We’re taking on an age-old question today: Do kids have more energy than adults? Breakfast tacos, caffeine, an energized DJ and an epic family battle. This episode has all that and then some. Discover how we turn food into energy at an awesome taco party. Then pump up the jams with DJ Thyroid. Speaking of music, get ready for a song from Lake Street Dive’s Mike Olson. And just when you think the show might be out of energy, we engage in an out-of breath competition between a girl and her parents. Plus, there’s a brand new Mystery Sound and a Moment of Um about why we lose our voices sometimes.

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DEMINKA: You're listening to Brains On!, where we are serious about being curious.

ANNOUNCER: Brains On! is supported in part by a grant from the National Science Foundation.

MOLLY BLOOM: I have never been more ready for a taping in my life. I have my 2 and 1/2 cups of coffee right here in this novelty-sized goblet, the exact right amount to give me energy but not jitters.

[SLURPS]

I've got supportive footwear. And I've got the right music to pump me up.

[MUSIC PLAYING]

This music is so great. It makes me want to move. Look at me. I'm dancing. A few high kicks, some light tap dancing.

[TAPPING]

Now I'm doing the worm. I didn't know I could do the worm. I feel like I could do 50 jumping jacks. Why not? Who says kids have more energy than adults? Ha-ha. This is wearing me out. How many jumping jacks am I at, like 10? I need to lie down or maybe drink some more coffee. Where's my goblet?

[SLURPS]

There we go. Let's do this.

[MUSIC PLAYING]

This is Brains On! from American Public Media. I'm Molly Bloom, and my cohost today is Deminka from Colorado Springs, Colorado. Hi, and welcome.

DEMINKA: Hello, Molly.

MOLLY BLOOM: So, Deminka, on a scale of 1 to 10, 10 being the highest, what is your energy level right now?

DEMINKA: I would say at nine because I'm pretty excited.

MOLLY BLOOM: Awesome. So what is like a full on 10 for you? What is that like?

DEMINKA: I just feel like everything will go perfectly and nothing bad could ever happen. I just feel like I'm walking on air.

MOLLY BLOOM: That sounds like an excellent feeling. So like when does that happen? When do you feel that feeling?

DEMINKA: Like sometimes after I've just like won maybe a really important game or I just get something really important or very special that I wanted to get.

MOLLY BLOOM: So it sounds like your energy level might be tied to things that are happening like your emotions?

DEMINKA: Yeah. I would say that it was.

MOLLY BLOOM: So what about a one? How do you feel like when you're like a one for energy?

DEMINKA: I just feel like nothing could ever work out. And if it does and I go, it must be some sort of mistake or accident.

MOLLY BLOOM: So we are going to explore the well of energy inside all of us today. It was something we were very curious about after hearing this question.

HARLAN: Hello. My name is Harlan, and I live in Shrewsbury, Massachusetts. And my question is, why do kids have more energy than adults?

MOLLY BLOOM: So, Deminka, would you say that you have more energy than your parents?

DEMINKA: Definitely. I just feel like I'm always running or jumping or playing catch with our dog or something. But my parents are always like, woo, that's a long game of catch. Let me sit down for a second. I'm like, how could you be sitting down?

MOLLY BLOOM: Us poor adults, we just don't have the energy to match. So are there other times where you're like, come on guys, let's do something. And they're like can I just drink another cup of coffee?

DEMINKA: Yeah. Well, for my mom, it's the morning. And for my dad, it's at night.

MOLLY BLOOM: Well, that's good. At least you have one who's awake at different times of day maybe. So, Deminka, I was wondering now that you can't go to school and get energy out that way, are there things that you found to help you burn off your extra energy?

DEMINKA: When I was at school, I would walk the halls a lot because I would have to go from my homeroom to my advanced math and then back to my homeroom. So I'd have to walk a lot. And so now I'll just go outside, and I'll ace up and down the yard and up and down the yard because it just gets my legs. They get tired after 30 minutes or so.

