lower it slowly. It works the gluteus medius, the upper part of the gluteus maximus and the small rotators deep in the hip, with little help from the muscle at the front of the hip.
It's a gentle exercise: in most studies the gluteus medius worked harder in side-lying leg raises, single-leg bridges and standing band work, so clamshells are a starting point you'll outgrow. They help kneecap pain as part of hip and knee strengthening, though the evidence for them on their own is mixed, and with pain on the outside of the hip they come later, lying on your good side with a pillow between your knees.
This guide shows you the technique step by step on the 3D figure, bands, what the studies measured, knee and outer hip pain, the versions, how many, and the warning signs.
Lie on your side, hips and knees bent and feet together, and open your top knee towards the ceiling only as far as your pelvis stays still. An NHS physiotherapy leaflet puts it plainly: don't let your hips roll backwards, and you should feel it working over your bottom.
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Clamshells work the gluteus medius (its back part most), the upper gluteus maximus and the deep hip rotators, and they use the muscle at the front of the hip less than most hip exercises do.
Across 10 studies, the middle of the gluteus medius worked at about 17 to 28% of its maximum in clamshells, and side-lying leg raises drew about twice the activity of clamshells in 21 people. Clamshells are a starting point: you'll move on to harder side-hip work.
Adding hip strengthening to knee exercises eased kneecap pain more than knee exercises alone (14 trials, 673 people). But in a trial of 112 people whose hip programme included clamshells, hip exercise did no better than knee exercise or free activity.
The trial that did best for outer hip tendon pain didn't use clamshells. While the outside of your hip hurts, especially at night, leave them out and start with our outer hip pain guide's holds and bridges; when they come back, lie on your good side with a pillow between your knees.
2 or 3 sets of 12 to 15 each side, 2 or 3 times a week (our beginner lower body workout and runner's knee guide), stopping 1 or 2 reps short; an NHS trust leaflet uses 3 sets of 8 to 12. Add a light band when 3 sets of 15 feel easy (our suggestion).
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Lying on your side with your hips and knees bent and your feet together, you open the top knee towards the ceiling and close it slowly, keeping your pelvis still. It turns the top thigh outwards and lifts it a little to the side, from a bent-hip position.
The gluteus medius, its back part more than its middle or front; the upper part of the gluteus maximus; and the deep hip rotators, the piriformis and obturator internus. The muscle at the front of the hip (the tensor fasciae latae) works relatively little, which is why rehabilitation programmes like it. Rolling your pelvis back cuts the glutes' share, and a weight on the thigh brought in the hip flexors in one study.
Most studies used EMG (electromyography: electrodes measuring how hard a muscle works over a few reps), some with fine wires in the deep muscles, and one used MRI (magnetic resonance imaging) scans after the exercise. These show effort, not what a muscle will build.
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Being comfortable lying on your side, with the bottom hip padded if it's sore, as the clamshell's move page says.
From the clamshell's move page and an NHS physiotherapy leaflet (South Tees), with the hip and knee angles from studies that found more glute work with the hips bent to about 60 degrees and the knees to 90. The one-second hold is our editorial suggestion. Sore on the outside of your hip? Read "Clamshells and outer hip pain" first.
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The movement on the figure: Clamshell
Across 56 studies, clamshells drew low to moderate gluteus medius activity: about 17 to 28% of maximum for its middle part in 10 studies. Hip hitches, single-leg bridges, side-lying leg raises with the hip turned in, lateral step-ups, standing band work and resisted side steps did better. In 21 people, side-lying leg raises drew 81% against 38 to 40% in two clamshell versions.
With fine-wire electrodes in 20 healthy people, the clam had the highest ratio of glute to front-of-hip muscle activity of the exercises tested. In 11 people, clams with and without a band topped that ratio among 13 exercises, and in 12 people with kneecap pain the banded clam was the only one of 11 exercises that worked both glute muscles significantly more than the front-of-hip muscle.
In 10 adults scanned after 40 reps, clamshells changed the gluteus medius by 4.5%, against 11.6% for single-leg bridges and 13.2% for side-lying leg raises with the leg turned out, but changed the deep rotators more than reverse clams did: the piriformis by 14.5% and the obturator internus by 24.2%.
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With fine wires in 10 young adults, the side-lying clam didn't recruit the front and middle parts of the gluteus medius well, and in 10 postmenopausal women clamshells ranked low while the hip hitch ranked highest for the gluteus medius and minimus.
