Training guide
A V-up, or jackknife sit-up, starts lying flat with your arms overhead: you lift your straight arms and legs together until you balance for a moment in a V on your seat, then lower both slowly. It's a crunch and a leg raise at once, so it works your six-pack muscle and obliques hard and your hip flexors too, which is why it's a step up from crunches and reverse crunches.
It won't single out your lower abs, and nobody has tested V-ups on their own in a training trial, so this guide treats them as one good option among the hard ab moves, not a must.
It covers the move step by step on the 3D figure, the easier steps from the hollow hold and the tuck-up, how many to do, your lower back, neck and hip flexors, who should leave them out, and the warning signs.
Lie on your back with your legs long and your arms overhead. Breathe out and lift your straight arms and legs together, reaching your hands towards your shins, until you balance briefly on your seat in a V; then lower both slowly. The American Council on Exercise (ACE) rates its V-up intermediate.
Source 1
In 10 young men, the V-up worked the six-pack muscle and the obliques harder than tensing the tummy (abdominal bracing), at about 80% of the six-pack muscle's maximum as summarised in a review. Like any sit-up, it also works the deep hip flexors hard.
In most studies the upper and lower parts of the six-pack muscle worked alike, and a held V-up drew no more six-pack activity than a crunch. You can shift the emphasis a little; you can't isolate the lower part.
Dead bugs and the hollow hold, reverse crunches, the seated knee tuck and the tuck-up come first, then V-ups with your knees a little bent. ACE builds its V-up from seated, leaning-back leg lifts. Move up a step when your sets are smooth and your lower back stays under control.
Source 1
2 to 3 sets of 6 to 12, stopping 2 or 3 reps short, 2 or 3 days a week (our editorial starting point). Count V-ups with your other crunches and curls towards about 60 bending reps a session at most, as our sit-up guide suggests. Muscle grows from hard sets, so make them harder rather than doing more.
Source 8
With osteoporosis, in later pregnancy, in the first weeks after a birth, and with leaking, a prolapse, a hernia or recent tummy surgery, choose gentler core moves. If bending flares your back or sends pain down a leg, leave them out too.
From lying on your back with your arms overhead and your legs long, your straight arms and straight legs lift together until your hands reach towards your shins or feet and you balance for a moment on your seat in a V; then both ends lower slowly to the floor. Both levers are long, which is what makes it hard: your trunk curls and your hips bend at the same time.
V-up, V-sit-up and jackknife sit-up are one move. Close relatives: the tuck-up, or cocoon, bends your knees into your chest (the step before the V-up); the seated knee tuck on a bench is sometimes called a seated jackknife; the Swiss ball jackknife is a knee tuck in a plank on a ball; the V-sit hold, or boat pose, holds the V on your seat; the gymnastic V-sit is held on your hands (our L-sit guide); and the Pilates teaser rolls up slowly into a V.
The six-pack muscle (rectus abdominis), at about 80% of its maximum in 10 young men as summarised in a review; the outer obliques, which the V-sit and the reverse curl worked hardest of 5 common exercises in 25 adults; and the hip flexors, the deep psoas and the rectus femoris at the front of the thigh, which do much of the lifting in any sit-up. Your thighs hold your legs straight and together (our reading).
These studies used EMG (electromyography: electrodes measuring how hard a muscle works) over a few reps. That shows effort in one session; it isn't a validated predictor of what a muscle will build.
Source 15
Long legs make a longer, heavier lever; tight hamstrings stop your legs reaching high with straight knees, so bend them; and a larger chest, bust or belly makes the fold harder, so the tuck-up or seated knee tuck may suit you for longer (our suggestions).
The studies here are small groups of mostly young, healthy adults, and most measured one session in a lab. No trial has trained V-ups on their own. We say so where a point rests on them.
From our jackknife sit-up move page and ACE's V-up page; the breathing, neck and stopping cues are editorial, in line with our crunch and sit-up guides.
Loading the 3D figure…
The movement on the figure: Jackknife sit-up (V-up)
From our tuck-up (cocoon) move page, whose dose is 2 to 3 sets of 10 to 15 slow reps, stopping with 2 or 3 in reserve (our editorial starting point). If your lower back arches as you lie long, keep your arms by your sides and your feet just off the floor between reps, as the move page says.
