The Flutter Kicks: A Complete Guide From First Rep to Advanced Variations
Also called Scissor Kicks, Flutter Leg Kicks
Quick Intro
Flutter kicks are a core exercise performed lying on the back, alternating small up and down kicks with straight legs held just above the floor.
Equipment Needed
Flutter kicks call for nothing beyond floor space and something soft under the lower back, like a mat.
Why Flutter Kicks Matter
Flutter kicks ask the lower portion of the abs (rectus abdominis) and the deep core muscle that wraps around the spine (transverse abdominis) to hold the lower back pressed into the floor while the hip flexors (iliopsoas) drive a continuous alternating kick. The core’s job here is almost entirely about resisting movement, keeping the pelvis and spine still, while the hip flexors handle the actual leg motion.
That combination is what makes this exercise demanding in a way that isn’t obvious from watching it. The legs look like they’re doing all the work, but if the core isn’t strong enough to keep the lower back glued to the floor, the hip flexors pull the pelvis and lower spine into an arch instead, which is both less effective at training the abs and harder on the lower back.
Flutter kicks are a muscular endurance exercise for the lower abs and hip flexors, with some muscular strength carryover from sustaining a continuous, unsupported kicking motion.
When to Do It
Flutter kicks fit well toward the end of a core-focused session, since the lower back needs to be warmed up and the abs primed before this exercise asks them to hold a static brace under continuous leg movement. Two to three sessions a week, with recovery between them, works well given how much the lower back is involved.
Existing lower back pain or a spine that tends to arch easily deserves attention here:
- Existing lower back pain or a lower back that tends to arch easily. If the lower back can’t stay flat against the floor through even a small kick, the exercise shifts load onto the spine instead of the abs. Shortening the kick range, bending the knees slightly or building up with a gentler core exercise first are reasonable adjustments.
For most people with a reasonably conditioned core already, this is an effective way to build lower ab and hip flexor endurance together.
Getting Ready
A minute of gentle knee-to-chest hugs and a few pelvic tilts warm up the lower back and core before asking them to hold a static brace through continuous kicking.
Press the lower back into the floor and keep it there for the entire set. A lower back that lifts off the floor at any point means the core has stopped doing its job and the spine has started compensating.
Step-by-Step Instructions
1. Starting position. Lie flat on the back, legs extended and straight, arms resting flat at the sides or tucked slightly under the lower back for support.
2. The kicks. Lift both legs a few inches off the floor and alternate small, quick up and down kicks, keeping the movement coming from the hips with the knees nearly straight.
3. The hold. Keep the lower back pressed flat into the floor throughout, continuing the alternating kicks for the full set.
Keep the kicks small, since larger kicks are the fastest way to lose contact between the lower back and the floor.
How Many, How Often
| Level | Where you’re at | What to do |
|---|---|---|
| Beginner | New to the movement | 2 to 3 sets of 15 to 20 seconds, keeping the legs slightly bent and the kicks small. Resting 30 to 45 seconds between sets. |
| Intermediate | 30 seconds come easily | 3 sets of 30 seconds, straightening the legs further and keeping the lower back flat throughout. |
| Advanced | 45 seconds or more come easily | Lower the legs closer to the floor, since a lower leg position increases the hip flexor and core demand without needing more time. |
Letting the lower back lift off the floor to kick faster is the easiest way to make the set look more intense while quietly shifting the load off the abs and onto the spine, so a flat, glued-down lower back matters more here than how fast the kicks move.
Modifications and Variations
Flutter kicks connect to one alternative.
As an alternative technique, Leg Raise lifts both legs together through a bigger range instead of alternating small kicks, trading the continuous endurance demand of flutter kicks for a slower, more controlled strength movement.
Bending the knees slightly to shorten the lever, or placing both hands flat under the lower back for extra support, are reasonable ways to reduce the demand while keeping the lower back flat.
Common Mistakes to Avoid
Letting the lower back arch off the floor. An arched lower back means the hip flexors are pulling on the spine instead of the core holding it steady, which is the exact opposite of what this exercise is meant to train. Keeping the lower back pressed down keeps the set honest.
Kicking with the legs too high off the floor. Raising the legs well above hip height shifts the demand away from the lower abs and reduces how hard the core has to work to stabilize. Keeping the legs low, just a few inches up, preserves the intended muscle emphasis.
Holding the breath through the set. Bracing hard and forgetting to breathe is a common response to a demanding hold, and it tires the core out faster than the movement itself should. Breathing in a steady, controlled rhythm keeps the set sustainable.
Letting the kicks get sloppy and uneven as fatigue sets in. Once the lower back starts to tire, the kicks often get bigger and less controlled without the person noticing. Stopping the set the moment the lower back can no longer stay flat keeps every rep meaningful.
After Your Set
The lower back tends to feel the effects of holding a flat brace for an extended set before the abs or hip flexors do. Lying flat and hugging both knees gently into the chest releases exactly that part of the lower back. A standing hip flexor stretch afterward, stepping one foot forward into a shallow lunge and gently pressing the back hip forward, lengthens the muscles that drove every kick.
Going Deeper
This exercise is a test of core endurance, which is why it tends to expose weaknesses that slower, more controlled core exercises can hide. Pairing it after a set of Dead Bug or Bird Dog, both of which build the same lower back control at a slower pace, gives the core a chance to apply that control under continuous movement.
The limit on this exercise is almost always lower back control, not hip flexor or ab fatigue in the traditional sense. Most people feel their hip flexors burning well before the lower back loses its flat position against the floor, but the moment that contact breaks, the exercise stops training what it’s meant to. Watching for that specific moment, not just counting seconds, is a better gauge of a set’s true length.
Someone with a reasonably conditioned core already can expect 20 clean seconds with the lower back staying flat within the first one to two weeks, reaching 30 to 45 seconds somewhere in the four to six week range.
How to Know You’re Improving
Sustained endurance here builds gradually from a brief, flat-backed hold, roughly on this schedule:
- 20 seconds with the lower back staying completely flat
- 30 seconds with the legs fully straightened and the kicks still small
- 45 seconds or more with no loss of position
- A comfortable set performed with the legs held closer to the floor
Whether the lower back stays flat for the entire set, not just the first few seconds, is the clearest sign this exercise is doing its job.
Muscles Worked
- Rectus Abdominis (the abdominal muscles running down the front of the stomach, holding the pelvis still as the legs alternate)
- Iliopsoas (the deep hip flexor at the front of the hip, lifting each leg in turn)
- Transverse Abdominis (a deep core muscle that wraps around the torso like a corset, holding the spine flat as the legs keep moving)
FAQ
Why does my lower back hurt during flutter kicks? That’s usually a sign the lower back has lifted off the floor and is bearing load it shouldn’t. Bending the knees slightly and shortening the kick range keeps the spine flat again.
What’s the difference between flutter kicks and a leg raise? Flutter kicks alternate small, continuous kicks for an extended hold, while Leg Raise lifts both legs together through a bigger range at a slower pace.
How low should my legs be during the kicks? A few inches off the floor is enough for most people. Lowering the legs further increases the difficulty and should only be attempted once the lower back stays flat at the easier height.
Is it normal for my hip flexors to burn more than my abs during this exercise? Yes, that’s common, since the hip flexors are doing the visible kicking work while the core’s job is the less obvious task of holding the spine still underneath it.
Next in this series: Squat to Stand, a hip and hamstring mobility drill that moves between a deep squat and a standing toe touch.