Stop mindlessly flailing your legs. Seriously. If you’ve spent any time in a gym or scrolling through fitness TikTok, you’ve seen it: someone lying on a mat, back arched like a bridge, legs swinging wildly while their lower back screams for mercy. It’s painful to watch. Most people treat the leg raise as a momentum-based hip flexor exercise, which is exactly why they never see that lower abdominal definition they’re chasing.
Doing proper leg raises isn't just about moving your feet from point A to point B. It’s a game of spinal mechanics. If your spine isn't in the right position, you’re basically just training your psoas to be tighter than a guitar string, which leads to that nagging lower back ache many lifters complain about. You’ve probably felt it—that weird "click" in your hip or the dull pressure in your lumbar spine after a set of twenty. That is your body telling you that you're doing it wrong.
The reality is that "abs" aren't even the primary muscle responsible for lifting your legs. The rectus abdominis—the six-pack muscle—doesn't attach to your legs. It attaches to your pelvis. To make this an "ab" move, you have to focus on what your pelvis is doing, not just your feet.
The Biomechanics of Why Your Back Hurts
The biggest mistake is the "anterior pelvic tilt." When you lie down and lift your legs, gravity wants to pull your lower back off the floor. If your core isn't strong enough to resist that pull, your pelvis tilts forward, your back arches, and the hip flexors take over the entire movement.
When the hip flexors (specifically the iliopsoas) contract without the abs stabilizing the pelvis, they pull directly on the lumbar vertebrae. It’s a tug-of-war. Your back is the rope. You lose.
To do proper leg raises, you must master the Posterior Pelvic Tilt. Imagine trying to squish a grape hidden under the small of your back. If there’s a gap between your spine and the floor, you aren't doing a leg raise; you're doing a back-strain exercise. Dr. Stuart McGill, a leading expert in spine biomechanics, often emphasizes the importance of core stiffness and "bracing" to protect the spine. In the context of the leg raise, this means your abs must work harder to stay still than your legs work to move.
A Step-by-Step Guide to the Lying Leg Raise
Let's break it down. Forget the "three sets of twenty" mentality for a second and focus on one perfect rep.
The Set-Up: Lie flat on your back. Do not put your hands under your butt. I know, everyone does it. It’s a "cheat" that makes the exercise easier by tilting your pelvis for you. If you can't keep your back flat without your hands there, your legs are going too low. Keep your arms by your sides or hold onto something heavy behind your head for extra stability.
The Pin: Exhale all your air. Feel your ribs drop down toward your hips. Now, press your lower back into the floor. This is your "home base." If your back leaves this position at any point, the rep is over.
The Ascent: Lift your legs slowly. Keep them straight if you can, but a slight bend is fine if your hamstrings are tight. Think about pulling your belly button toward your spine as you lift.
The Critical Descent: This is where the magic (and the danger) happens. Lower your legs at a snail's pace. As your legs get closer to the ground, the lever arm gets longer, and gravity works harder to arch your back. This is the "sticking point."
The Hard Stop: Don't go all the way to the floor if your back starts to arch at 30 degrees. Stop there. That’s your current range of motion. Over time, as your deep core—the transverse abdominis—gets stronger, you'll be able to go lower.
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Hanging Leg Raises: The Elite Version
Once you’ve mastered the floor, you might feel the urge to move to the pull-up bar. Most people mess this up even worse. They swing. They use momentum. They look like a pendulum.
In a hanging leg raise, the goal isn't just to lift the legs; it's to curl the pelvis. If your legs go up but your butt stays pointing at the floor, you’re just doing hip flexors again. You want to think about "showing your butt" to the wall in front of you. This ensures that the lower abs are actually contracting to tilt the pelvis upward.
Pro Tip: To kill momentum, stop your legs slightly in front of your body at the bottom rather than letting them swing back behind your hips. This keeps constant tension on the midsection and prevents that annoying "swinging" rhythm that ruins the set.
Common Myths That Just Won't Die
We need to talk about "spot reduction." You cannot "burn belly fat" by doing a thousand leg raises. This is a physiological impossibility. Fat loss happens through a caloric deficit, usually managed via diet and total energy expenditure. Leg raises build the muscle underneath the fat. If you want those muscles to show, you need to handle your nutrition.
Another myth is that "more is better." It isn't. If you can do fifty leg raises, you aren't doing them with enough tension. Slow down. Add a pause at the bottom. Try a "hollow body hold" position. Ten slow, controlled reps are infinitely more valuable than fifty sloppy ones.
Variations for Every Level
Not everyone can do a straight-leg raise with a flat back on day one. That’s totally fine. Honestly, most beginners shouldn't even try.
- Dead Bugs: This is the "pre-requisite" for the leg raise. Lying on your back, knees bent at 90 degrees, lowering one leg at a time while keeping the back pinned. It teaches the brain how to stabilize the spine while the limbs move.
- Bent-Knee Leg Raises: By shortening the lever (bending your knees), you reduce the weight your abs have to stabilize. It’s a great way to build the "mind-muscle connection" without wrecking your lumbar discs.
- Single-Leg Raises: Lowering one leg at a time while the other stays pointed at the ceiling. This provides a "counter-weight" that makes it easier to keep your back flat.
The Role of the Breath
You've probably noticed that if you hold your breath, your stomach pooches out. This is called "valsalva," and while it’s great for a heavy squat, it’s not always the best for targeting the deep core in a leg raise.
Try this: Exhale as you lower your legs. It sounds counter-intuitive. But as you exhale, your diaphragm moves up and your deep abdominal wall (the TVA) naturally cinches in. This "vacuum" effect helps stabilize the spine from the inside out. If you find your stomach "doming" or "poofing" out in the middle—a sign of poor intra-abdominal pressure management—focus on a forceful exhale through pursed lips.
Nuance: It’s Not Just Your Abs
People forget that your lats and grip play a role in hanging variations. If your grip fails, your core workout is over. Using gym chalk or straps isn't "cheating" if the goal is abdominal hypertrophy. Similarly, when hanging, "engage" your lats by pulling your shoulder blades down and back. This creates a stable "frame" for your core to work from.
Actionable Steps for Your Next Workout
Instead of just adding leg raises to the end of your session when you're exhausted, try moving them to the beginning as a "core primer."
- Assess Your Range: Lie on the floor and lower your legs. Have a friend try to slide a piece of paper under your lower back. The moment that paper slides through, that is your "floor." Do not go deeper than that point in your training.
- The 3-Second Rule: Take three full seconds to lower your legs. Pause for one second at your lowest point. Take two seconds to lift.
- Frequency: Aim for 2-3 times a week. Like any other muscle, the abs need recovery. Destroying them every single day usually leads to overactive hip flexors and a grumpy lower back.
- The "Tuck" Finish: At the top of a lying leg raise, try to lift your tailbone one inch off the floor. This tiny "crunch" at the top ensures full recruitment of the lower fibers of the rectus abdominis.
Proper leg raises are a lesson in humility. You will likely have to reduce your reps and your range of motion. You might feel "weaker" at first. But the result—a rock-solid core and a spine that doesn't hurt when you get out of bed—is worth the ego hit. Start slow, pin your back, and stop swinging.