Loading the 3D figure…
The movement on the figure: Tuck-up (cocoon)
In 10 healthy young men, the V-up (the study's V-sit: lying, arms overhead, legs lifted to 45 degrees with the arms reaching to the ankles) and the sit-up worked the six-pack muscle and the outer obliques significantly harder than abdominal bracing. A review of studies from 2012 to 2020 summarises the V-sit at about 80% of the six-pack muscle's maximum, among the highest of the exercises it covered.
In 21 adults holding six exercises still, a V-up drew six-pack and outer oblique activity no different from a crunch or V-ups on equipment, more inner oblique activity than a slide-board version, and more front-thigh activity than the crunch.
Source 5
In 25 healthy adults doing 5 common exercises, the V-sit and the reverse curl drew the most outer oblique activity.
Source 13
With fine-wire electrodes in 8 adults, every form of sit-up worked the deep psoas at 15 to 35% of its maximum, against under 10% in a curl-up; in students, the leg raise and a slow-lowering sit-up raised hip flexor activity. The V-up lifts your legs as well, so your hip flexors work hard (our reading).
A held V-sit and a front plank needed similar trunk effort, but the lower back was 28 degrees more rounded in the V-sit. As a test, a modified V-sit hold was less reliable than the prone bridge in 60 adults.
We found no training trial of V-ups on their own, and no measurement of the V-up's spine load or the pressure it puts on the pelvic floor. The training evidence for ab work in general is in our get abs and crunch guides.
In 20 students, the V-sit and the hanging leg raise drew more lower six-pack activity than 10 other exercises, and in 14 adults a Swiss ball jackknife (knees to chest in a plank on a ball, a different move) drew more lower than upper activity. But in 11 lean adults and in 8 adults, the upper and lower parts worked alike in every exercise, and in 25 adults the reverse curl, not the V-sit, drew the most lower six-pack activity.
On ultrasound in 15 students, the part of the muscle nearest the moving load changed most, but crunches thickened the whole muscle more than a leg raise did.
Source 20
The six-pack is one muscle: you can shift the emphasis a little, not isolate the lower part, as our leg raise and get abs guides conclude. Whether you can see it depends on the fat over it, and ab exercise doesn't burn that: 6 weeks of ab exercise changed no fat measure in 24 adults, and training one body part didn't reduce the fat over it across 13 studies.
In order, moving up when every set is smooth and your lower back stays under control: dead bug heel taps and dead bugs, 2 to 3 sets of 6 to 10 each side, and the hollow hold with your knees bent at first, 2 to 3 holds of 10 to 30 seconds (our 30-day ab challenge); reverse crunches, 2 to 3 sets of 8 to 15 (our 30-day ab challenge and lower ab workout); the seated knee tuck on a bench, the seated leg tuck and the tuck-up, each 2 to 3 sets of 10 to 15 slow reps, stopping with 2 or 3 in reserve (their move pages' editorial starting point); then V-ups, 2 to 3 sets of 6 to 12, stopping 2 or 3 reps short (our editorial starting point), knees a little bent at first. The held V on your seat (boat pose) is 3 holds of 3 to 5 breaths, knees bent and hands behind your thighs at first (our yoga for core workout). Harder: the Pilates teaser, 3 reps (its move page's dose); the hanging pike, 2 to 3 sets of 3 to 6 (our hanging leg raise progression); and the dragon flag, 3 or 4 sets of 3 to 5 slow lowers with the knees tucked first (our dragon flag progression). The alternating (one leg at a time) V-up and the V-up with a light weight or ball in your hands have no demo of their own.
3D demoDead bug heel tapsBeginner · No equipment
3D demoDead bugBeginner · No equipment
3D demoHollow body holdIntermediate · No equipment
3D demoReverse crunchIntermediate · No equipment
3D demoSeated knee tuck on a benchBeginner · A bench or box
3D demoSeated leg tuckBeginner · A bench or box
3D demoTuck-up (cocoon)Intermediate · No equipment
3D demoJackknife sit-up (V-up)Advanced · No equipment
3D demoBoat pose (Navasana)Intermediate · No equipment
3D demoTeaser (Pilates)Advanced · No equipment
3D demoHanging pikeAdvanced · Pull-up bar
3D demoDragon flagExpert · A bench or boxIn a model of 12 young men, bent-knee and straight-leg sit-ups both compressed the lower spine by more than 3,000 newtons; across 12 ab exercises in 9 volunteers, partial curl-ups gave the most ab work for the least spine load. Nobody has measured the V-up, but it bends your spine like a sit-up (our reading).
