How to Do Leg Raises with Proper Form

Quick Facts: Leg Raises

Muscles Worked

Primary movers. The rectus abdominis works the whole time to hold your pelvis still and keep your lower back pressed into the floor against the lever arm of two long legs trying to pull the pelvis into anterior tilt. Its upper and lower portions work about equally: in an EMG study of the lying leg raise with the hands beside the trunk, upper and lower rectus abdominis activity was 20.7% and 21.7% of maximum voluntary contraction (Kim and Lee, 2016). The hip flexors (iliopsoas) do the lifting: they raise the legs toward the torso as they shorten and control them on the way down.

Secondary mover. The obliques, along the sides of your waist, work with the rectus abdominis to keep your pelvis level and your lower back pressed down, most of all as your legs lower toward the floor.

Pelvis position. Your hips and lower back stay on the floor for the whole set. Keeping the lower back pressed down, with the pelvis tilted slightly back, keeps the rectus abdominis working harder than letting the back arch. Breathe out as you lift instead of holding your breath.

Mechanism. Leg raises load the anterior core through hip flexion under a long lever. The longer the legs (knees straight), the longer the lever arm and the harder your abs have to work to keep the pelvis in posterior tilt. The load is greatest in the lower part of the range: once the legs pass vertical, they put almost no load on the hip flexors or abs. When the abs can no longer hold the pelvis, the lumbar spine arches and the load shifts from the abs to the lumbar vertebrae. That is why "keep the lower back flat" is the entire safety rule for this exercise. A bent knee shortens the lever and lowers the demand, which is why bent-knee leg raises are the universal regression.

Step-by-Step Instructions

1. Lie flat on your back. Find a firm, flat surface; a mat on the floor is ideal. Lie with your legs fully extended and together, toes pointed or feet flexed (either works). Place your arms at your sides with palms flat on the ground beside your hips. Rest your head on the floor, or prop your head and shoulders up a little on your forearms; either works as long as your lower back stays pressed down. Tip: if you want more support for your pelvis, you can slide your hands under your buttocks instead.
2. Press your lower back into the floor. This is the most important setup cue. Actively press your lower back into the ground by bracing your abs. You should not be able to slide a hand under your lower back. Maintain this flat-back position throughout every rep. Tip: keeping your lower back pressed into the floor the whole time is what keeps your abs working to hold your pelvis still.
3. Engage your core and lift your legs. Keeping your legs straight (a slight knee bend is fine) and together, slowly raise them toward the ceiling. Brace your abs and keep your lower back flat on the floor as your legs come up. Don't swing or use momentum. Tip: breathe out as you lift; do not hold your breath.
4. Lift to vertical (or as high as your form allows). Ideally, raise your legs until they're perpendicular to the floor (90 degrees). If your lower back starts to arch before you reach that point, that's your current range of motion. Work within it. Tip: keep your legs pressed together and lift them as one, straight and steady.
5. Start down without resting at the top. Begin lowering as soon as your legs point straight up. At vertical your legs put little load on your hip flexors and abs, so a pause there is a rest, not extra work. Going a little past vertical with your hips down is fine, but it adds no load. Tip: for a harder rep, pause for a second with your heels just off the floor, then lift again.
6. Lower with control. Slowly lower your legs back toward the ground, taking 2 to 3 seconds on the descent. Stop when your heels are a few inches off the floor, with your lower back still pressed down, then lift again without resting them on the floor. This is where most of the work happens. Don't rush it.

Common Mistakes

• Lower back arching off the floor. This is the most common and most dangerous mistake. When your lower back lifts, your abs have lost their hold on your pelvis and your lumbar spine bears the load. Press the lower back flat and reduce the range of motion if needed. Tip: if your back arches, bend your knees or shorten the range, and stop if your lower back hurts.
• Using momentum to swing legs up. Swinging bypasses the muscles you're trying to train. If you need momentum to lift, the exercise is too hard at that range; shorten it.
• Dropping legs too fast on the descent. The lower part of the range is where your legs load your abs and hip flexors the most. If you let gravity do the work, you waste half the rep. Lower slowly and with control.
• Resting your heels on the floor between reps. Setting your feet down gives your abs a break at the point where they work hardest. Stop with your heels a few inches up and lift again; touching down between reps is the easier option if you need it.
• Holding your breath. Breath-holding during core exercises spikes intra-abdominal pressure and can spike blood pressure. Exhale forcefully as you lift, inhale as you lower.
• Bending the knees excessively. A slight knee bend is fine, but a large bend shortens the lever and makes the exercise much easier. Aim for the straightest legs your core strength allows.

Variations

• Reverse crunches (easier, smarter starting point if your back hurts). Bend the knees and lift the pelvis off the floor at the top. The shorter lever cuts hip-flexor demand.
• Bent-knee leg raises (easier). Perform the same movement with knees bent at 90 degrees. This shortens the lever arm and reduces core demand. Ideal for beginners building foundational strength. Letting your heels touch the floor between reps is another way to make the standard version easier.
• Single-leg raises (easier). Raise one leg at a time while the other stays on the ground. Lifting one leg asks much less of your abs than lifting both, so treat it as a stepping stone toward the full two-leg version.
• Leg raises with hip lift. At the top of the movement, lift your hips off the floor by pressing your feet toward the ceiling. Adds a reverse crunch component.
• Hanging leg raises (harder). Perform the movement while hanging from a pull-up bar. A significant progression that adds grip strength demand and allows a greater range of motion.
• Weighted leg raises. Hold a light dumbbell or medicine ball between your feet. The added load makes each rep significantly more challenging.

