In any sport, you move up to the next level step by step.
In swimming, once you can put your face in the water, the next step is streamlining.
Once you are able to float, the next step is flutter kick.
Flutter kick! That’s the basics of swimming.
You might practiced flutter kick by sitting on the side of the pool, then grabbed a kickboard and practiced in the pool, didn’t you?
For flutter kicks, it is told, “Do not bend too much at the knees” or “Use your legs flexibly”.
Or, “Drive your kicks from the hips”.
But wait a minute.
Isn’t that kind of hard to understand?
I’ve come to one truth.
Flutter kick doesn’t have to kick.
Don’t kick, twist!
Let me explain about that.
Where is the root of the leg?
First, let’s talk about anatomy.
Where is the root of the leg?
“Hip joint!”
Exactly right.
“Thigh bone” fit into “pelvis”. That makes “hip joint”.
To be precise, “femoral head” fit into “acetabulum”.
So, we can say that the root of the leg is the hip joint. Isn’t it?
In terms of frame, that’s the right answer.
Let’s look at it from another perspective.
Where are the muscles that move the legs attached?
Thigh and pelvis.
But this is not all.
There is a super strong muscle that pulls the legs up, the iliopsoas muscle.
And the iliopsoas muscle connects the femur to the lumbar spine.
(The psoas minor and psoas major muscles connect the femur to the lumbar spine, and the iliopsoas muscle connects the femur to the pelvis, so the femur, pelvis, and lumbar spine to be exact.)
In other words, the muscles that move the legs extend beyond the hip joint to the lumbar spine.
This means that the main origin of leg movement is deep in the abdomen in terms of muscles.
If you want to replace it with an easily recognizable landmark, the navel.
That is to say, in terms of muscles, the root of the leg is the navel.
Therefore, it is more correct to understand that we should kick with the navel, not with the hip joint.
As with running, the propulsive force of the kick is more efficiently generated by the iliopsoas muscles than by the thighs.
But kicking at the navel doesn’t make sense, does it?
This is where the opening word comes into play.
Don’t kick, twist.
“Twist” with the lumbar spine and iliopsoas muscle
Look at this picture once again.
The left and right iliopsoas muscles are combined into one at the center of the body: the lumbar spine.
Twist your lower body around this lumbar spine.
The image of a compass as an analogy.
Instead of thinking of the legs as separate left and right sides, think of them as a single cohesive unit, starting from the lumbar spine.
Instead of fluttering the two bars(=legs), twist them around the axis as a fulcrum.
It’s not a parallel motion up and down, it’s a rotational motion, the flutter kick is.
If you rotate the lumbar spine on its axis, both legs will sway in response to each other.
Imagine twisting the upper and lower body with the navel as the fulcrum.
It’s like “twist dance” motion.
Moving effortlessly, twist-flutter kick practice
Practice sitting on a chair
Let’s practice sitting on a chair.
Let’s start with a normal flutter kick.
Sitting shallow, legs floating, both legs flapping alternately.
You’re working hard with your thigh muscles.
Next, try floating your legs and rocking your shoulders.
It’s like “twist dance” motion.
Don’t you feel your legs flap in tandem with shoulders?
With the navel as the fulcrum, the upper and lower body twist in opposite directions.
And just look at the legs, it is exactly the same as the “normal flutter kick” motion!
At this moment, are your thighs straining?
You will surely notice that your legs are naturally relaxed.
“Navel flutter kick” relaxing your legs naturally
The normal flutter kick makes you feel like your legs are working hard, but the navel flutter kick is easy on the legs.
Here’s one more important point.
When you will do a normal flutter kick, you will try to control the bending and extending of your knees.
However, the “navel flutter kick” even controls the knees by itself without thinking about it!
You don’t have to think about “bending and extending” your knees anymore
By bringing your awareness to the navel instead of your legs, your legs will relax on their own.
And because of the whip-like snap from the navel, the ideal leg kick with relaxed knees and ankles is achieved on its own!
If you try to kick intentionally, your knees tend to bend too much.
The ideal kick is made by daring not to kick.
Flutter kick practice in the pool
Practice in the actual pool using a kickboard. (Without a kickboard if you can)
The conventional wisdom is that “flutter kick” = “a reciprocating movement” of the right and left legs up and down respectively, with the pelvis fixed.
Implement “navel flutter kick” and feel the difference in sensation!
When first practicing “navel flutter kick”, do not focus on the navel at first, but rather twist your entire body from side to side with your head as your axis.
The image of a wave of swaying throughout the body that is eventually replaced by propulsion in the legs.
Once you get a feel for it, fix your upper body and twist only from the navel down.
Additional tips
The larger the area of water captured by the instep, the greater the propulsive force.
Just as you can catch more water by rowing with wide oars than with narrow oars.
The toes should be slightly inward rather than straight, to allow for a wider foot width.
Best to have thumbs touching each other.
Lastly
You may have thought, “I’m kicking so hard , but why am I making so little moving forward?”
You’re probably tempted to try it out in the pool right away, aren’t you?
By not kicking with your thighs, you will find it surprisingly easy to flop and move forward smoothly.
“What was all that hard work until now?”
Learn to flutter kick without getting tired.
And, please enjoy swimming!
