Leg Raise

The leg raise is one of the most widely used bodyweight ab exercises, popular precisely because it needs no equipment and is often marketed as the best way to hit your “lower abs.” Lie on your back, keep your legs straight, and lift them to vertical while your abs fight to keep your pelvis from tilting and your lower back from arching — that fight against an arching spine, not the height of your legs, is what actually trains your core. This guide covers exactly how to do the leg raise with good form, what the muscles really do (including the nuance behind the “lower ab” claim), the mistakes behind most of the back pain people blame on it, and the variations worth adding once a clean set of bodyweight reps feels easy.

What muscles does the leg raise work?

The leg raise is often marketed as a “lower ab” exercise, but the rectus abdominis is one continuous sheet of muscle with no separate upper and lower halves. What the research actually shows is mixed: a 2023 ultrasound study found the leg raise biases muscle thickness change toward the lower abdominal segment more than a crunch does, while an older EMG study found no significant difference between upper and lower rectus abdominis activity across several ab exercises. What's not in dispute is that the hip flexors — mainly the iliopsoas — do most of the actual work of lifting the legs, while the abdominal wall works largely isometrically to stop your pelvis tilting forward and your lower back arching off the floor.

How grip and angle change muscle activation

Research on the leg raise's muscle activation is more nuanced than the “lower ab exercise” marketing suggests. Treat these as approximate, study-specific findings rather than universal numbers.

• Leg raise vs. crunch (ultrasound): A 2023 study found the crunch produced roughly 36% greater rectus abdominis thickness change than the leg raise, and a sit-up roughly 32% greater — a lower-intensity abdominal stimulus by this measure.
• Segmental bias: The same study found the leg raise biased activation toward the lowest abdominal segment measured, while the crunch biased the topmost segment — mild regional emphasis, even though it's one muscle.
• Older EMG evidence: A 2003 EMG study of six ab exercises found no significant difference between upper and lower rectus abdominis activity for any exercise tested, including a leg-lowering movement.

Based on EMG research. [3]

How do you do the leg raise?

To do the Leg Raise: lie flat on your back on a mat with your legs straight and together, and your arms flat at your sides, palms down; press your lower back into the floor by drawing your belly button toward your spine — this is your starting brace; keeping your legs straight and together, exhale and raise them until they're pointing straight up toward the ceiling; pause briefly at the top without letting your hips rock or your lower back lift off the floor.

1. Lie flat on your back on a mat with your legs straight and together, and your arms flat at your sides, palms down.
2. Press your lower back into the floor by drawing your belly button toward your spine — this is your starting brace.
3. Keeping your legs straight and together, exhale and raise them until they're pointing straight up toward the ceiling.
4. Pause briefly at the top without letting your hips rock or your lower back lift off the floor.
5. Inhale and lower your legs back down under control, stopping a few inches above the floor to keep tension on your abs.
6. Repeat for your target reps without letting your heels touch down or your lower back arch off the mat between reps.

What are the key leg raise form cues?

Lower-back contact

Keep your lower back pressed flat into the floor for the entire set — the instant it arches, your hip flexors have taken over and your abs are out of the movement.

Leg lockout

Keep your knees fully extended (or a very slight micro-bend) and your legs squeezed together — bent knees shorten the lever and make the rep easier.

Pelvic tilt

Actively tuck your pelvis under before you start lifting — this pre-braces your lower abs before your hip flexors take the lead.

Descent speed

Slow the lowering phase down more than the lift — the eccentric on the way down is where most of the ab-specific benefit happens.

Hand position

Keep your hands flat under your glutes or lower back if you can't yet keep it pinned to the floor, and move them to your sides once you can.

Breathing & tempo: Exhale as you raise your legs to keep your core braced against the load, and inhale on the way down. A roughly 1–2–2 tempo — about 1 second up, a brief pause at the top, and a slower 2-second lower — keeps tension on the abs instead of letting momentum do the work.

How should you warm up for the leg raise?