Our sit-up guide covers the debate about whether bending harms healthy backs and finds no study showing harm in sensible doses. The people who should change V-ups are those whose back pain flares with bending, and people with osteoporosis.
The authors of one study of 21 adults suggest that exercises with high front-thigh (rectus femoris) activity, such as pikes on a wheel and bent-knee sit-ups, "may be problematic for some people with low back problems". That is their view from muscle activity, not a trial; if V-ups bother your back, use dead bugs and bird dogs instead.
Source 25
Stop V-ups if they send pain, tingling or numbness down a leg, and use the dead bug or the McGill curl-up while it settles, as our sit-up guide says. Our back rule: discomfort up to about 5 out of 10 is acceptable if it settles within about an hour and is no worse the next morning.
Lift with your arms in line with your ears and your eyes on your knees; don't throw your head forward to get up (our cue, matching our crunch guide's "lift your chest, not your chin"). If your neck tires first, go back to the tuck-up or the hollow hold.
Cramping at the front of the hips means bending your knees or going back a step. Pain that lasts belongs to our hip flexor pain guide.
Swinging your arms and head to get up turns it into a fling; lead with your chest and arms, with your head in line, as the tuck-up page cues.
Lower with control rather than dropping your legs and back to the floor between reps, as the move page says.
Leading with your chin strains your neck. Keep your head between your arms (our cue).
Lifting your legs first and folding your trunk late makes it a leg raise with a sit-up tacked on: move both ends together (our cue).
Breathe out as you lift, as our breathing guide advises.
Doing them to failure or in hundreds adds bending without adding much. Make the move harder instead, as our sit-up guide says.
Tuck-ups, 2 to 3 sets of 10 to 15 slow reps, stopping with 2 or 3 in reserve: the move page's editorial starting point.
2 to 3 sets of 6 to 12, stopping 2 or 3 reps short, with 45 to 60 seconds between sets (our editorial starting point, matching our leg raise guide's 6 to 12 and the plans' effort note).
ACE builds the seated V from holds of 5 to 10 seconds to holds of 15 to 30 seconds.
Source 1
2 or 3 days a week, with a day between, as our get abs guide suggests.
About 60 bending reps a session in all, counting crunches, reverse crunches, tuck-ups and V-ups together. That's one expert review's suggestion, untested, as our sit-up guide labels it.
Add reps up to 12, then lower more slowly or pause in the V, then hold a light weight or ball (our suggestion, following the plans' progression note).
In 25 older adults, 100 bodyweight squats every day for 4 months improved no strength or muscle. Muscle grows from hard sets with light or heavy loads, about 10 or more a week, so harder versions do more than extra reps.
V-ups bend your spine; these work your trunk without bending it, or ease you in and out. Bird dogs, 1 to 2 sets of 6 each side with 3 to 5 second holds (our crunch and sit-up and lower ab workouts); side planks, or knee side planks, 2 holds of 15 to 30 seconds each side (our crunch and sit-up workout); forearm planks, 3 holds of 20 to 45 seconds (our plank guide, as our sit-up guide quotes it); glute bridges, 1 set of 10 to 12 (our lower ab workout); the half-kneeling hip flexor stretch, 30 seconds each side (our hanging leg raise progression); cat-cow, 8 slow waves, and child's pose, 1 to 3 minutes (their move pages' doses).
3D demoBird dogBeginner · No equipment
3D demoSide plankIntermediate · No equipment
3D demoKnee side plankBeginner · No equipment
3D demoForearm plankIntermediate · No equipment
3D demoGlute bridgeBeginner · No equipment
3D demoHalf-kneeling hip flexor stretchBeginner · No equipment
3D demoCat-cowBeginner · No equipment
3D demoChild's Pose (Balasana)Beginner · No equipmentThe V-up progression takes you from dead bugs and the hollow hold to the V-up; the lower ab, no-equipment ab and ab challenge workouts build the earlier steps; the crunch and sit-up workout keeps to about 60 bending reps; the dragon flag progression is the next hard lever.
