The Missing m(Ass)

Only about 5 times a week do people send me this infographic on pregnancy and posture and ask me what I think.

First of all, you shouldn’t care what I think. You should care what you think. But, I also realize that what you are really asking is for more information to interpret this advice for yourself. So that’s what I’m going to give you.

1. When you are standing, the body’s center of mass lands in the pelvis.

2. In order for the mechanoreceptors of bone (as well as those in the uterus, pregnant or not!) to work appropriately, the body needs to be vertically stacked, which means keeping the pelvis neutral, on a vertical leg, over the ankle, blah blah blah you’ve heard me say this a bunch of times.

3. Clearly, when pregnant, you will accumulate the additional mass of the baby, some of which will end out (way) in front of you. Clearly.

Which means that now the center of mass of your body is forward to where it used to be.

Which is why it would make sense (at least to the creator of the graphic) that you should perhaps, slightly bend your knees and tuck your pelvis underneath, bringing your skeleton toward your *new* center of mass that is out in front of where your old one once was (see infographic).

I just wanted to point out that the premise everyone has agreed upon to this point is that being pregnant dictates that your center of mass has moved forward. But here’s the thing. This “your center of mass is now forward” model you are subscribing to is the modern-living, unmoving or moving in unnatural ways, pregnant-in-a-vacuum (or at least in a chair) one. So the solution isn’t really addressing the real problem (the missing mASS) and is a band-aid fix. A band-aid fix that leaves you with a few other health issues.


We cannot deny that there is more mass now on the front. And we cannot deny that it needs to be supported. The question is, does dragging the entire skeleton (and organ systems) out of alignment during the time when one of the most biologically normal processes is about to go down make sense? Do you think that nature intended for pregnancy to be a period of time when the spine and the pelvis needed to bend and contort to support itself?

Of course not.

So, picture this. You’re getting heavier every day but you’re walking around with this extra mass. A lot of walking like 3-10 miles every day. And you’re going up and down hills (not just walking a track) and you’re carrying stuff. And squatting to pee. And more importantly, getting out of the squat (groan) when you’re done. And also getting up and down off the ground a bunch of times. What happens, little exercise scientists? You’re getting stronger, right? Which means that you’re increasing the mass of your muscles — specifically those that propel you forward, which, if you’re walking around without heeled shoes and you don’t have quads and psoai of steel, means you’re using your butt, hamstrings, and calves more.

And if we add this backside:

to this body:

We get a center of mass

that is exactly where it was before this whole party started.

Not fully understanding 1) mass,  2) our ability to respond and adapt to mass (especially nature’s intended mass accumulation) and 3) natural movement’s role in keeping the body biologically optimal can leave you with a logical solution — see infographic — that is biologically non-optimal.

So you ask what I think of recommendations that have us distort our skeletons to mitigate the “natural center of mass changes brought on by pregnancy?”

I think that whoever made these recommendations has only thought through a very small part of the equation (the extra mass in front) and didn’t consider that in less modern times, natural movement quantities and qualities would have made this a non-issue (more junk in the trunk, hamstrings, and calves).

They are also failing to considering that:
1. Slightly flexing your knees tenses your quads and increases pressure and friction under the knee cap.
2. Slightly tucking the pelvis causes excessive pressure on the sacrum (ow) during sitting and minimizes gluteal contraction (and therefore development) while walking. It also increases tension in the pelvic floor — not good for vaginal delivery.
3. Tilting the pelvis also tilts the uterus, changing the interaction between baby and uterus, and the uterus and the brain — not optimal for fetal movements and cervical dilation as well as other important uterine functions like menstruation, fertility, etc.

I’m also not going to mention that if you didn’t rib thrust all of the time, more of the baby’s mass would be over your pelvis instead of out in front of you. I also won’t mention that if you didn’t rib thrust all of the time, your transverse abdominals would produce a much greater force in supporting the uterus to that your skin and connective tissue between the linea alba and rectus abdominals wouldn’t have to hold it for you.

