Lying Leg Raise
What Is the Lying Leg Raise?
Lying Leg Raise is an isolation exercise that primarily targets the core, working the hip flexors and abdominal muscles together. It is a beginner-level movement that requires no equipment and can be performed on a mat or flat surface, making it highly accessible for those looking to strengthen their core.
This exercise is often included in abdominal workouts and is commonly described as a lower-ab exercise, but the legs are actually lifted by the hip flexors, mainly the iliopsoas and the rectus femoris. In a study of 20 healthy young adults, the lying straight-leg raise produced more hip flexor activity and less upper-ab and oblique activity than a bent-knee sit-up. The abdominals have a different job: as the hip flexors pull on the pelvis, the abs hold it steady so the lower back does not arch off the floor. That demand is highest when the straight legs are low and close to the floor, where their leverage is greatest, and it eases as they approach vertical.
Unlike crunches, which curl the rib cage toward a fixed pelvis and tend to emphasize the upper portion of the rectus abdominis, the lying leg raise keeps the pelvis still, so the abs work mainly to stabilize rather than to curl. The upper-versus-lower difference is modest either way, since the rectus abdominis is one continuous muscle and the whole muscle works in both. To shift more of the work toward its lower portion, the Reverse Crunch curls the pelvis up toward the rib cage, while the Lying Knee Raise bends the knees to shorten the lever and is an easier starting point.
Additionally, the lying leg raise helps improve core stability by training the abdominals to keep the pelvis and lower back still while the legs move. That same demand makes it a poor fit for some people: if the lower back arches as the legs lower, or back pain flares when it does, bending the knees or lowering the legs only as far as the lower back stays flat keeps the load manageable. Performing it with proper form and control enhances muscle activation while minimizing strain on the lower back.
Muscles Worked
- Rectus Abdominis (Lower)
- Primary
- Rectus Abdominis
- High
- Rectus Femoris
- High
- External Oblique
- Medium
- Sartorius
- Minimal
Instructions
- Lie flat on your back with your legs extended and your arms at your sides, palms down, for support.
- Engage your core and press your lower back into the floor.
- Keeping your legs straight, slowly lift them upward until they point toward the ceiling at about a 90-degree angle to your torso.
- Pause for a brief second at the top, then slowly lower your legs until your heels lightly touch the floor or hover just above it, stopping sooner if your lower back starts to arch.
- Repeat for the desired number of repetitions.
Common Mistakes
Arching the Lower Back
Not keeping the lower back in contact with the ground can lead to discomfort and reduced effectiveness.
Using Momentum Instead of Control
Swinging the legs instead of lifting them in a controlled motion reduces ab activation and increases injury risk.
Dropping the Legs on the Way Down
Letting the legs fall back to the floor instead of lowering them under control gives up tension at the bottom of the rep, where the lower back is most likely to arch, so touch the floor lightly or stop just above it.
Letting the Knees Bend
Bending the knees as the legs rise or as fatigue sets in shortens the lever and makes the rep easier, so keep the legs straight or switch to a bent-knee version on purpose.
Holding the Breath
Breathing improperly can lead to unnecessary tension, so exhale as you lift and inhale as you lower your legs.
Injuries
Lying Leg Raise is a low risk exercise when performed with proper technique. It uses only body weight, and you can bend the knees or shorten the range at any point, but improper form can lead to strain, especially in the lower back. The hip flexors are the prime movers of the exercise, and that is where the risk comes from. The iliopsoas attaches to the lumbar spine and pelvis, so as it lifts and lowers straight legs it also pulls the pelvis into a forward tilt and arches the lower back unless the abdominals hold it in place. That pull is strongest when the legs are low and the lever is longest, so the lower back is most exposed at the bottom of the range, not when the legs point straight up.
Letting the lower back arch excessively can cause discomfort and potential strain. Engaging the core and keeping the lower back pressed against the floor helps prevent this. The job of the abs here is to hold the pelvis still while the hip flexors move the legs, so feeling the hip flexors work hard is normal and not a sign of bad form. Lower the legs only as far as you can keep the lower back down, and if it starts to lift before the heels reach the floor, stop the descent at that point and raise the legs again. Focus on controlled movement and avoid excessive swinging, since letting the legs drop quickly carries them straight into the range the abs can least control. Raising the head off the floor unnecessarily may cause neck strain. Keep the head and upper body relaxed.
To regress the movement, bend the knees to shorten the lever, which turns it into a Lying Knee Raise, or keep the legs straight but stop well short of the floor. Sliding the hands, palms down, under the hips can also make it easier to keep the pelvis from tipping forward. Reverse Crunch is another good regression, since the bent knees keep the lever short. If you have back pain that predictably flares with leg raises, switch to Dead Bug, Plank and Side Plank, which train the abs without the long-lever pull on the lower back. Once 12 to 15 slow reps with a flat lower back are easy, progress to Medicine Ball Lying Leg Raise, then to Hanging Knee Raise and Hanging Straight Leg Raise.
Stop the set if you feel sharp pain in the lower back, pain, tingling or numbness running into a leg, or a pinching pain at the front of the hip. Also end the set when the lower back keeps lifting off the floor even with a shorter range, because at that point the abs can no longer control the pelvis and further reps mostly add strain to the lower back.
- Primary Focus
- Core
- Equipment
- Body weight
- Modality
- Strength
- Difficulty
- Beginner
Alternative Exercises
Frequently Asked Questions
- Q: Is this exercise good for lower belly fat?
No. The lying leg raise strengthens the abdominal muscles, but it does not burn the fat sitting over them, and no exercise strips fat from the area it trains. Belly fat comes down with overall body fat, which is driven by an energy deficit across diet and total daily activity.
- Q: How many reps should I do for best results?
Aim for 10 to 15 controlled reps per set, adjusting based on your fitness level. Once 15 clean reps with a flat lower back feel easy, make the exercise harder, for example by slowing the lowering phase or moving to the Hanging Straight Leg Raise, rather than adding more reps.
- Q: Can I modify this exercise if I find it too hard?
Yes. If full leg raises are too difficult, try bending the knees slightly or performing a single-leg raise to reduce strain while still engaging the core. The Lying Knee Raise shortens the lever further and makes a good stepping stone.
- Q: Does the lying leg raise really work the lower abs?
Yes, to a modest degree. The rectus abdominis is one continuous muscle with no separate lower ab to isolate, although its lower region does a little more of the work in leg raises than in a crunch. To shift the emphasis further, the Reverse Crunch curls the pelvis up toward the ribs.
- Q: Why does my lower back lift off the floor during leg raises?
The hip flexors that lift the legs attach to the lumbar spine and pelvis, so when the abs cannot hold the pelvis steady against the pull of straight legs, the pelvis tips forward and the lower back arches. The pull is heaviest when the legs are close to the floor, so lower them only as far as you can keep your back flat, or bend the knees to shorten the lever.