Muscles worked
Flutter kicks are an endurance exercise for your trunk. Your hip flexors do the kicking, while your abs work statically for the whole set to keep your pelvis level and your back flat against the floor. Unlike the lying leg raise, there is no point where your legs feel light, so the tension lasts from the first second to the last. Your quads keep your legs straight. Lower legs mean more for your abs to resist.
Common mistakes
- Your heels touch the floor. Putting your feet down between kicks gives your abs a break each time. Keep both heels a little above the floor for the whole set.
- The kicks come from your knees. Bending your knees on each kick turns it into a swimming motion with your lower legs, and your hips do less. Keep your legs long and let the movement start at the hip.
- Your pelvis rocks from side to side. Quick kicks tend to drag your hips along. Press your lower back down evenly on both sides and shrink the kicks until your pelvis stays still.
Variations and alternatives
- Scissor kicks cross your legs sideways instead of up and down, for variety.
- The lying leg raise has a longer, slower movement and suits you when you would rather build strength than endurance.
- The dead bug is easier and teaches you to keep your lower back down one leg at a time.
Sets and reps
Flutter kicks are usually done for time. Two to four sets of 20 to 45 seconds suit most people, with the same rest or a little more. If you prefer counting, try 20 to 40 kicks per set, counting each leg separately. For matching the dose to your goal, see the guide to sets and reps.
Build up the time first, five seconds at a go. Then lower your legs nearer the floor, but only as far as your lower back stays down. Lifting your shoulder blades as well makes it considerably harder. That is progressive overload, one step at a time. If your lower back hurts, and it is not just your abs burning, stop and let a doctor or physiotherapist assess it.