In 11 men doing 10 maximal reps, the gluteus medius worked the same in clamshells, side-lying leg raises and the hip abduction machine, and a hard clamshell progression reached 77% of maximum in 24 people. How hard you push, and how you load it, changes the numbers.
Activity over a few reps isn't a validated predictor of growth, so these studies tell you what clamshells work, not what they build. The glutes section below covers the training trials.
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In 17 people, an upright pelvis drew more gluteus maximus and medius activity than a pelvis rolled back, and the gluteus medius worked hardest with the hips bent to 60 degrees. Rolling back turns it into a different, easier exercise, as the move page says.
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In 30 women, the upper gluteus maximus worked more with the hips bent to 45 or 60 degrees than to 30, and a second study from the same group found the same for the back of the gluteus medius. The move page's 45 degrees is fine to start, and a little more bend works well (our reading).
In 30 women, a modified clamshell with the knees bent to 90 or 110 degrees drew more gluteus medius activity, and less from the front of the hip and the side of the trunk, than at 60 degrees. Activity was low throughout, which the authors read as training control rather than strength.
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In women whose thigh bones were more inwardly twisted (femoral anteversion), clamshells worked the front-of-hip muscle more relative to the glutes. If you feel it mostly at the front of your hip, check your pelvis is stacked and bend your hips a little more.
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Without a band, clamshells still work the gluteus medius and the deep rotators. Start without, and add a light mini band just above your knees when 3 sets of 15 feel easy (our editorial suggestion).
A hard clamshell progression reached 77% of maximum gluteus medius activity in 24 people, and in 12 people with kneecap pain the banded clam was the only one of 11 exercises that worked both glute muscles more than the front of the hip.
In 20 distance runners with a load of 5% of body weight on the thigh, the hip flexors worked harder (54%) than the gluteus medius (33%) in clamshells. A band is the better way to make it harder (our reading).
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In one knee pain trial, clamshells went from 3 sets of 10 to 3 sets of 20 before resistance was added.
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It's usually too narrow or too low on the thigh: move it just above your knees or use a wider band (our suggestion).
In 14 trials of 673 people with kneecap pain (patellofemoral pain), adding hip strengthening to knee exercises cut pain by about 1.5 points more on a 0 to 10 scale and improved activity more; strength itself didn't change significantly.
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In 33 women with kneecap pain, 4 weeks of hip strengthening before functional exercise left less pain than starting with thigh (quadriceps) strengthening.
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In 112 people aged 16 to 40 with kneecap pain, 6 weeks of hip exercise (side-lying leg raises, clamshells and lying hip extension, 3 sets of 10 building to 3 sets of 20), knee exercise or free physical activity, each with the same education, gave no differences at 3 months or a year. So clamshells belong in hip and knee strengthening, but they aren't a fix on their own.
In 40 people 1 to 3 years after anterior cruciate ligament reconstruction, adding clamshells to usual exercises improved pain, function and the knee's ability to straighten fully more than usual exercises alone. It's one small trial.
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Our runner's knee and front of knee pain guides use clamshells, 3 sets of 12 to 15. Knee pain of 0 to 2 out of 10 during and after is fine, and up to 5 is acceptable if it's back to its usual level by the next morning, as our knee guides say.
In the LEAP trial of 204 people with outer hip tendon pain (gluteal tendinopathy), education plus exercise beat a steroid injection and waiting to see at 8 weeks (51 of 66 improved, against 38 of 65 and 20 of 68). Its programme started with lying and standing holds, bridges, small squats and side steps, avoided crossing the leg over and stretching, and used no clamshells.
Clamshells start lying on your side with your hips bent and your knees together, close to the squeezing position that outer hip tendon education teaches you to avoid (our reasoning from the LEAP trial's programme). Our hip pain at night guide says the same: the lying hold now, side-lying work later.
To work a sore hip, you lie on your good side, because it's the top leg that works; to work the other leg you'd lie on the sore hip, so pad it well or leave that side out for now. NHS inform advises avoiding sleeping on the painful side.
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Lie on your good side with a pillow between your knees, so your top thigh stays level with your hip rather than dropping across your body, as NHS inform suggests for sleeping and for its side-lying exercise; when the LEAP trial measured hip strength lying on the side, it rested the top leg on pillows to avoid squeezing the tendon. Keep the range small, use no band or a light one, and don't let your pelvis roll back.
