- So squeeze your butt for me.
- Oh, okay. Squeezing.
- There you go. - Cool!
- And then relax.
- Relaxing.
- Nice.
- This is really cool. This is, like, really cool.
- I know that you're watching Physics Girl
and now, maybe you know too.
Hi, I'm Diana and this is definitely not a fitness channel,
but Blogilates is, and it just so happens
to be the most popular pilates channel on YouTube
and Cassie from Blogilates got me to do a butt workout.
I love that you're able to talk while doing this, Cassidy,
because I'm starting to die.
- Good!
- That was way outside of my comfort zone,
but I took her afterwards to a lab and experimented on her.
So, hah!
- So we will place these electrodes on, right on the skin,
right above certain muscles that we want to see activate.
I'm going to put this electrode on your gluteus medius.
We'll hook them up to these cables
and into these wireless transmitter boxes.
And so we can get the electrical activity of the muscle sent
to the computer wirelessly and can look at when the muscles
are on and how much they're on, that sort of thing.
- I was really curious to see
which of your butt muscles light up
and which of your muscles are activated when you do
different exercises like squatting versus running.
And then in those different exercises,
which of your glute muscles are actually working.
Like, I know you can feel it when you're doing exercises,
but it's like a symphony of muscles working together
and you can't always hear the individual butt instruments.
That whole metaphor was just
so that I could say, "butt instruments."
But we also had a secret motive.
- That's cool.
- That's so neat. It's really cool.
- [Cassie] Now I need to find the exercise
that gives me the most.
- Maybe, I don't know, like depends
on what your goals are, right?
- Right.
- I think everyone wants a bigger butt.
- Cassie wanted to know how to get a big butt.
Look, this is not everybody's goal in life.
It's not necessarily mine,
but as far as trends in body shape go,
this one seems to be at least intriguing at the moment.
And we learned about how much exercise can actually affect
the shape and strength of your body.
I'm going to say right now that there are a ton of factors
that go into the strength and shape of your body, like diet,
exercise, and genetics.
That one, genetics, that one's
out of our control completely.
But if you're interested in the effect of exercise on
the shape of the strength of your body, let's charge onward.
First of all, do we even know what a butt is?
- Well, what do you mean by butt, right?
It's sort of the, whoever you're talking to.
- [Diana] Yeah.
- There's that saying that
if you have a hammer, everything looks like a nail, right?
So if you're talking to a biomechanist,
when you ask me about a butt, I thought,
"Oh, she means the hip.
And she means the hips rolling, running."
But if you talk to a nutritionist,
they're probably going to have
an entirely different interpretation.
- [Diana] Yeah.
Michael's point was that there's a lot going on
around your butt area. There's muscles, joints,
there's fatty tissues, which is mostly what contributes
to the average person's butt looking bigger.
- There's also bones around our butt, so if someone says
they broke their butt, they're probably talking
about the coccyx, or they broke their tailbone.
- Do people say that?
- Some people do.
- I broke my butt.
We get it, the butt can refer to a lot of things.
But since we're thinking about the effect of exercise on
the size of your butt, then we're going to focus
on the muscles.
There are three main muscles that most people
would consider comprising of the butt or the glute muscles.
The gluteus Maximus, the gluteus medius,
and the gluteus minimus.
But we focus on the gluteus maximus, the gluteus medius,
the lower back muscles and the thigh muscles.
There's a reason that we ignored the gluteus minimus.
- Gluteus minimus is the third.
- Where is that one?
- That's actually right below the medius.
So they do almost
identical things. - Oh, like right here?
- No, actually below as in deeper.
- Oh.
- Yeah.
- Beneath.
Since the gluteus minimus is covered
by the gluteus medius, we wouldn't be able
to use the electrode technology to get the signal from that
because it works by sensing
electrical activity of the muscles.
But since the gluteus medius is closer to the skin,
then you would probably unfortunately
get the signal from that muscle instead of the minimus.
Anyways, Michael placed the electrodes on our muscles,
and then when we activated a muscle,
the electrode picked up the electrical signal
from that muscle, transmitted it to the computer,
and we see the signal as this yellow graph readout.
- How is it measured?
- So it's measured in millivolts, so an electrical measure.
So it's how much the muscle is being recruited.
It's not the same
- [Diana] Recruited?
- [Michael] Recruited by the neural system.
So how much your body is saying,
"Okay, use this muscle a little bit. Use this muscle a lot."
It's not the same as muscle force.
So we're measuring the electrical activation
of those muscle fibers, essentially.
- It's literally like your brain is picking the muscle.
"I choose you."
On this configuration, we're seeing the gluteus maximus,
the gluteus medius, the paraspinals, or the lower back,
and the quadriceps.
The quads don't show up in every shot though,
because the electrode fell off.
- I'm still curious if seeing if squats
are more effective than doing like a butterfly bridge.
I'm just like curious.
- So we have to do a small series of things at a time.
- [Cassie] Okay.
- So what do you want to do first?
- [Diana] Cassie did four bridge exercises here,
a rolling bridge, one pushing forward,
single legged, and butterfly.
- [Michael] Then we would look at the amplitude.
- [Diana] Of these four exercises, the amplitude
of the gluteus muscles was highest
for the single legged bridge. That makes sense.