When to Avoid or Modify Leg Raises

Leg raises are safe for most healthy adults, but several conditions warrant modification or substitution. Always consult your physician or physical therapist before starting or returning to a core training program, especially if you have any of the following.

• Acute lower-back pain or known disc pathology. Leg raises load the lumbar spine through hip flexion under a long lever. If your abs cannot hold the pelvis flat, the lumbar vertebrae take the load. Skip leg raises until the acute pain resolves and a PT clears you. Start instead with deadbugs and bird-dogs to rebuild deep-core control.
• First 6 to 8 weeks postpartum or active diastasis recti. The intra-abdominal pressure from holding two long legs against gravity can widen abdominal separation. Restore deep-core function first with diaphragmatic breathing, transverse abdominis activation, and bird-dogs or deadbugs. Reintroduce leg raises only at the bent-knee or single-leg level once the abdominal wall stays flat under load.
• Recent abdominal surgery (C-section, hernia repair, appendectomy). Get clearance from your surgeon. Most post-surgical protocols start with diaphragmatic breathing, then gentle bracing, then progressive loading. Leg raises sit late in that progression.
• Hernia (umbilical, inguinal, ventral). The pressure spike during the lift can worsen symptoms. Consult your physician about safe core alternatives.
• Pregnancy (second and third trimesters). Avoid supine positions for long durations (vena cava compression) and avoid high intra-abdominal-pressure movements. Switch to upright or side-lying core work; consult your provider.
• Pelvic-organ prolapse or pelvic-floor dysfunction. Leg raises generate strong downward pressure on the pelvic floor. Work with a pelvic-floor PT before adding them back.
• Hip flexor strain or chronic hip flexor tightness. Leg raises load the iliopsoas directly. If the hip flexors are inflamed, switch to reverse crunches until the irritation settles.

Related Exercises

• Same plane (anterior core flexion): Crunches, partial crunches, and reverse crunches work the same anterior core but from the shoulder end (crunches) or with the pelvis lifting (reverse crunches) instead of the legs.
• Rotational core pairing: Bicycle crunches add a rotation component to the same lying core work; commonly paired with leg raises in an ab circuit.
• Foundation for spinal bracing: Deadbugs and bird-dogs are the universal foundations. Build the deep-core control there before pushing leg raises hard. Deadbugs in particular train the exact pattern leg raises demand: pelvis locked in posterior tilt while the legs move.
• Easier regression: Reverse crunches and the bent-knee leg raise variation cut the lever arm and the hip-flexor demand. Use these if straight-leg raises trigger any back complaint.
• Advanced progression: Hanging leg raises add grip and a longer range of motion. The natural next step once 3 sets of 15 floor leg raises feel light.
• Glute foundation (often paired): Glute bridges train the hip-extension pattern that balances the hip-flexion bias of leg raises. Pair them so the front and back of the pelvis develop together.
• Posterior balance: Bird-dog crunch and the dynamic bird-dog progressions balance the anterior pulling pattern with posterior chain work.

How to Program Leg Raises

The rep and rest ranges below draw on the ACSM position stand on resistance training (Ratamess et al., 2009), which recommends 8 to 12 repetitions for beginners and, for muscular endurance, light loads for 10 to 25 or more repetitions with rests under 90 seconds. Leg raises are a low-load, high-control movement, so volume can be relatively high once form is solid. The constraint is always the lower back staying flat, not the rep count.

Where in your workout. Place leg raises at the end of a resistance-training session, not the beginning. Pre-fatiguing the core compromises spinal stability under heavier compound lifts and trades a small core stimulus for a real safety risk. Leg raises also fit well in a standalone "core finisher" alongside planks and bicycle crunches, or as part of a 5 to 10 minute daily core routine paired with deadbugs and bird-dogs.

Form floor over rep targets. End the set the moment your lower back starts to arch off the floor. A clean set of 8 reps with the lumbar spine pinned beats a sloppy set of 20 where the back is arching and the lumbar spine is taking the load. Volume is meaningless without the position.

How FitCraft Programs This Exercise

Leg raises are a core staple, but their placement and volume need to match your current ability. FitCraft uses a personalized diagnostic to set your starting point from day one, and the app adjusts your training as you progress.

In the app, the leg raise is an Intermediate exercise done with straight legs together and your palms flat beside your hips. The app's demo props the head and shoulders up on the forearms and stops with the heels about 8 inches up, a slightly easier range. Lowering until your heels are a few inches off the floor, as described above, keeps your abs working through the hardest part of the range.

Every program is grounded in exercise science and shaped by an Ivy League-trained exercise scientist and NSCA-certified strength coach.

FitCraft's gamification system (streaks and collectible cards) keeps you showing up for the core sessions that are easy to skip. Visible abs aren't built in one great workout. They're built by showing up consistently, week after week. That's what FitCraft is designed to make happen.