Floor Leg Raises

What floor leg raises actually train

A floor leg raise is a bodyweight core exercise in which you lie on your back and raise both straight legs to vertical, then lower them until they hover just above the ground.

The muscles that lift your legs are not your abdominals. Hip flexion is produced by iliopsoas, rectus femoris and the smaller hip flexors, and they are the prime movers throughout. Your rectus abdominis and obliques contribute nothing to raising the leg itself.

What they do instead is more interesting. The psoas attaches to the lumbar vertebrae, so when it pulls your legs up it also pulls your lower spine into an arch. The abdominal wall has to resist that, hard, for every second the legs are off the floor. That is an isometric anti extension contraction, and it is the reason a set of leg raises burns where it does.

Understanding this changes how you do the exercise. The abdominal work is not in raising the legs; it is in keeping the lower back flat while they are down near the floor. The lower your legs travel, the longer the lever and the more the abs have to resist. The top half of the rep is close to a rest.

Escamilla and colleagues compared abdominal exercises using electromyography and found that leg raise style movements produce substantial abdominal activity alongside considerable hip flexor involvement, which fits exactly this picture.

None of that makes the exercise bad. Hip flexor strength is genuinely useful and undertrained, and an anti extension contraction under a long lever is a legitimate way to train the abdominal wall. It just means you should judge the set by whether your back stayed down, not by how far your legs went.

Setting up and executing

Lie on your back with the legs straight and together. Put your hands flat beside your hips, or slide them under your tailbone if your back struggles to stay flat.

Press the lower back firmly into the floor and brace the abdominal wall as if you were expecting a light punch. Do this before the first rep.

Set a small fixed bend in the knees. Fully locked knees make the lever longer than most people can hold.

Raise both legs until they are roughly vertical, keeping the pelvis still rather than curling it up off the floor.

Lower the legs slowly over three seconds, and stop the moment your lower back begins to lift. Pause just above the floor without touching down, then raise again.

The mistakes that cost you the most

Letting the lower back arch is the only mistake that really matters, because it converts the exercise into something else. Once the lumbar spine lifts, the abs have given up and the psoas is pulling directly on your vertebrae with your legs as the lever. If you feel this in your lower back rather than your stomach, that is what is happening.

Going lower than you can control is the usual cause. Your working range is defined by where your back stays flat, and for many people that is a good deal higher than the floor. Shorten the range and the exercise starts working immediately.

Resting the legs on the floor between reps releases the tension at the hardest position and turns one hard set into ten easy singles.

Swinging the legs up removes the abdominal demand from the raise and hands the whole movement to the hip flexors.

And locking the knees hard is a vanity detail. A small bend shortens the lever slightly and lets you control a longer range, which is a better trade than straight legs and an arched back.

Sets, reps and rest by goal

Treat this as accessory work and keep the reps moderate to high.

For muscle gain, three sets of ten to twenty with a minute rest. For strength, three sets of eight to fifteen with ninety seconds. In a fat loss phase, three sets of fifteen to twenty five with forty five seconds.

The variable that should progress is range, not reps. Start by lowering to forty five degrees with the back flat, and over weeks work towards the floor. Adding reps to a range you cannot control is progress in the wrong direction.

Slow the lowering to three seconds. Almost all of the useful work happens on the way down, and rushing it removes most of the exercise.

Schoenfeld and colleagues found a dose response between weekly hard sets and hypertrophy, so if visible abdominal development is the goal, a few honest sets twice a week beat one long session of high rep work.

Refalo and colleagues found training close to failure and stopping short produce comparable hypertrophy. On this exercise the natural stopping point arrives when your back lifts, which is usually earlier than muscular failure and is the correct place to stop anyway.

Where it fits in your split

At the end of a session, in the last five minutes.

On push, pull and legs it fits on legs day or gets added to whichever session has time. On a bro split it goes last on leg or shoulder day. On an upper and lower split it works well in the full body session after the main lifts. On a full body programme it is a fast finisher that needs no equipment. On a bodyweight programme it is your main anti extension movement.

Do not put it before squatting or deadlifting. Pre fatiguing the abdominal wall and the hip flexors makes bracing harder on the lifts that actually need it. Cholewicki and colleagues measured the very large spinal loads involved in lifting heavy weights, and the muscular stiffness that manages those loads is not something to spend beforehand on leg raises.

Twice a week is enough. The abdominal wall is not special; it responds to the same volumes and frequencies as everything else.

Variations worth knowing

The hanging leg raise is the same movement from a bar. It adds range at the top, removes the floor as a reference point and introduces a grip limit that often arrives first.

The lying knee raise keeps the knees bent throughout, which shortens the lever considerably and is the right starting point for most beginners.

Flutter kicks alternate the legs near the floor, holding you in the hardest position continuously rather than passing through it.

The reverse crunch curls the pelvis off the floor at the top, which genuinely shifts work from the hip flexors to the abdominals and is a better choice if abdominal work is the only aim.

The ab wheel rollout produces the same anti extension demand from the opposite end of the body, with more load and a longer lever.

And a banded lying leg raise adds resistance towards the top, where the movement is otherwise close to a rest.

What the evidence says

Escamilla and colleagues compared common abdominal exercises with electromyography and found leg raise style movements generate high abdominal activity, though with substantial hip flexor contribution alongside it.

A second analysis from Escamilla and colleagues covering traditional and nontraditional abdominal exercises reached similar conclusions, showing that exercises differ mainly in how they distribute work between the abdominal wall and the hip flexors rather than in whether they train the abs at all.

Marchetti and colleagues studied muscle activation during isometric ab wheel rollouts in different shoulder positions and found high abdominal demand in the extended positions, which is the same anti extension principle that makes the bottom of a leg raise hard.

McGill's work on core training argues that the abdominal wall functions mainly to resist unwanted spinal motion rather than to produce it, which is the clearest justification for judging this exercise by whether your back stays flat.

Cholewicki and colleagues measured lumbar spine loads during heavy lifting and documented how large they become, which is the practical reason not to fatigue your bracing muscles before heavy compound work.

Schoenfeld and colleagues found a dose response between weekly hard sets and hypertrophy, which applies to the abdominal wall as much as anywhere else.

Refalo and colleagues found comparable hypertrophy from training to failure and stopping a rep or two short, which suits an exercise where technique breaks before the muscle does.

Common questions

Why do I feel this in my lower back?

Because your lumbar spine is arching off the floor and the hip flexors are pulling on it directly. Raise your stopping point until your back stays flat through every rep, and put your hands under your tailbone if that helps. The range will extend over a few weeks.

Is this an abs exercise or a hip flexor exercise?

Both, and the split is not fifty fifty. The hip flexors move your legs; the abdominal wall works isometrically to stop your spine arching while they do. If you want a movement that is more purely abdominal, use a reverse crunch.

Why is it filed under legs?

Because the movement itself is hip flexion, driven by muscles that cross the hip. The training effect you feel is mostly abdominal, which is why the target muscles list says what it does. The naming is about the joint, not the burn.

Should my legs be straight?

Slightly bent is better for most people. A small fixed bend shortens the lever enough to let you control a longer range with a flat back, which is a better exchange than locked knees and a compromised position.

How is this different from a hanging leg raise?

The floor gives you feedback and a hard limit; the bar gives you more range and a grip problem. The hanging version is harder and more complete, so use it if you can hold on long enough. This one is the version you can do anywhere.