Lying leg raise
Also called leg raises, lying leg raises, floor leg raise, supine leg raise.
What is a lying leg raise?
A lying leg raise is a bodyweight core exercise: lie face up, lift both straight legs until they point roughly up over your hips, then lower them under control without letting your lower back come off the floor. The legs are moved by the hip flexors, the iliopsoas above all, while the rectus abdominis and the rest of the abdominal wall work isometrically, holding the pelvis and keeping the lower back on the floor. That isometric hold is what the exercise is done for.
How do you perform a lying leg raise?
Set up
- Lie face up with your legs straight and together, and place your hands palms down beside your hips.
- Press your lower back into the floor and lift your heels just off it.
Execution
- Raise both legs together until they point roughly up over your hips, keeping your knees straight or at the same small bend.
- Lower your legs together and under control.
- Stop as soon as your lower back starts to lift, then begin the next rep without bouncing your heels off the floor.
Common mistakes
Letting the lower back arch off the floor
The psoas major attaches to the lumbar vertebrae themselves, so when the abdominal wall can no longer hold the pelvis the hip flexors get a direct pull on the lumbar spine and it arches. At that point the abs have stopped doing the work the exercise exists for, and the lower back is holding a long lever on its own.
Bouncing the heels off the floor to start each rep
The hardest part of a leg raise is the legs just off the floor, where the lever is longest and the pelvis is closest to being pulled out of position. Momentum carries you through exactly that part. It also hides the arch, because a fast rep is finished before you notice the back lift.
Treating it as an abdominal contraction
Nothing in the visible movement is done by the abs, so if you wait to feel them shorten you will simply swing your legs. Their work here is isometric and it shows up as the effort of keeping the back flat, not as a crunching sensation. A set that leaves only the hip flexors tired never asked the abdominal wall for its half.
Letting the knees bend a little more with every rep
A bent knee shortens the lever and makes the movement substantially easier, which is a fine way to scale it but not something that should creep in unnoticed mid-set. Pick the knee angle before the set and hold it, so that the reps you count are the same exercise.
Where it fits in a session
Core work at the end of a session. In the logs it most often lands at the end of a lower-body day.
Bodyweight and awkward to load, so progress it by range and tempo before weight: get the heels lower with the back still flat, then slow the descent, then add ankle weights — or a dumbbell squeezed between the feet, if you trust the squeeze, since it is above your face for the whole set. Two or three sets of eight to fifteen reps, counting only the reps where the back stayed down.
Muscles worked
- iliopsoas (iliacus and psoas major)
- rectus abdominis
- rectus femoris
- sartorius
- pectineus
- external oblique
- internal oblique
- transversus abdominis
Two jobs, not one ranking. The legs are raised by the hip flexors, and the iliopsoas is the primary flexor of the thigh at the hip, with rectus femoris, sartorius and pectineus assisting. The rectus abdominis runs from the pubis to the lower ribs and does not cross the hip at all, so it cannot lift a leg: it is a flexor of the vertebral column, and here it works isometrically, holding the pelvis and keeping the lower back down while the hip flexors pull. The obliques and transversus abdominis work with it, bracing rather than moving. It is listed alongside the iliopsoas because that isometric job is what the exercise is done for, not because the anatomy ranks one above the other. Which of the two does more work in a given rep is an activation question the anatomy references do not answer, so this page does not answer it either.
What lifters actually do
About a third of regular RepCount users have logged a lying leg raise at some point, and it appears in roughly one workout in thirty — tried widely, used sparingly. Where it appears is more revealing than how often. Apart from crunches, every movement that commonly shares a session with it is lower-body work: leg extensions, squats, leg curls and the leg press. Leg raises are not usually part of a dedicated core session. They are added to the end of a leg day, about three sets of them, in workouts that run slightly longer than average.
Most often trained alongside
Share of lying leg raise sessions that also include each exercise.
- Crunches20.8%
- Leg extension19.6%
- Squat15.7%
- Leg curl15.3%
- Leg press12.9%
Figures come from workouts tracked in RepCount.
Variations
- Lying knee raise — Knees bent to shorten the lever. The usual scaling step when the lower back will not stay flat.
- Single leg raise — One leg at a time, roughly halving the load on the pelvis.
- Flat bench leg raise — Holding the bench above your head, so the legs can travel below the level of your hips.