But what I think shouldn’t be important. What matters is what YOU think, and why. And why, and why, and why.

That was a rhetorical question.

Are you still interested in learning more on this?

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29 thoughts on “The Missing m(Ass)

  1. very helpful info., will share with younger, childbearing age friends, including my daughter. no rush for her 🙂

  2. Thank you! I’m currently 24 weeks, and while I knew that I shouldn’t have to tilt my pelvis (which was a lifelong habit even before this third pregnancy) I couldn’t help but wonder about the center of mass, but this makes so much sense! Clearly I have to start walking more, squatting more, getting up and down off the ground more, etc. etc. etc. The vicious cycle of not doing those things because I’m achy and sore and cumbersome will only get worse because the less I do them, the achier I get.

  3. How would you say, Katy, in your metaphor of balance, does allowing a bit of lordosis into play fit into this…
    Or is that the pelvic tilt you are talking about?

    I’m glad to see no butt tucking, thank you!

    I’m so enjoying your enewsletters!

    1. Well, unclear on what “metaphor of balance” means? There is a structural distribution of mass that stabilizes the body. If you click on the graphic, you can see the oft-recommended “soften the knees” which, of course, also results in a slight flexion of the hips and often a slight tuck to the pelvis. The lumbar curve should absolutely remain in tact, for if not, the TVA are no able to support the weight of the growing baby (or assist the uterus when it’s time). Neutral is pretty specific and not “open to interpretation” if you read through the “neutral pelvis” post and add the position of the ribs — you will find the correct amount of curve for your (or your clients) body!

    2. Also, “butt tucking” is “pelvis tucking” which always gets you lumbar flexion — an often missed reality. Then, that “lordosis” has to be recreated by shearing the rib cage, making it not lordosis at all, if that makes sense…

  4. Wonderful explanation! Thx. When I work with pregnant women–ok, actually when I work with anyone female, male, pregnant, not–I talk about a vector of support. Placing one hand well below the client’s navel and the other hand on the client’s upper back I invite them to think about “the baby” flowing back & up. Voila! The New Anatomy!!

    Actually…the baby doesn’t go anywhere near the upper back. Not even in pregnant women. But the concept allows for moment-by-moment, day-by-day adjustments to the effects of the growing fetus. And in those folks who aren’t pregnant it gives them a new experience of how the entire Structural Body balances more accurately upon the structures of the legs.

    My favorite pregnant woman-story is about a woman who was less than 5′ tall and who’d gained at least 20#. Even at the very end of her pregnancy she walked as if she were merely floating. No ‘waddling’ [aaack] No tucked or over-arched pelvis. No collapse of her upper torso and neck.

    Besides which…baby made it to the outside relatively easily, all things considered. Come to think of it, so has each baby belonging to a pregnant mom who’d worked even a short time with me! What do you think, Katy: what is there about this structural rebalancing which allows the process of labor and delivering to be easier???

    1. Lynn, You must be new to the blog? Take a read through the last few years of posts — a good place to start getting the gist 🙂

  5. I’m 26 weeks pregnant with my third boy, so I’m enjoying your pregnancy posts. I’m still waiting for the one about a miracle cure for varicose veins 🙂

    Anyway, I’ll probably get in trouble for asking this, but what effect do pregnancy support belts have on the body? I have friends who swear by them for comfort or minimizing diastasis recti, so the bigger I get, the more tempted I am to purchase one. I do a fair amount of walking hills, squatting and running after little people, but this belly is getting heavy! Thanks!

    1. I could be wrong, but I seem to remember reading somewhere among Katy’s writings that varicose veins are due to reduced blood flow caused by improper alignment. I know my left leg which is the one with varicose veins tends to ache when I’m haven’t been consciously standing correctly.

      Also, I seem to remember seeing a couple of posts on different pregnancy/post-partum belts on Katy’s Facebook page in the last month or so.