A 20-minute ladder to the V-up: dead bugs and hollow holds, reverse crunches, seated knee tucks and tuck-ups, then V-ups, balanced with bird dogs and side planks.
20 minIntermediate11 movesA bench or boxA 15-minute lower ab workout: heel taps, reverse crunches and leg pull-ins, then lying leg raises and the hip lift. It trains your whole six-pack; pick your step.
15 minBeginner11 movesA bench or boxAn intermediate ab workout with no equipment: planks, side planks, reverse crunches, hollow holds and mountain climbers.
20 minIntermediate7 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 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 builds dead bugs, the hollow hold and reverse crunches, the steps before the tuck-up.
Leave V-ups out. The UK consensus advises modifying or avoiding repeated or end-range rounding of the spine, and spinal fractures have been reported with sit-ups. Train your trunk with dead bugs, bird dogs and planks instead.
Source 9
The NHS advises against lying flat on your back for more than a few minutes in later pregnancy, and against starting a new vigorous activity. Leave V-ups out in later pregnancy and use side-lying, all-fours or standing core work, as our pregnancy guide sets out.
Source 10
The NHS advises avoiding sit-ups to start with. In 70 women with a tummy gap 6 to 12 months after a birth, 12 weeks of head lifts and curl-ups didn't widen the gap and made the muscle thicker and stronger, but that trial used curl-ups, not V-ups. Build back through gentle tummy exercises, as our postpartum and diastasis recti guides set out, and choose an easier move if the middle of your tummy domes into a ridge as you curl.
The NHS says sit-ups can increase leaks, and in 57 women full sit-ups raised the pressure inside the tummy to a median of 60.4 cmH2O (centimetres of water, a pressure unit), against 18.5 for curl-ups. The V-up wasn't measured; our reading is that it sits with sit-ups. An NHS pelvic health leaflet advises people with a prolapse to avoid ab crunches. Use the pelvic floor guide's moves while you build up.
Leave V-ups 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.
Use the dead bug, bird dog and McGill curl-up instead, and see our back pain guide. Come back to tuck-ups first when it settles.
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.
Source 31
For chest pain that doesn't go away, feels tight, heavy or like squeezing, or spreads to your arms, neck, jaw, stomach or back, or comes with sweating, feeling sick, light-headedness or breathlessness; severe difficulty breathing; someone who faints while exercising; palpitations that don't go away, or come with chest pain, shortness of breath or feeling faint; or a headache that starts suddenly and is extremely painful, which the NHS says may be more likely when you're lifting something heavy. 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. Get advice before hard ab work if your blood pressure is uncontrolled, or you have heart disease, glaucoma, a hernia, recent eye or tummy surgery, or you're pregnant, as our breathing guide lists. With controlled high blood pressure, breathe out as you lift.
See a GP after any faint, and for dizziness that won't go away or keeps coming back.
If back pain comes with pain, tingling, weakness or numbness in both legs; loss of feeling around your genitals or bottom; new trouble peeing, or peeing or pooing yourself; or changes in how your penis or vagina feels during sex. These can be cauda equina syndrome, which needs treating in hospital urgently. Back pain with chest pain or after a serious accident, sciatica on both sides, and weakness or numbness in both legs that's severe or getting worse need the same.
Ask for an urgent GP appointment or contact NHS 111 for back pain with feeling hot, cold, shivery or unwell, or pain that is severe and sudden or getting worse quickly. See a GP if back pain isn't improving after a few weeks or is worse at night, or if neck pain or stiffness hasn't gone after a few weeks or comes with pins and needles.
A sudden sharp pain in your tummy wall during a set may be a strain: stop, and follow our abdominal strain guide. Get help from NHS 111 if it's very painful or swollen.
Source 44
See a GP if you think you have a hernia; get help from NHS 111 for pain in or around it. Call 999 or go to A&E for a femoral hernia (a small lump at the top of the thigh) with very bad tummy pain, being sick, or being unable to fart or poo.