The leg raise needs little dedicated warm-up, but priming your hip flexors and finding a neutral pelvis first makes the set more productive: spend 30–60 seconds on a few cat-cow reps or a posterior pelvic tilt drill, then do one light set of 5–8 slow, partial-range leg raises before your working sets to groove the brace.

What are the most common leg raise mistakes?

• Letting the lower back arch off the floor — Posteriorly tilt your pelvis and brace before you lift, and stop the rep the instant a gap opens under your lower back — that's the point your hip flexors have taken over.
• Using momentum to swing the legs up — Slow the whole rep down, especially the lowering phase, and stop a few inches above the floor instead of letting your feet drop and bounce back up.
• Bending the knees to cheat the range — Keep your legs straight and together for the standard version, or deliberately regress to a bent-knee raise until you're strong enough to keep them straight.
• Chasing the highest possible leg position — Stop the ascent at whatever height you can control without your lower back lifting — for many beginners that's well short of vertical, and that's fine.
• Holding your breath through the set — Exhale on the way up and inhale on the way down; holding your breath spikes pressure in your midsection without adding useful tension.

Why does the leg raise hurt — and how do you fix it?

Discomfort during the leg raise almost always comes from letting the hip flexors take over a movement meant for your abs, not from the exercise itself. Match your symptom to the likely cause below, and see a professional if pain is sharp, radiating, or doesn't resolve once you fix your setup.

How many sets and reps should you do?

Choose your sets and reps by goal: heavier and fewer reps for strength, moderate for muscle size, lighter and higher for endurance.

RPE / RIR: Rate the last few reps of the set, not the whole thing — once you can't keep your lower back flat on the floor without your form breaking down, you're at RPE 9–10 and the set should end there. Most working sets should land around RPE 7–8, leaving a couple of clean reps in reserve rather than grinding until your back arches.

Progress the leg raise by first mastering full-range reps with a flat lower back, then adding reps within the 10–15 range, then slowing the tempo (especially the eccentric), and only then adding external load with ankle weights or a dumbbell held between your feet. Chasing more reps before your lower back stays flat just reinforces the exact compensation pattern you're trying to train out.

How often should you leg raise and where does it fit?

Train the Leg Raise 2–4 sessions per week, placing it near the end of a session as a finisher, after your main compound lifts.

• Frequency: 2–4 sessions per week
• Best split days: Core finisher after any training day, Dedicated ab/core day, Light activation drill in the warm-up
• Where to place it: Near the end of a session as a finisher, after your main compound lifts

Because it's low-fatigue and equipment-free, the leg raise tolerates higher frequency than heavy compound lifts — just watch total volume if your hip flexors are already loaded elsewhere that week, from sprinting, squats, or running.

How do you progress the leg raise?

Add reps within your target range first, then slow the tempo down (especially the lowering phase), and only add external load once you can perform 15–20 slow, controlled reps with your lower back glued to the floor for every single rep.

What's the right range of motion?

The leg raise's range runs from legs flat on the floor to vertical, perpendicular to your torso — but your real usable range is only as long as you can keep your lower back flat against the floor. Stopping short of vertical with a flat back builds more usable core strength than reaching full height with an arched lower back.

What are the benefits of the leg raise?

• Trains the rectus abdominis and hip flexors together through a full range of hip flexion, using only bodyweight
• Needs no equipment and can be done almost anywhere in the time it takes to lie down
• Builds the pelvic control and anti-extension core strength that carries over to heavier compound lifts like the squat and deadlift
• Scales cleanly from a bent-knee beginner version to a weighted or hanging advanced variation
• Reinforces the posterior pelvic tilt and braced core position used to protect the lower back under load

Who should do it: Beginners building a first core routine, lifters who want to train hip flexion and lower-ab control without equipment, and anyone working on the pelvic-tilt awareness that protects the lower back during heavier lifts. It's a poor fit for anyone with current lower-back pain or very tight, dominant hip flexors until they can keep their lower back flat through the full set — start with a bent-knee or single-leg version instead.

Is the leg raise safe?

The leg raise is safe for most healthy adults when the lower back stays flat against the floor and the range of motion stops the moment that contact breaks. The main risk isn't the exercise itself — it's letting fatigued abs hand the job to the lower back, which arches under the pull of the hip flexors.