- Decline bench leg raise — Head at the high end of the bench, which lengthens the range at the bottom.
- Hanging leg raise — The same hip flexion from a bar, with no floor to brace the pelvis against.
- Captain's chair leg raise — Forearms on the pads and back supported, which removes the grip demand of hanging.
- Reverse crunch — Hips curl off the floor at the top, adding spinal flexion to the hip flexion.
- Weighted leg raise — A dumbbell or medicine ball squeezed between the feet, or ankle weights.
Frequently asked questions
What muscles do lying leg raises work?
The hip flexors move your legs and the abdominal wall holds your pelvis still while they do. The iliopsoas — the iliacus and psoas major, which share a tendon onto the femur — is the primary flexor of the thigh at the hip, and rectus femoris, sartorius and pectineus flex the hip alongside it. The rectus abdominis, the obliques and transversus abdominis work isometrically: the rectus abdominis runs from the pubis up to the fifth through seventh costal cartilages, so it flexes the spine and cannot act on the hip at all.
Do leg raises work the lower abs?
They load the abdominal wall hard, but not in the way the phrase suggests. The rectus abdominis is one muscle on each side running from the pubis to the lower ribs, divided into four segments by three tendinous intersections. Whether one end of it can be trained preferentially is a question about muscle activation, and this page makes no claim either way. What the anatomy does settle is that the rectus abdominis does not cross the hip, so it is not what lifts your legs. Its job on a leg raise is to stop your pelvis being pulled into a tilt, which is a demand most crunch variations never make of it.
Why does my lower back come off the floor during leg raises?
Because the demand on your abdominal wall is highest when your legs are lowest, and because the psoas major attaches to the lumbar vertebrae themselves. Once the abs can no longer hold the pelvis, the hip flexors have a direct pull on the lumbar spine and it arches. Do not push through it: stop the descent higher, bend the knees, or drop to one leg at a time, until the flat back lasts the whole set.
Should I do leg raises on the floor or on a bench?
Either. This is a preference, not a technique point, and the illustration on this page can only show one of them. The floor is the more common choice and it gives you an immediate signal, because you feel the moment your back lifts. A flat or decline bench lets you hold on above your head and take the legs below the level of your hips, which adds range at the hard end. Where you put your hands is a preference too: beside your hips, or tucked under your glutes, which tips the pelvis slightly and makes a flat back easier to hold.
Are leg raises better than crunches?
They are not the same job. A crunch flexes the spine, bringing the ribs toward the pelvis. A leg raise asks the abdominal wall to resist the pelvis being pulled while the spine barely moves, and it does that with the hip flexors loaded at the same time. Neither replaces the other, and lifters do not seem to treat them as alternatives: crunches are the single movement that turns up most often in the same session as a leg raise.
Should my legs be completely straight?
Straighter legs mean a longer lever and a harder exercise, so straight is the harder version rather than the correct one. A small fixed bend is fine, and it is the sensible choice if hamstring length is what stops you rather than your midsection. What matters is that the angle does not change during the set: knees that bend a bit more with each rep quietly turn the exercise into a knee raise.
How many sets of leg raises should I do?
In RepCount, a workout containing leg raises has just under three sets of them on average, which is a reasonable place to start. The more useful number is how many reps you complete with your lower back still on the floor, because that is the only part of the set the abdominal wall is actually working. When that number stops moving, add range or slow the descent before you add sets.
Are lying leg raises worth doing?
About a third of regular RepCount users have logged them at some point, and they show up in roughly one workout in thirty. The company they keep is the interesting part: apart from crunches, the movements that most often share a session with them are leg extensions, squats, leg curls and the leg press. That is a lower-body day, not an ab session. Treated that way — a few sets of honest reps at the end of leg training — they load the abdominal wall in a position nothing else in that session does.
Sources
- Anatomy, Bony Pelvis and Lower Limb: Iliopsoas Muscle. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK531508/
- Anatomy, Abdomen and Pelvis: Abdominal Wall. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK551649/
- Anatomy, Abdomen and Pelvis, Rectus Sheath. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK537153/
- Anatomy, Bony Pelvis and Lower Limb: Anterior Thigh Muscles. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK538425/
- Anatomy, Abdomen and Pelvis, Rectus Femoris Muscle. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK539897/