Dr. Stacy Sims

So we look at stress and the mom under stress. We see that there's a higher incidence of a miscarriage if it's a developing boy fetus than a girl fetus. And it has to do with XX versus XY. Okay. Then after birth, we see that there's relatively little sex difference that is apparent until the onset of puberty.

But when we're looking at those sex differences that aren't that apparent, there are there. We see that there's a sex difference in what we call muscle morphology. So that means that men are born with more fast twitch fibers. So they have more anaerobic capacity as they get older. They have more ability to produce power. We see that girls are born with more endurant type fibers.

But when we're looking at those sex differences that aren't that apparent, there are there. We see that there's a sex difference in what we call muscle morphology. So that means that men are born with more fast twitch fibers. So they have more anaerobic capacity as they get older. They have more ability to produce power. We see that girls are born with more endurant type fibers.

So this means they have more mitochondria for oxygen consumption and oxidative stress and being able to go long and slow. Then when we get to the onset of puberty, we see an expansion of these sex differences with the exposure of the sex hormones. So what we're seeing is now the boys are getting leaner, they're getting faster, they're getting more aggressive.

So this means they have more mitochondria for oxygen consumption and oxidative stress and being able to go long and slow. Then when we get to the onset of puberty, we see an expansion of these sex differences with the exposure of the sex hormones. So what we're seeing is now the boys are getting leaner, they're getting faster, they're getting more aggressive.

But girls' bodies completely change because center of gravity drops from the chest down to the lower abdomen area because their hips widen. And their hips widen because, you know, being XX, they have to then accommodate for getting pregnant and eventually having a baby from a biological standpoint. Hips widen, shoulders widen. This changes the angle of the knee to the hip. So we then have a, yep.

But girls' bodies completely change because center of gravity drops from the chest down to the lower abdomen area because their hips widen. And their hips widen because, you know, being XX, they have to then accommodate for getting pregnant and eventually having a baby from a biological standpoint. Hips widen, shoulders widen. This changes the angle of the knee to the hip. So we then have a, yep.

The Q angle, yes.

The Q angle, yes.

Yep.

Yep.

Yeah, yeah. And so when we're looking at girls whose bodies are changing, we see that by the age of 14, girls who previously were sporty, over 60% of them drop out of sport. Because they're not taught that their bodies are changing, so they don't feel comfortable running or swimming or jumping or landing. Because they have a new cue angle, they become quad dominant.

Yeah, yeah. And so when we're looking at girls whose bodies are changing, we see that by the age of 14, girls who previously were sporty, over 60% of them drop out of sport. Because they're not taught that their bodies are changing, so they don't feel comfortable running or swimming or jumping or landing. Because they have a new cue angle, they become quad dominant.

Their center of gravity is different. Their shoulders are wider, so they don't feel comfortable running because their whole running mechanics change. So, you know, when we're looking at girls who are eight, they can keep up with the boys, right? Their bodies haven't quite started changing yet. By the time they're 10... They're starting to see a discrepancy.

Their center of gravity is different. Their shoulders are wider, so they don't feel comfortable running because their whole running mechanics change. So, you know, when we're looking at girls who are eight, they can keep up with the boys, right? Their bodies haven't quite started changing yet. By the time they're 10... They're starting to see a discrepancy.

And I say that because my daughter's now 12, and I've seen it over the course of the elementary school years where they used to be on par with the boys playing soccer and rugby and stuff on the field. And then you start seeing a morph where the boys are... becoming more aggressive and they're kicking the balls faster and running faster.

And I say that because my daughter's now 12, and I've seen it over the course of the elementary school years where they used to be on par with the boys playing soccer and rugby and stuff on the field. And then you start seeing a morph where the boys are... becoming more aggressive and they're kicking the balls faster and running faster.

And the girls are starting to develop a little bit more, getting a little bit more body fat, feeling a little bit more comfortable running. They can't do the monkey bars anymore because their center of gravity is lower, so they can't get up and do the monkey bars as well. But no one explains this to them.

And the girls are starting to develop a little bit more, getting a little bit more body fat, feeling a little bit more comfortable running. They can't do the monkey bars anymore because their center of gravity is lower, so they can't get up and do the monkey bars as well. But no one explains this to them.

So then when we see this discrepancy of being sporty, not sporty, we see the changes in body composition. And all of this is in those early stages of the teen years, which is another knock because we also have brain changes where girls become more self-aware and boys don't. They're like, okay, you know what? You piss me off. I'm going to beat you up and we're going to get on with it.