If you're interested in reading more on ideas presented in the article below, I suggest reading Don't Just Sit There. If you'd like movement instruction via video, start with Alignment Snacks: Hips Don't Lie, They Sit.
The other day I walked into my sister’s living room and found my niece in a “W” sit.
“Hey,” I said, “Do you see how your legs are making a “W” shape?”
She said, “No they’re not.”
I said, “Yes, they are, see?” And I traced out the letter with my hand.
She said, “That’s an “M”.
And she said, “Wow, for someone who teaches the importance of perspective, you’re pretty poor at it.”
Then I hit her and ran out of the room crying.
Anyhow, it seems that the “W” sit has been named in a way that makes it meaningless (or at least confusing) to the person doing it, while making total sense to the person “in charge of fixing it.”
To avoid scenes like this in the future, I’m going to start calling this way of sitting by what it is anatomically: excessive internal rotation of the thigh bone coupled with excessive external rotation of the lower leg bones, that when done repeatedly during the course of development will lead to compromised orthopaedic outcomes.
A.k.a, the EIRTTBCWEEROTLLBTWDRDTCOFWLTCOO sit.
Be honest. Who just checked my acronym? Anyone? Anyone?
Many children develop this sitting posture due to a lack of age-appropriate core strength -- often a result of the pelvic tucking posture promoted in almost every baby-apparatus that exists on the planet. A child without enough core muscle to actively stabilize the spine will need additional upright support. The shortened psoas (from the tucked pelvis) coupled with the legs out to the side increase spinal stability without using core muscles.
You with me?
In addition to the outward legs, there will also tend to be a tucked pelvis and rounded upper spine, which is why you can't just have them adjust their legs to this:
(or with their legs straight out or crossed-legged in front or one leg straight and one bent or...), you also have to address the root issue -- the tucked pelvis -- with a folded towel, small blanket, or pillow:
Which you probably have lying around all over the place because you no longer have furniture.
Am I saying that parents should now go screaming into the room telling your kid that it's BAD to sit "like that"? Yes. Absolutely. Because that works and will not leave any future stories about "how my parents were always correcting me because I wasn't good enough."
I suggest that the entire family sit on the floor together, exploring the way they like to sit, which way is more challenging -- taking turns being impressed with everything everyone elses's body can do, and then introduce a norm of using props to sit in a new way.
And, your house looks like this too, right? Especially 45 minutes after cleaning it??
Look for more "the cousins are here and Aunt Katy is making everyone work on their alignment" posts next week.