Leg Raises vs Sit Ups: Which Move Actually Builds Abs?

You walk into any gym, and you see two camps. On the mats, people are cranking out sit-ups by the dozen. Over by the pull-up bars or benches, others are strictly focused on lifting their legs. It begs the question: in the battle of leg raises vs sit ups, which exercise actually deserves a spot in your routine?

It isn't just about which one burns more; it's about biomechanics, spine health, and targeting the specific fibers you want to pop. If you choose wrong, you might end up with tight hip flexors and a sore lower back rather than a chiseled core. Let's break down the mechanics, the risks, and the rewards of both movements.

Quick Summary: The Verdict

If you are looking for a fast answer to settle the debate, here is the breakdown of how these two movements compare:

• Target Area: Sit-ups primarily target the upper rectus abdominis. Leg raises focus heavily on the lower abs and hip flexors (iliopsoas).
• Spinal Health: Sit-ups involve spinal flexion (rounding), which can aggravate disc issues. Leg raises require a neutral spine, making them generally safer for the back if you keep your lower back pressed to the floor.
• Hypertrophy: Leg raises (especially hanging variations) generally offer higher tension potential for muscle growth than high-rep sit-ups.
• The Winner: For pure aesthetic ab development and safety, leg raises usually win. For functional hip mobility and military testing standards, sit-ups take the lead.

The Sit-Up: Old School Standard or Outdated?

The sit-up is the grandfather of ab exercises. It is a compound push movement for the core that involves lifting your entire torso off the floor towards your knees.

The Mechanics

When you perform sit-ups vs leg raises, you are engaging the rectus abdominis to flex the spine. However, once your torso passes about 30 degrees of elevation, your abs largely become stabilizers, and your hip flexors take over to pull your body the rest of the way up.

The Downside

The main criticism of the sit-up is the compressive load it places on the lumbar spine. Repeated spinal flexion under load can be a mechanism for disc herniation. Furthermore, if you anchor your feet (hooking them under a couch or having a partner hold them), you are essentially turning the move into a hip flexor workout, minimizing the work your abs actually do.

Leg Raises: The Lower Ab Specialist

Whether performed lying on the floor (leg lifts) or hanging from a bar, this movement is often cited as the superior choice for the elusive "lower abs."

The Mechanics

In the debate of leg lifts vs sit-ups, leg raises work from the bottom up. Your goal is to flex the hips while maintaining a stable core. The rectus abdominis works isometrically to keep your pelvis neutral. If you curl your pelvis up at the top of the movement (a reverse crunch), you actively engage the lower fibers of the abs.

The Hidden Risk

Leg raises are not foolproof. The most common error is allowing the lower back to arch (anterior pelvic tilt) as the legs lower. If your back peels off the floor, your abs have failed, and the heavy weight of your legs is now hanging directly off your lumbar spine. This is a one-way ticket to back pain.

Comparing Hypertrophy and Strength

So, which builds muscle faster?

Time Under Tension

Leg raises, specifically hanging leg raises, allow for greater progressive overload. You can hold a dumbbell between your feet or simply straighten your legs to increase the lever arm. Sit-ups are harder to load progressively without awkward positioning (like holding a plate behind your head).

Muscle Isolation

If you want to isolate the "six-pack" muscle, neither is perfect, but leg raises are generally superior because they discourage the momentum often used in sit-ups. Sit-ups are notorious for being cheated—people throw their arms forward or jerk their torso up, removing tension from the muscle.

My Personal Experience with Leg Raises vs Sit Ups

I have cycled through just about every core program out there, from military-style calisthenics to bodybuilding isolation. Here is the reality regarding these two movements that the textbooks don't tell you.

When I was doing high-volume sit-ups (we're talking 100+ reps a session), the limiting factor wasn't my abs—it was the skin on my tailbone. Even with a yoga mat, I'd get this raw, carpet-burn-like abrasion right above the glutes, known in the gym as a "raspberry." It made showering afterward a nightmare. Plus, my hip flexors would get so tight that my squat depth suffered the next day.

Switching to hanging leg raises changed the game, but the learning curve was annoying. At first, my grip failed before my core did. I also remember the specific, uncomfortable "click" in my right hip socket whenever I lowered my legs too fast. I had to learn to slow down the eccentric (lowering) phase to a 3-second count. Once I did that, the clicking stopped, and the lower ab soreness the next morning was unlike anything I got from sit-ups.

Conclusion

The battle of leg raises vs sit ups comes down to your injury history and your goals. If you need to pass a military fitness test, you have to do sit-ups. But if you want a strong, aesthetic core without grinding your lumbar spine, leg raises are the smarter investment.

Start with lying leg raises. Once you can do 15 reps with your lower back glued to the floor, graduate to the hanging bar. Your spine will thank you.

Frequently Asked Questions

Are leg raises better for back pain than sit-ups?

Generally, yes. Sit-ups involve repetitive spinal flexion which can aggravate discs. Leg raises keep the spine neutral, provided you have the core strength to keep your lower back flat against the floor or backrest.

Can I do both leg raises and sit-ups in the same workout?

You can, but it is often redundant. Since both movements heavily involve the hip flexors, doing them back-to-back can lead to tightness. It is better to pair one of these movements with a stabilization exercise, like a plank or an ab wheel rollout.

Do leg raises burn belly fat?

No exercise can spot-reduce fat. While leg raises strengthen and build the muscle underneath, revealing those muscles requires a caloric deficit to lower your overall body fat percentage.