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Leg raises

Muscle:
abs
Equipment:
bodyweight

Why it's worth doing

Leg raises load the abs at an angle most core exercises don't touch: hip flexion against resistance, with the torso staying fixed instead of moving toward the legs the way it does in a classic crunch. That puts more emphasis on the lower portion of the rectus abdominis, the part that's hardest to feel working with a traditional crunch.

Unlike an exercise with external load, the challenge here scales with your own body's leverage: bent knees to lower the demand, straight legs to raise it, and hanging from a bar to push it further still. That built-in progression, without needing a plate or a machine, makes it one of the easiest ab exercises to scale at any stage of training.

Training pelvic control against the resistance of your legs' own weight also matters beyond looks: that same skill, keeping the lower back stable while the hips move, is what protects the lower back during heavy lifts like the squat or the deadlift, where a pelvis that moves too much under load is one of the most common causes of lower-back pain.

How to do it

  1. Lie on your back on the floor or a bench, legs fully extended, arms at your sides or hands tucked under your hips.
  2. Brace your abs and press your lower back into the floor before you move your legs at all: that's the starting position, not an optional detail.
  3. Raise your legs together, straight, toward the ceiling, without letting your lower back lift off the floor at any point in the range.
  4. Only go up as far as you can hold your lower back flat; if it starts arching before you get to the top, that's where your useful range ends.
  5. Pause briefly at the top with your abs still braced, without using momentum to reach higher than your core can actually control.
  6. Lower your legs under control to just short of the point where your lower back would lift off, not all the way to the floor.
  7. Repeat without letting your hips rock or your breathing stop; exhale as you raise, inhale as you lower.

Watch the video

Muscles worked

The prime mover is the rectus abdominis, especially its lower portion, which activates harder here than in exercises that flex the torso toward the legs, like the crunch. The real work, though, isn't lifting the legs: it's the posterior pelvic tilt that keeps the lower back flat on the floor while the hips flex.

The psoas and rectus femoris, as hip flexors, come in as unavoidable secondary movers; they're what actually moves the leg, but when they take over too much, that's the sign the abs have stopped holding the pelvis and the lower back has started arching. The obliques help as stabilizers, anchoring the pelvis against rotation as both legs rise together.

As additional stabilizers, the spinal erectors work isometrically to hold the lower back in a neutral position against the resistance the legs generate, and in the hanging version, the forearm flexors and lats join in, holding the grip and the entire suspended body through the whole movement.

Common mistakes

Floor or hanging

Floor or hanging from a bar is the real decision behind leg raises, more than just picking any variation.

The floor version, the one on this page, doesn't demand any grip or lat strength: the only limit is how much abdominal control the person has to hold the pelvis while the legs rise. That makes it the natural entry point, and it also lets you dial in difficulty precisely by bending the knees more or less, something that's much harder to fine-tune in the air.

Hanging from a bar, the whole body hangs from the grip, so on top of the abs, the forearms and lats come into play as support, and the floor stops existing as a limit: the lower back can arch more without any warning except the lifter's own attention. It's a considerably harder version, not just because of the range, but because it removes the point of support the floor version offers for free.

The practical call: start on the floor, knees bent if needed, and only move to hanging once the floor version with straight legs and no hand support under the hips stops being demanding enough. Jumping straight to the bar before that usually ends with a lower back that arches without the person noticing, exactly the error this exercise is meant to fix.

Frequently asked questions

Why does my lower back arch when I raise my legs?

Because the weight of the extended legs creates torque that pulls the pelvis forward, and if the abs don't counter it with a posterior pelvic tilt, the lower back lifts off the floor to compensate. When that happens, the psoas, a hip flexor, ends up doing the work instead of the rectus abdominis, the muscle this exercise is meant to train. The fix isn't forcing the full range: it's shortening it or bending the knees until the abs can hold the lower back flat through the whole movement.

Should my hands go under my hips or out to my sides?

Under the hips is a valid aid for a beginner: it gives extra support that makes it easier to keep the lower back flat while the abs don't yet have the strength to do it alone. As the exercise gets more manageable, pulling the arms out from under and placing them at your sides or crossed over your chest removes that support and demands more from the core directly.

Why are straight legs harder than bent knees?

Because straightening the leg lengthens the lever arm between the hip and the weight being moved, which increases the torque on the lower back for the same height of lift. Bending the knees shortens that lever arm and lowers the demand on the abs and lower back, so it's the simplest regression when the full range with straight legs makes the back arch.

When should I move up to hanging leg raises?

Once the floor version stops being demanding enough even with straight legs and no hand support under the hips. Hanging, the whole body hangs from the grip and there's no floor to limit how much the lower back can arch without it showing, so core control depends entirely on the person, not the surface. It's a harder progression, not a different exercise: the cue to keep the pelvis in a posterior tilt stays exactly the same.

Similar exercises

Abs trained through hip flexion don't cover every angle the core needs, and that's where the side plank comes in as a direct complement: it trains the obliques isometrically, resisting a lateral force that leg raises, a sagittal-plane movement, never touch at all. Together, they cover hip flexion and resistance to lateral trunk flexion, two of the most common patterns a well-trained core needs to hold up outside the gym.

Programming both in the same core routine doesn't compete for the same stimulus: one trains dynamic pelvic control under the weight of the legs, the other trains static trunk stability under its own bodyweight, so they add up instead of repeating each other.