No extra pain over the bony point on the side of your hip during or after, and the hip no worse that night or the next morning, as our outer hip pain guide says. NHS inform keeps pain at 0 to 5 out of 10 and no worse the next morning, and stops any exercise that makes symptoms worse or causes new pain. Heavy bands can wait.
In 17 adults training each leg differently for 10 weeks, loaded cable hip abduction grew the gluteus medius and minimus by 4% and the upper gluteus maximus by 10%, while hip extension grew the gluteus maximus more. In 34 adults, hip thrusts and squats grew the glutes alike over 9 weeks but the gluteus medius and minimus little. Clamshells are lighter than either; the main glute muscle grows from loaded hip extension, as our glute guide explains.
Hip dips are a normal part of many people's shape. Training one area doesn't burn the fat over it: across 13 studies of 1,158 people, training one limb didn't reduce the fat on that limb. Side-hip work can build the muscle there a little, but no plan can promise a shape.
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Hip strengthening added small, uncertain benefits for low back pain in a review, and we found no trial of clamshells for sciatica, piriformis pain or sacroiliac joint pain. Physiotherapists often include them, but that's practice, not proof.
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Lying belt-press holds, 3 to 5 holds of 5 to 10 seconds twice a day at a light effort, and standing wall-press holds, 3 to 5 holds of 5 to 15 seconds each side twice a day (their move pages' doses, from the LEAP programme); glute bridges, 2 to 3 sets of 10 to 15 (our beginner lower body workout); clamshells, 2 or 3 sets of 12 to 15 each side (our beginner lower body workout and runner's knee guide), with a light band once 3 sets of 15 are easy; side-lying leg raises, 12 each side (our glute workout at home); side planks with a leg lift, 2 sets of 8 to 10 each side (our strength workout for runners at home); and standing band hip abduction, 1 to 2 sets of 12 to 15 each side (our glute challenge workout B).
3D demoSupine isometric hip abduction (belt press)Beginner · A band
3D demoStanding wall-press hip abductionBeginner · A wall
3D demoGlute bridgeBeginner · No equipment
3D demoClamshellBeginner · No equipment
3D demoSide-lying leg raiseBeginner · No equipment
3D demoSide plank with leg liftAdvanced · No equipment
3D demoStanding band hip abductionBeginner · A band + An anchor pointThe same position, but you lift your top foot while your knees stay together, turning the thigh inwards. It worked the deep rotators less than the clamshell on MRI; it's a gentle add-on, not a replacement.
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The knee side plank with the top knee opening: a much harder version, since side planks with a leg lift drew some of the highest gluteus medius activity in studies. Start from the knee side plank.
A band round your thighs, standing in a quarter squat and turning one knee out. Our figure doesn't show it.
Opening the knees against a band, sitting or lying on your back. The lying belt-press hold is the demonstrated lying version, and the one our outer hip pain guide starts with.
Lateral band walks, 10 steps each way (our glute gym workout); monster walks, 2 to 3 sets of 10 to 15 steps forward and the same back (its move page's dose); single-leg glute bridges, 3 sets of 10 to 15 each side (our lower body workout at home); the staggered-stance bridge, 5 slow reps each side once a day, building to 2 sets of 5 to 10 (its move page's dose, from the LEAP programme); the hip abduction machine, 3 sets of 12 to 20 (our glute gym workout); and the knee side plank, where the side plank clamshell starts. The hip hitch, among the hardest gluteus medius exercises in the studies above, has a move page without a 3D demo.
3D demoLateral band walkBeginner · A band
3D demoMonster walkBeginner · A band
3D demoSingle-leg glute bridgeIntermediate · No equipment
3D demoStaggered-stance bridge (offset bridge)Beginner · No equipment
3D demoHip abduction machineBeginner · Strength machine
3D demoKnee side plankBeginner · No equipmentRest a hand on your hip and open less: rolling back turns it into a different, easier exercise, as the move page says.
Keep them touching the whole time.
Check your pelvis is stacked, bend your hips a little more, and take any weight off your thigh.
Slow up, a second at the top, slow down.
Pad it, or leave that side out for now.
Use a lighter band and open only as far as your pelvis allows.
Keep your ribs down and your back long.
2 or 3 sets of 12 to 15 each side, stopping 1 or 2 reps short; the last set can go closer to failure, as our plans allow for small exercises like this (our beginner lower body workout and runner's knee guide). An NHS trust leaflet for kneecap pain uses 3 sets of 8 to 12, and one trial built from 3 sets of 10 to 3 sets of 20, three times a week.