  6. I have to admit, I was pretty proud of my non-waddling, “don’t look pregnant from behind” self with DD and now, again, at 24 weeks. This time, with Katy’s virtual encouragement, it is vibrams instead of any positive heels (fo’ sho’)… my calves and hams are rockin’ 😉 Thank you Katy!

  7. After the birth and the stronger butt and legs have done their work, do these muscles then gradually re-adjust and go back to where they were before, assuming that they are not now needed to be as strong? Or am I getting very confused about muscle strength and muscle bulk? Or maybe they are actually still needed as you’re now required to continue to carry around the bundle of joy until it can walk by itself? That would make sense…I think…I am always worried that I ask a silly question…!

    1. Never be afraid of asking and this isn’t a silly questin at all!

      Well if we were more baby carriers, then there would still be a need for strength, some of it in the legs, but I’d imagine (and have experienced) that the muscle subsides in the legs and moves to where carrying something higher and in arms is needed. You’re also just carrying it (the weight) less (and, it’s a lot lighter — the baby, compared to the pregnancy mass) so there’s not the same mechanical/physiological stuff going on. Also, as glorified as the BULK in the drawing is, it’s not that much actually as most baby mass should be still pretty much vertically stacked 🙂

  8. Do you have any photos of you before and now pregnant from the side, so we could see what the new (leg/butt) proportions look like? Or just a pregnant one as there are quite a few of you being non-pregnant and in alignment?

    1. Yes! I have them. I’ll see if I can work them into a post — working on a DR post as well as a BONE LOSS during pregnancy post. Although my mass accumulation will have little to do with what someone’s should look like. The biological standard of necessary fat and fat-free mass is well-calculated. And the amount of that out in front is very little (I believe I mentioned about 2-6 pounds max somewhere in the comments) so to try to “see” what 2-6 pounds looks like on someone who is long-legged and 5′ 7″ would look entirely different than someone who developed musculature in response to moving their new load who was 5’2 and short legged. You can also check out my back fat — another standard place for weight accumulation in pregnancy that is more biological in nature and has less to do with the inactivity and modern diet…

  9. RE: support belts. A friend of mine mentioned that a one piece competition bathing suit worked well for pregnant belly support. Buy the size you would wear when not pregnant and see how it works.

  10. This is awesome and makes so much sense. I wish I’d known this a year ago when I was pregnant with my first. I’m afraid I was a terrible waddler! But I’m doing all that I can to prevent that happening next time around.

    Thank you so, so much for your blog. I think I’m almost done reading the entire thing and I’m typing from the new standing work station we set up. I’ve been doing lots of stretching (easy to fit in at home) but I know I need to get out walking more. Last night I finally figured out why my husband was having trouble backing up over his heels – tucked pelvis caused by super super tight hamstrings caused by hypermobility. (It was confusing at first because he could touch his toes/put his palms on the ground with no problem, but then we realised he was bending from his back and not his hips.) He’s now on an Rxercise prescription of 2 mins hamstring stretch every hour!

    We love your blog and dvds and are learning so much. Thank you!

    Ps. I think my favourite ever blog post is your Dear Henry one. Had me laughing out loud!

  11. Thanks for your reply to my question above;-). I am interested that you say that muscle ‘subsides’. Is it a misconception that muscle ‘turns to fat’ as some people say? Is it that muscle is a different type of tissue and cannot change into a fatty deposit type of tissue?? That makes sense in my head but could be totally wrong!

    1. Unused muscle mass will result in destroyed proteins. No, it does not turn into another tissue (sounds magical though!) When you don’t use muscle tissue, signals for decrease in production and increase in destruction ensue — the cells break it down and get it outtathere (the “outtathere” is complicated and over my head — wish I knew more biochemistry!) I think the “turns to fat” thing must have been based on the ration of fat to lean mass. As you lose lean mass, it would increase the ratio (but not the total amount) of fat mass to lean mass. Perhaps someone got confused on the math part…

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