How to Do Leg Raises: Form Guide, Muscles Worked & the Lying vs Hanging Truth

Crunches, sit-ups, and most gym-class abs work train the core from the top down: the ribcage curls toward the pelvis. Leg raises attack from the other end - the legs move at the hips while the abs fight to hold the pelvis and spine still. That reversed job is exactly what many programs are missing.

Three things make leg raises worth programming:

• Lower-ab emphasis without repeated spinal flexion: unlike sit-ups, which flex the lumbar spine rep after rep, the lying leg raise keeps the spine close to neutral while the lower fibers of the rectus abdominis control the pelvis - a genuinely different stress for the same muscle sheet.
• Pelvic control that carries over: the skill of stopping your pelvis from tipping forward under load is the same skill that protects your spine in squats, deadlifts and sprints.
• Zero equipment and a built-in difficulty dial: the floor version needs only a mat, and the same pattern scales all the way to hanging from a bar - one of the few core movements with a years-long progression.

The honest caveat: done sloppily, leg raises quietly turn into a lower-back exercise - the hips lift, the lumbar spine arches, and the psoas pulls on the very vertebrae you were trying to protect. The form section below is where that gets fixed.

The lying leg raise looks like one simple hinge, but the exercise lives or dies on the last few inches before the floor. Here is the sequence, floor to finish.

Step 1 - Setup: Lie on your back with legs together and nearly straight, heels a few inches off the floor to start. Place your hands palms-down under the sides of your hips or flat on the floor beside you - never behind your head, because a bracing yank on the neck is the most common beginner error. Keep your head and shoulders heavy on the mat.

Step 2 - The raise: Exhale and brace your abs as if bracing for a light punch, then lift your legs smoothly toward vertical, moving only at the hips. The toes stay relaxed, the knees stay almost straight, and the pelvis stays glued to the floor. Reaching vertical is not required - raise only as high as you can without the pelvis rolling up behind you.

Step 3 - The lowering: This is the actual exercise. Lower your legs on a slow 3-4 second count, and stop the moment your lower back begins to arch off the floor - for most people that is somewhere between 15 and 45 degrees above the floor. That point is the true end of your range today; the abs are no longer holding the pelvis, and everything past it is lumbar spine doing someone else's job.

Step 4 - Breathing and tempo: Exhale as the legs rise, inhale as they fall, roughly 2-3 seconds up and 3-4 seconds down. In my experience coaching beginners, two tells expose a broken leg raise every time: toes that race to the floor (tempo too fast to control the pelvis) and a back that arches while the legs are still high. Both have the same fix - bend the knees to shorten the lever and rebuild the range slowly, the same way you would regress crunches when the neck takes over.

A note on volume: 2-3 sets of 8-15 controlled reps beats a daily hundred, and the first quality to earn is not height but a silent, still pelvis.

A leg raise is a hip-flexion movement wearing an ab costume. Knowing who does what changes how you use it:

Muscles Worked

• Hip flexors (the engine): the iliopsoas and rectus femoris lift the legs at the hip. These are strong muscles doing the visible work - if you feel leg raises mostly in the front of your hips, that is anatomy, not bad form.
• Rectus abdominis, lower fibers (the brakes): the abs do not lift the legs - they prevent the pelvis from tipping forward as the legs lower. The eccentric fight to keep the lumbar spine flat is the part that feels like "lower ab" work.
• Obliques and deep stabilizers: the obliques and transverse abdominis keep the pelvis and ribcage level from side to side, which is why the legs want to wobble as fatigue builds.

The Lower-Ab Truth

The rectus abdominis is one sheet of muscle with one leash of connective tissue - you cannot contract only its lower half, and "lower abs" as a separate muscle does not exist. What you can do is bias the lower fibers: leg raises load the abs exactly where those fibers attach, at the pelvis. That is why they complement crunches (which load the abs from the ribcage end) instead of duplicating them. As for visibility - whether any of this shows - that is a body-fat question with an unpopular answer, covered honestly in the FAQ below.

Same pattern, two difficulty worlds. The lying version lets the floor hold your pelvis honest; the hanging version removes the floor and makes your whole body earn the rep.

Which is "better" depends on where you are. The classic San Diego State EMG study commissioned by the American Council on Exercise ranked the captain's chair - essentially hanging knee raises - among the top exercises for both the rectus abdominis and the obliques, so the ceiling is clearly higher when you hang. But the hanging version has no honest regression once form breaks, while the lying version tells you the moment your pelvis quits. The efficient path is not choosing a camp: build 15 controlled lying reps with a still pelvis, then progress through bent-knee hanging raises to straight legs. The bent-knee lying raise, for the record, is also the right starting point if your back is sensitive - the shorter lever cuts the torque on the lumbar spine dramatically while training the identical skill. Pair the whole progression with planks (anti-extension) and you have both directions of core strength covered in one short session.

Here is the evidence-based middle ground between "leg raises are a spine wrecker" and "they never bothered anyone".

The concern is real: the psoas - the strongest hip flexor - attaches directly to the lumbar vertebrae. Every rep where the pelvis tips forward and the lower back arches off the floor puts those vertebrae under loaded extension while the psoas pulls on them, and spine researchers have spent decades documenting what thousands of such cycles cost intervertebral discs. People with desk-shortened hip flexors and weak deep abs are doing exactly this without realizing it, because the arch is subtle and the rep still "feels" finished.

The panic is overblown: controlled-range leg raises are a standard rehabilitation tool, not a threat - exercise in general, and structured core stability work in particular, is one of the best-supported treatments for chronic low back pain in systematic reviews. The people who get hurt are almost never doing 8-15 controlled reps; they are racing daily rep challenges with an arched back and no range awareness.

Practical rules that keep leg raises spine-friendly:

• Find your end range and respect it: the moment the lower back arches, the rep is over - today. Range grows with strength, not willpower.
• Hands under the hips: a small pelvic tilt backward before the first rep pre-positions the lumbar spine flat and gives you instant feedback through your hands.
• Brace before the legs move: exhale and set the abs first, then lift. Legs leading a soft trunk is the arch in the making.
• Counterbalance the flexion-bias: if you sit all day, pair leg raises with mountain climbers for conditioning or glute bridges for extension so the hips are not only ever working in one direction.
• Who should regress first: anyone with an active disc problem, spondylolisthesis, or physician-advised spinal precautions should start with the bent-knee version and a shortened range, and treat planks as the default core tool until cleared.