60 to 90 seconds, or less if you alternate sides, since each side rests while the other works (our plans; our beginner lower body workout rests 45 seconds).
2 or 3 times a week for strength. Light daily sets are fine in a rehabilitation plan; NHS inform spreads its outer hip exercises through the day.
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Reps to the top of the range, then a light band, then a stronger band or a harder exercise from the steps above (double progression, as our plans use).
Once 3 sets of 15 with a band are easy, move on to side-lying leg raises, side planks with a leg lift, standing band work and single-leg bridges, which worked the gluteus medius harder in studies.
Our beginner lower body and glute at home workouts use clamshells as a starter; the hip release routine and Pilates glute workout pad the bottom hip or skip them with a sore outer hip; the pregnancy strength workout and postnatal exercises use pillows; and the glute challenge and lateral pelvic tilt routines take you beyond them.
Learn to squat, hinge and lunge: a 25-minute beginner lower body workout with bridges, clamshells and calf raises.
25 minBeginner11 movesA wall, A bench or boxA 25-minute glute workout with bodyweight and a mini band: bridges, clamshells, band walks, kickbacks and lunges.
25 minBeginner9 movesA wall, A bandStiff hips and glutes: a few minutes of rolling the glutes and thighs, two stretches while the extra range lasts, then strength work to keep it. About 15 minutes.
15 minBeginner7 movesA foam rollerA 25-minute Pilates class for your glutes: bridges, the side kick series, face-down kicks and standing work at a wall, with a band to make it harder.
25 minBeginner16 movesA wall, A bandA 30-minute strength workout for any trimester with dumbbells and a band: squats, rows, hinges, presses and side-lying hip work, none on your back.
30 minBeginner14 movesA dumbbell, A bench or boxA gentle 25-minute routine for the first weeks after birth: pelvic floor, breathing, tummy and hip exercises on the floor, sit-to-stands and a walk.
25 minBeginner12 movesA bench or box, Cardio machineSession A of the 30-day glute challenge: a bridge-to-hip-thrust ladder, a split squat ladder and side-hip work, at home or in the gym.
20 minBeginner16 movesA wall, A bandA 25-minute routine for uneven hips: side-hip holds, leg raises, single-leg bridges, step-ups, side planks and balance, for hip strength and pelvic control.
25 minBeginner10 movesA wall, A stepThese plans use our glute workout at home, glute challenge workout A or beginner lower body workout, all of which include clamshells.
An 8-week glute workout plan: two glute days and two upper-body days a week, with hip thrusts, squats, hinges and side-hip work, plus a home option.
4 training days50 minIntermediate3 days a weekA free 30-day glute challenge for home or the gym: three 20-minute sessions a week with bridges, split squats, hinges and side-hip work, and rest days.
3 training days20 minBeginner3 days a weekA 9-week beginner plan with the same walk-to-run shape as Couch to 5K: three run-walk sessions a week, from 1-minute jogs to 30 minutes of running.
3 training days35 minBeginnerClamshells are usually fine with pillows under your head and bump and between your knees, as our pregnancy strength workout uses them. With pelvic girdle pain, keep the range small: the NHS says moving your legs apart can make it worse, and a pillow between your legs in bed can help.
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Our postnatal exercises use clamshells with a pillow between the knees. No study has tested clamshells for the pelvic floor; our pelvic floor guide covers the exercises that do help.
Call your midwife or GP if you have pelvic pain and it's hard for you to move around, it hurts to get out of a car or turn over in bed, or it's painful going up or down stairs.
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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 comes on suddenly and doesn't go away, feels tight or like squeezing, or spreads to your arms, neck or jaw; someone who faints while exercising; palpitations that don't go away, or come with chest pain, breathlessness or feeling faint; or signs of a stroke, even if they've stopped. Don't drive yourself to A&E.
Call 999 or go to A&E for severe hip pain after a fall or injury, if you can't walk or put weight on your leg, or for tingling or loss of feeling in your hip or leg after an injury. Ask for an urgent GP appointment or get help from NHS 111 for severe hip pain that started suddenly without a fall, a hip that's swollen and feels hot, skin around it that has changed colour, or hip pain with feeling generally unwell and a high temperature.
See a GP if hip pain stops you doing normal activities or affects your sleep, is getting worse or keeps coming back, hasn't improved after 2 weeks of treating it at home, or you have hip stiffness for more than 30 minutes after waking up.