A feeling of heaviness, discomfort or pressure in your lower tummy or vagina, or a bulge or lump, can be a prolapse: see a GP. Leaking is common and treatable: see a GP or pelvic health physiotherapist.
After a big or unusual session, such as a first "100 a day" challenge, severe muscle pain, swelling or weakness with dark urine needs same-day help: NHS 111, or A&E if you feel very unwell. Severe exertion, including calisthenics, is among the causes of muscle breakdown (rhabdomyolysis).
Source 48
One study found more lower six-pack activity in the V-sit than in most exercises; others found the upper and lower parts working alike, or a held V-up no different from a crunch, and the reverse curl, not the V-sit, worked the lower part most in 25 adults. You can shift the emphasis a little; you can't isolate the lower abs.
6 weeks of ab exercise changed no fat measure in 24 adults, and training one body part didn't reduce the fat over it across 13 studies of 1,158 people. Fat comes off your whole body, with your overall activity and eating.
Sit-ups compress the lower spine by more than 3,000 newtons and nobody has measured the V-up, but our sit-up guide finds no study showing harm to healthy backs in sensible doses. People whose back pain flares with bending, and people with osteoporosis, should leave them out.
Every sit-up worked the deep psoas at 15 to 35% of its maximum, against under 10% in a curl-up, and the V-up lifts your legs too. Cramping at the front of the hips means bending your knees or going back a step.
Source 4
Bend your knees as much as your hamstrings need, as the move page cues, or use the tuck-up: your abs still do the curling.
In 25 older adults, 100 bodyweight squats every day for 4 months built no strength or muscle; muscle grows from hard sets, about 10 or more a week. Keep to about 60 bending reps a session and make the move harder instead.
Muscle activity in one session isn't a validated predictor of growth, which is why this guide calls it effort, not results.
Source 15
Lie on your back with your legs long and your arms overhead. Breathe out and lift your straight arms and legs together, reaching your hands towards your shins, until you balance briefly on your seat in a V. Lower both slowly, without thumping down, and go again.
Mainly the six-pack muscle and the obliques, which worked about as hard as in any floor exercise measured, plus the hip flexors, which lift your legs and help lift your trunk. Your thighs hold your legs straight.
Not on their own. One small study found more lower six-pack activity in the V-sit, but others found the upper and lower parts working together. The six-pack is one muscle, and seeing it depends on the fat over it, which ab exercises don't burn.
It moves both long levers at once, so it needs strong abs, strong hip flexors and enough hamstring range. Build up with the hollow hold, reverse crunches, the seated knee tuck and the tuck-up, and bend your knees a little at first.
Start with 2 to 3 sets of 6 to 12, stopping 2 or 3 reps short, 2 or 3 days a week, as our editorial starting point. Count them with your other crunches and curls towards about 60 bending reps a session, one expert review's untested ceiling.
You don't need to. Two or three ab sessions a week is plenty, and big daily rep counts add bending without adding much. Make the move harder instead.
Not for most healthy backs in sensible doses, but they bend your spine like a sit-up, which compressed the lower spine by more than 3,000 newtons in a lab model. If bending flares your back or sends pain down a leg, swap to dead bugs and bird dogs and see our back pain guide.
Often your lower back is arching as your legs lift or drop, or you're swinging up. Lower slowly, bend your knees, or go back to tuck-ups or the hollow hold. Pain that spreads down a leg, or doesn't settle within about an hour, is a reason to stop.
Harder, not better. A held V-up drew about the same six-pack activity as a crunch in one study, with more hip flexor work. Use crunches to build up, then V-ups if you want an advanced curl.
A V-up and a jackknife sit-up are the same move. A tuck-up bends your knees into your chest, a shorter lever and the step before. A V-sit hold is a held V on your seat, like the boat pose.
Leave them out in later pregnancy, when the NHS advises against lying flat on your back for more than a few minutes, and use side-lying, all-fours or standing core work. After a birth, the NHS advises avoiding sit-ups to start with; build back through gentle tummy exercises, as our postpartum and diastasis recti guides set out.
No. The UK consensus advises modifying or avoiding repeated or end-range rounding of the spine, and fractures have been reported with sit-ups. Train your trunk with dead bugs, bird dogs and planks instead.
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.