- [Michael] Look at the duration.
- [Diana] It looks like here, the rolling bridge
lasted longer than the pushing bridge.
- We can compare glutes to back.
This, version, right, had a higher ratio of backs to glutes.
- [Diana] That was the pushing bridge.
I guess you put your back into it.
- [Cassie] Look at how effective the one we did
this morning was.
This one.
You can't even compare that
because it's single leg, but look at that.
- [Diana] Yeah.
- [Cassie] That's like our version of the normal one.
- [Diana] Yeah, the butterfly?
- [Cassie] Mm-hmm.
- This burns!
- [Diana] Cassie then tried comparing squats, bridges,
and butt pulses, and we found something intriguing
about the move that had the most glute activation
in that set.
- Oh, so the butt pulse?
- [Diana] That's the butt pulse.
- [Michael] Oh, that's the butt pulse.
- [Diana] Wow.
- And that was the tiniest move. Whoa.
- Here's one factor to consider
is that you were at end range.
So when you do the butt pulse you're already
at full hip extension.
- [Cassie] Right.
- So you're taking the muscle.
A muscle can't produce as much force when it's short.
So you've shortened the muscle
and then you tried to create force.
So you had to use a lot of the muscle.
- That looked hard. Oh yeah.
- Uh-huh.
- Oh yeah.
- Uh-huh.
I make my students pulse all the time.
- Yeah.
- And they hate me for it. Now I know why.
- Yeah.
- [Diana] We tested so many other things,
like does Cassie get tired after 20 butterfly bridges?
No.
Does using a pointed versus a flexed foot
make a difference for butt muscle activation?
Not that we could tell when Cassie tried.
Unfortunately, Cassie had to leave after that,
but I was still super curious to test a more common activity
like running against a targeted glute exercise.
What is like, the glute exercise?
- [Michael] Probably squats.
- Squats?
- [Michael] A fitness person would probably say squats.
- So squats versus running would be a good comparison.
- I would guess we're going to see more activation
in running than in squatting.
- Interesting.
I was skeptical, but then I squatted for science,
then lunged for science, and then ran for science.
Squat, lunge, run.
- Circuit training.
So here we had the five squats.
Might've been a break here where we had
the lunges across the floor.
And then here we have the running all the way back.
So some of these big spikes are
because of the wire bouncing on each run,
but you can still see in between the spikes,
all that activity, the dense activity there,
and how much higher that is than the squatting
and the lunging. - [Diana] It's almost like
I didn't do anything.
- Muscles are generally more active
when they're slowing down in motion,
rather than when they're speeding something up.
- Yeah.
- And so since on every foot strike, when you're running,
your glute is activating to prevent you
from falling down, right?
- Yeah.
- So it's like, it's sort of absorbing
the impact of each step.
- Right.
So, yeah, we noticed that running recruited my glutes
more than squatting, but that doesn't necessarily mean
that running gives you the bigger butt.
It depends on how fast you run, for how long,
how many squats you do, and many, many other factors.
Also you run on one leg at a time.
So you have to control all your weight with one leg.
Whereas with a squat, the weight is distributed
between your two legs.
That could explain why we saw
a higher activation with running.
And I'm also a sample size of one.
That's not statistically significant. Statistically
signif-
That term cannot be said.
Statistically significant.
And actually one study found that long distance running
or swimming, might give you a leaner butt.
The study found that female athletes training
for these endurance sports had lean butts
that were no different from less active people,
but athletes in sports that involve sprinting and stopping
like soccer or squash, or jumping like volleyball,
have bigger gluteus maximus muscles than average.
- One example is figure skaters. Figure skaters
often have well-developed butts, right?
And part of the reason is because of their boots.
So I did my undergraduate research thesis looking at
the loading of your joints when you land flat-footed,
versus when you land with a pointed foot.
And when you land with the pointed foot,
your ankles take up a good portion of the loading.
- [Diana] Yeah.
- But when you're forced to land flat-footed
like you are in rigid figure skating boots,
the demand gets shifted to the hip.
So figure skaters having to land flat-footed all the time
are really absorbing a lot of that landing impact
with their hip muscles instead.
- Interesting.
So that's contributing to their large butts.
- So the sports you do can contribute to butt size,
but there's also this other thing to remember.
- I also want to add that the size of someone's butt is a
combination, both of the size of the gluteus maximus muscle,
but also the subcutaneous fat that's there.
- And also remember, whether working out
actually changes your body, depends on
a ton of environmental factors, your gender,
and other factors like your genes.
There's an interesting meta analysis on twins
that showed high heritability of things
like waist circumference, but then another meta analysis
showed low heritability of things like
cardio-respiratory fitness.
And yet another meta analysis showed that as you get older,
the contribution that food and exercise make increases
and the genetic contribution decreases.
There's a lot to it.
I will link to all of these studies in the description.
So if you want to try to contribute to the strength and mass
of your butt muscles, well, take up volleyball.
But also we saw the effectiveness of the activation
of your glutes with Cassie's butterfly bridges,
so go try out her workout. It just went out today.
It is the very first video of her 30 day,
hundred glute challenge.
I was day number one.
So there you have it, all of your butt questions answered.
Never thought I'd say that.
Thank you so much for watching, and
- Happy physicsing! - Happy physicsing!
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