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Outer hip pain that hasn't improved within 6 weeks of following our outer hip pain guide's advice, or that gets worse: talk to a GP or physiotherapist. In many areas you can refer yourself.
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Get advice from NHS 111 if your knee is very painful, you can't move it or put weight on it, it's badly swollen or has changed shape, or it locks, gives way or clicks painfully; painless clicking is normal. In the US, use urgent care.
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Pain, tingling or numbness spreading below the knee that isn't settling after a few weeks, is getting worse or stops your normal activities: see a GP, as our outer hip pain guide says.
Muscle soreness for a day or two after a new or harder session is common and fades. Sharp pain, or pain that builds during a set or lingers into the next day, isn't: swap to an easier version, and see a clinician if it persists, as our plans advise. The NHS says to stop exercising straight away if you feel any pain or become unwell, and to get help from 111 if symptoms worry you or don't go away.
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They work the side of the hip lightly but with little help from the front of the hip, which makes them a good early exercise, and they belong in hip work for kneecap pain, where hip and knee strengthening together beat knee work alone. You outgrow them, as the move page says.
Without a band they still work the gluteus medius and the deep rotators. A band makes them harder, and in people with kneecap pain the banded clam was the only one of 11 exercises that worked both glute muscles more than the front of the hip.
Hip strengthening helps as part of a hip and knee programme, but in one trial whose hip programme included clamshells, hip work was no better than knee work or free activity with education.
No trial has tested them for it. The trial that worked best for outer hip pain didn't use them: it started with holds, bridges, small squats and side steps and avoided squeezing positions. Clamshells can come in later, lying on your good side with a pillow between your knees.
Hip dips are a normal part of many people's shape. Side-hip training can build the muscle there a little, but training one area doesn't burn the fat over it, and no plan can promise a shape, as our glute guide says.
The side glutes grew a little with loaded hip abduction training; the main glute muscle grows from loaded hip extension, as our glute guide explains.
Activity over a few reps isn't a validated predictor of growth. Clamshells drew little gluteus medius activity in most studies yet worked the deep rotators hard on MRI; training trials, not activity, decide what builds muscle.
The side and back of your hip: the gluteus medius, the upper part of the gluteus maximus and the deep hip rotators. They use the muscle at the front of the hip relatively little, which is why physiotherapists like them early in rehabilitation.
No. Start without, and add a light band just above your knees when 3 sets of 15 feel easy. A band makes it harder, and in people with kneecap pain the banded clam was the only one of 11 exercises that worked both glute muscles more than the front of the hip.
2 or 3 sets of 12 to 15 each side, 2 or 3 times a week, stopping 1 or 2 reps short; an NHS leaflet uses 3 sets of 8 to 12. Light daily sets are fine in a rehabilitation plan.
You should feel them at the side and back of your hip. Feeling them at the front of your hip often means a weight has brought in your hip flexors, or your pelvis has rolled back, which cut the glutes' share in a study. Pain over the bony point on the side of your hip, or in your knee, is a reason to stop and read our outer hip or knee guides.
As part of hip and knee strengthening, yes: adding hip work to knee exercises eased kneecap pain more than knee exercises alone. On their own they aren't a fix: in one trial, hip work including clamshells was no better than knee work or free activity with education.
Not as a first step. The trial that worked best for outer hip tendon pain used holds, bridges, small squats and side steps, not clamshells. Never lie on the sore side, and when you add side-lying work back, lie on your good side with a pillow between your knees, keeping the bony point no sorer that night.
They strengthen the side of your hip, but they're too light to build much muscle; the main glute muscle grows from loaded hip extension. Hip dips are a normal shape, no exercise spot-reduces fat, and no plan can promise a shape.
Side-lying leg raises worked the gluteus medius about twice as hard as clamshells in one study, though another found all three alike. Clamshells are the gentle start, and the machine is the easiest to load in small steps, as our hip abduction machine guide explains.
Physiotherapists often include them, but no trial has tested clamshells for these, and hip strengthening added only small, uncertain benefits for back pain in a review. Follow our sciatica, piriformis and back pain guides for those.
Usually, yes, with pillows under your head and bump and between your knees. With pelvic girdle pain, keep the range small, since moving your legs apart can make it worse.
The same position, but you lift your top foot while your knees stay together, turning the thigh inwards. It worked the deep hip rotators less than a clamshell in a scanning study; it's a gentle add-on, not a replacement.
No study has tested clamshells for the pelvic floor. Pelvic floor muscle exercises are the tested approach: see our pelvic floor guide.
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.
