The Leg Raise: A Complete Guide From First Rep to Advanced Variations
Also called Straight Leg Raise, Lying Leg Raise
Quick Intro
The leg raise is a core exercise performed lying on the back, lifting both straight legs from the floor to roughly 90 degrees and lowering them back down under control.
Equipment Needed
None. A leg raise needs nothing but floor space to lie down on, though a mat adds comfort for the lower back.
Why the Leg Raise Matters
The leg raise loads the abs (rectus abdominis) and hip flexors (iliopsoas) through a long lever: keeping the legs straight instead of bent, as in the Reverse Crunch, means the weight being lifted sits much further from the hip joint. Your deep core stabilizer (transverse abdominis) works throughout to keep the lower back pinned to the floor as the legs move.
That long lever is what separates this exercise from most other floor-based core work. The hip flexors do a large share of the lifting here, while the abs work isometrically to stop the pelvis from tilting and the lower back from arching off the floor. A leg raise that lets the back arch has quietly shifted from a core exercise into a hip flexor exercise with a sore lower back attached.
The leg raise is a demanding muscular strength and endurance exercise for the abs and hip flexors. Controlling the straight-leg lever carries a body composition benefit as well.
When to Do It
The leg raise fits well in a core-focused segment, ideally somewhere before fatigue has already worn down the lower back’s ability to stay pinned to the floor. Two to four sessions a week is reasonable, since the hip flexors need real recovery time between sessions.
- An existing lower back issue. The long lever this exercise uses places real demand on lower back control, and a back that’s already arching or aching will struggle to keep the spine pinned down. Building a foundation with Reverse Crunch or Dead Bug first, and only lowering the legs as far as the back stays flat, is the safer approach.
For most people without an active back issue, the leg raise is a strong, equipment-free way to train the lower abs and hip flexors together.
Getting Ready
A minute of gentle spinal movement, like a few rounds of Cat-Cow, loosens the lower back before this exercise asks it to stay still under load.
Press the lower back into the floor before lifting, and keep it pinned there for the whole set. The moment the back lifts off the floor and arches is the actual range limit for that day, not a point to push through.
Step-by-Step Instructions
1. Starting position. Lie flat on your back with your legs straight and together, arms at your sides or tucked under your lower back for support.
2. The lift. Keeping your legs straight, lift them together until they reach roughly 90 degrees, hips still flat on the floor.
3. The lower. Lower your legs back down under control, stopping the moment your lower back starts to arch off the floor.
Repeat for the full set, treating the point where the back wants to arch as the actual bottom of the range for that day.
How Many, How Often
| Level | Where you’re at | What to do |
|---|---|---|
| Beginner | New to the movement | 3 sets of 8 to 10 reps, resting 1 minute between sets. A smaller range, stopping well before the back arches, is fine while building control. |
| Intermediate | 15 clean reps come easily | 3 to 4 sets of 15 reps, or add a 1 second pause with the legs at the top of the lift. |
| Advanced | 20 or more clean reps come easily | Slow the tempo to a 3 second lower on every rep, since more reps at a normal speed add little new strength at this point. |
Letting the lower back arch off the floor is the easiest way to squeeze out a few extra inches of range while quietly training the hip flexors alone, so keeping the back pinned matters more here than reaching a full 90 degrees.
Modifications and Variations
The leg raise has a clear easier step and a clear harder one.
For an easier entry point, the Reverse Crunch bends the knees instead of keeping the legs straight, shortening the lever and reducing how much load the lower back has to resist.
The natural next step up is the Hanging Leg Raise, performed from a pull-up bar. Removing the floor entirely adds a grip and shoulder demand on top of the same core work.
Progression path: Reverse Crunch → Leg Raise → Hanging Leg Raise
Move to the next step once a full set feels controlled, with the lower back staying flat for every rep.
Common Mistakes to Avoid
Letting the lower back arch off the floor. This is the fault that defeats the exercise’s purpose, since an arched back means the hip flexors have taken over from the abs entirely. Stopping the lower at the point where the back wants to lift keeps the work honest.
Using momentum to swing the legs up. A fast kick at the bottom of the rep borrows speed the exercise isn’t meant to reward. A slow, deliberate lift keeps the abs and hip flexors doing the work.
Bending the knees to cheat the range. Letting the knees bend partway through the lift shortens the lever and makes the rep easier without training the same straight-leg demand. Keeping the legs straight, or switching to the Reverse Crunch on purpose, keeps the rep honest either way.
Holding the breath through the whole set. Bracing hard and forgetting to breathe adds unnecessary tension and fatigue. A steady exhale on the lift and inhale on the lower keeps the set sustainable.
After Your Set
A set of leg raises puts real, sustained demand on both the hip flexors and the lower back. Kneeling with the back knee down and gently shifting the hips forward releases the muscle that did most of the lifting. Hugging both knees to the chest for a few slow breaths gently decompresses the lower back after holding it pinned to the floor.
Going Deeper
The leg raise sits above the Reverse Crunch as the straight-leg version of the same lifting pattern, usually placed early in a core segment while the lower back can still hold a flat position reliably. It pairs well with a rotational core exercise like the Russian Twist in the same session, since together they cover flexion and rotation without repeating the same movement twice.
Progress on the leg raise tends to stall for one specific reason: the range of motion quietly shrinking as the lower back starts arching earlier and earlier in the set, which lets someone finish the rep count while the abs do less real stabilizing work each time. The fix is trusting a smaller, honest range over a bigger one that costs the lower back its position, and rebuilding range gradually as control improves.
Eight clean reps with the back staying flat usually arrive within the first two to three weeks, and fifteen clean reps to a full 90 degrees somewhere in the five to seven week range after that.
How to Know You’re Improving
Four checkpoints mark real progress on the leg raise:
- Eight clean reps with the lower back staying flat on the floor
- Fifteen clean reps reaching a full 90 degrees
- A 1 second held top position for a full set
- A 3 second controlled lower on every rep of a full set
A rep counts as clean when the lower back never lifts off the floor, the legs stay straight throughout and the lower happens under control rather than dropping. Keeping that flat back from the first rep to the last matters far more than how high the legs actually swing.
Muscles Worked
- Rectus Abdominis (the abdominal muscles running down the front of the stomach, holding the pelvis down so the lower back stays flat)
- Iliopsoas (the deep hip flexor at the front of the hip, lifting the straight legs from the floor)
- Transverse Abdominis (a deep core muscle that wraps around the torso like a corset, bracing the trunk against the legs’ leverage)
FAQ
Why does my lower back arch during a leg raise? This usually means the hip flexors are strong enough to lift the legs before the abs are strong enough to keep the pelvis stable. Shortening the range to where the back stays flat fixes it directly.
Is the leg raise better than a reverse crunch for abs? Neither replaces the other. The straight-leg lever here demands more from the hip flexors and lower back control, while the Reverse Crunch shortens that lever and is more approachable for a beginner.
Can I do leg raises every day? Given the real demand this exercise places on the hip flexors, two to four sessions a week with rest between them works better for most people than daily training.
What’s the difference between a leg raise and a hanging leg raise? The floor version keeps the lower back’s contact with the ground as a built-in check on form, while a hanging leg raise removes that floor and adds a real grip and shoulder demand.
Next in this series: the Russian Twist, a rotational core exercise that pairs naturally with this one.