Current or recent low-back pain

Get cleared by a physical therapist first, and start with a bent-knee or single-leg raise through a short range you can control, rather than the full straight-leg version.

Tight or dominant hip flexors

Expect to feel this exercise more in your hips than your abs at first — pair it with hip flexor mobility work and focus on the posterior pelvic tilt cue rather than chasing height.

Pregnancy (second/third trimester)

Supine exercises that compress the abdomen for extended periods are generally discouraged later in pregnancy — ask your provider about side-lying or standing core alternatives.

How do grip and stance change the leg raise?

• Hands at sides, palms down (standard): Balances stability and difficulty for most lifters.
• Hands under glutes / lower back: Gives direct feedback and support for the pelvis — an easier regression for beginners.
• Hands overhead or holding a fixed support: Removes the stabilizing base your hands provide, increasing the core-control demand.
• Legs neutral vs. slightly turned out: A neutral, hip-width stance is standard; a slight external rotation can subtly bias the hip flexors and inner thigh.

Leg Raise variations

How does the leg raise compare?

Leg Raise vs. Crunch

A 2023 ultrasound study found the crunch produces roughly 36% more rectus abdominis thickness change than the leg raise, but biases the upper segment; the leg raise biases the lower segment and trains a longer range of hip flexion. Most core routines benefit from both.

Leg Raise vs. Reverse Crunch

The reverse crunch curls the hips and pelvis off the floor, putting more work directly on the abs; the leg raise keeps the pelvis still and relies more on the hip flexors. If leg raises feel mostly like a hip exercise, the reverse crunch is a useful abs-biased swap.

Leg Raise vs. Hanging Leg Raise

The floor version gives direct feedback — the moment your lower back lifts off the mat, you've lost the brace. The hanging version removes that feedback and adds a real grip and shoulder-stability demand, making it a harder progression rather than a straight swap.

Leg Raise alternatives

How many calories does the leg raise burn?

Calories depend on your bodyweight and how hard you train. Resistance training has a MET value of about 3.5. Enter your bodyweight and minutes to estimate the burn (calories = MET × kg × 3.5 ÷ 200 × minutes).

Leg Raise strength standards

The leg raise isn't a loaded lift, so instead of a bodyweight-multiple table, use clean consecutive reps in one set as your benchmark — an informal fitness benchmark rather than a single peer-reviewed norm.

By age: Core endurance holds up better with age than maximal-strength lifts do; a consistent routine can maintain most of these benchmarks well past your 40s and 50s, especially using the bent-knee regression.

What counts as a good rep?

A leg raise rep counts when your legs start together and straight (or with a fixed, controlled knee bend for the easier version), rise under control without swinging, and your lower back stays in contact with the floor for the entire rep. A rep where your lower back lifts off the floor to gain height doesn't count as clean, even if your legs reach vertical.

References

1. How to Do Lying Leg Raise: Muscles Worked & Proper Form. StrengthLog
2. How To Do Leg Lifts Properly: A Step-by-Step Guide. Cleveland Clinic
3. Gomirato AP, Grenier SG. Diagnostic Ultrasound Shows Preferential Activation of Rectus Abdominis Segments with Exercises Targeting Upper Versus Lower Segments. International Journal of Exercise Science (NIH / PMC), 2023
4. Clark KM, Holt LE, Sinyard J. Electromyographic comparison of the upper and lower rectus abdominis during abdominal exercises. Journal of Strength and Conditioning Research, 2003
5. ExRx.net: Lying Leg Raise (on floor). ExRx.net
6. Herrmann SD, et al. 2024 Adult Compendium of Physical Activities: A Third Update of the Energy Costs of Human Activities. Journal of Sport and Health Science (NIH / PMC), 2024
7. Anatomy, Bony Pelvis and Lower Limb, Iliopsoas Muscle. StatPearls (NCBI Bookshelf)
8. Yoo W. Effect of modified leg-raising exercise on the pain and pelvic angle of a patient with back pain and excessive lordosis. Journal of Physical Therapy Science (NIH / PMC), 2017