Flutter Kicks
Flutter kicks have you lying on your back, legs lifted a few inches off the floor, alternating small up-and-down kicks while your lower back stays pinned down. It's a lower-ab endurance move: nothing about it looks impressive, but held with good form it makes your deep core muscles work continuously for the length of the set. It suits anyone building basic ab endurance and works as a quick finisher after other core exercises.
Why it works
Lifting straight legs even a few inches creates a long lever that tries to pull your lower back into an arch, and your deep abdominals have to fight that pull the entire time to keep your spine neutral. Because the kicks are small and continuous rather than one big rep, the muscles don't get a rest between reps the way they do in a slower exercise, which is what turns this into an endurance challenge rather than a strength one. The lower your legs hover, the harder that fight becomes, so height above the floor is really your intensity dial.
Set up
- Lie on your back on a mat with your legs straight and together.
- Rest your hands under your glutes or flat on the floor beside you, whichever helps your lower back stay down.
- Lift both legs a few inches off the floor and press your lower back gently into the mat.
How to do it
- Kick one leg slightly upward while the other drops slightly lower, staying just above the floor.
- Keep both legs straight with a soft bend in the knees, not locked stiff.
- Alternate the kick quickly but in a small, controlled range.
- Keep your lower back pressed down the entire time; if it lifts, raise your legs a little higher.
- Continue the alternating kicks for the length of the set.
- Lower both legs to the floor to finish, resting before the next set.
Form cues
- Small, quick kicks, not big swings.
- Lower back glued to the floor.
- Legs stay long, knees soft.
- Breathe steadily, don't hold it.
Breathing: Keep breathing in a steady rhythm throughout the set; holding your breath tends to let the lower back arch.
Common mistakes
The lower back arches off the floor as fatigue sets in.
Fix: Raise your legs a bit higher off the floor and shorten the set; a smaller, back-flat range trains more than a bigger one that lets the spine sag.
Kicking with big, wide swings instead of small flutters.
Fix: Shrink the range to a few inches; the exercise is about continuous tension, not distance traveled.
Holding the breath through the whole set.
Fix: Breathe in a steady rhythm; a held breath is usually a sign the range is too demanding right now.
Chasing a long time cap while form falls apart in the second half.
Fix: Cut the set the moment the lower back lifts, rather than finishing a fixed time with bad form.
How to program it
- Start with 2 or 3 sets of 20 to 30 seconds, keeping the lower back flat for the whole duration.
- It works well as a finisher after other ab work like the dead bug or plank, when the lower abs are already warm.
- Progress by raising the difficulty, holding the legs a touch lower, before chasing longer time.
- Two or three sessions a week is plenty; this muscle group doesn't need daily training to improve.
Safety notes
- If your lower back arches no matter how high you raise your legs, stop and switch to the dead bug until your core control improves.
- Keep the kicks small; a wide, forceful kick can strain the hip flexors more than it works the abs.
Exercise profile
- Force
- Pull
- Mechanics
- Compound
- Category
- Strength
Frequently asked questions
How long should I hold flutter kicks?
Twenty to thirty seconds per set, for 2 or 3 sets, is a solid starting point. Stop the moment your lower back lifts off the floor rather than pushing to a fixed time.
Why does my lower back hurt during flutter kicks?
Almost always the legs are too low or held there too long for your current core strength. Raise your legs higher off the floor, shorten the set, and build up gradually.
Flutter kicks vs leg raises: which is better for abs?
Leg raises move through a bigger range and challenge strength more; flutter kicks keep a small range and challenge endurance. Many programs use leg raises to build capacity and flutter kicks as a finisher once that capacity exists.
Do flutter kicks work the hip flexors more than the abs?
Both are involved, since lifted straight legs recruit the hip flexors by nature. Keeping your lower back pressed down and the kicks small keeps the emphasis on the deep abdominals rather than letting the hip flexors take over.