MOLLY BLOOM: Well, before we get to the kids versus grown up energy question, we should start with the basics.

DEMINKA: How do our bodies get and use energy in the first place?

MOLLY BLOOM: We asked Brains On! producers Marc Sanchez and Sanden Totten to help break this down for us.

SANDEN TOTTEN: Hey, you two.

DEMINKA: Hey, Sanden. Is that a cart full of--

[SNIFFS]

Breakfast tacos?

SANDEN TOTTEN: Yep. It's part of our demonstration.

MOLLY BLOOM: Speaking of which, where's Marc?

SANDEN TOTTEN: Marc's going to be late.

MOLLY BLOOM: Really? I didn't get a text from him or--

SANDEN TOTTEN: Oh, oh, he doesn't know he's going to be late-- yet. You see, I snuck into his room yesterday and set his alarm for later than usual.

MOLLY BLOOM: I'm pretty sure Marc would be upset if he found out you changed his alarm.

SANDEN TOTTEN: Oh, don't worry. He hasn't found out. I watched him make sure on the cameras I installed in his room.

MOLLY BLOOM: Sanden.

SANDEN TOTTEN: No, no, no. He knows about the cameras. He knows about the cameras, I promise. He agreed to be filmed as part of this demonstration. The alarm is the only part he doesn't know about. Well, the alarm and the tacos. Let me just call up the live feed here.

[STATIC NOISE]

There we go. See? Marc is still sleeping.

[SNORING]

DEMINKA: Aw, look at those cute pajamas. They're covered in drawings of-- dancing pickles?

SANDEN TOTTEN: We'll get to Marc in a second. But first, Molly, Deminka, have a breakfast taco.

DEMINKA: Thanks. Looks delicious.

[CRUNCHES]

MOLLY BLOOM: This is so good. Thanks, Sanden.

SANDEN TOTTEN: So the story of energy in our bodies begins with food. In this case, tacos.

[MUSIC PLAYING]

Soon, your body will digest that brekky taco by breaking it down into lots of different things, like vitamins, minerals, and a special kind of sugar called glucose.

MOLLY BLOOM: Mm, glucose.

SANDEN TOTTEN: Glucose is super important for energy. Your stomach and your small intestine will take in that glucose and pass it on to your bloodstream. From there, it'll swim around and can pretty much go anywhere in the body. Some of it will be stored in places like the liver or in muscles or fat cells. That's so you can use it later. But before glucose can power your cells, it needs to be broken down even further into something called ATP.

DEMINKA: Awesome Taco Party!

SANDEN TOTTEN: No, no. That's not what ATP stands for.

DEMINKA: No. I mean, this is an awesome taco party. Can I have another, please?

SANDEN TOTTEN: Oh, sure. Here you go.

DEMINKA: Yes! Thank you.

SANDEN TOTTEN: So ATP actually stands for Adenosine Triphosphate. Think of glucose like a big chunk of gold. And ATP is like actual dollars and cents. A big chunk of gold is worth a lot, but you can't just go to your local grocery store and buy oatmilk and gum or juice with it. First, you need to exchange that gold for cash. ATP is that cash.

[DINGS]

And it's your cells that do the exchanging. They take the glucose and break it down into a few different things, including a bunch of ATP molecules. Then, your body can start spending that ATP energy on important things, like exercise, studying, playing.

MOLLY BLOOM: Or reaching for another taco. Yoink.

[CRUNCHES]

SANDEN TOTTEN: So now that we've covered how our bodies get glucose from food and how our cells break down that glucose into ATP--

DEMINKA: Which is basically energy money our bodies spend to do stuff.

SANDEN TOTTEN: Yep. So how do our bodies spend that ATP? This is where Marc comes in. And he should be waking up right about now.

[ALARM]

MARC SANCHEZ: Another beautiful day. What? I'm late!

[CLAMORING]

Oh my gosh. Oh my gosh.

SANDEN TOTTEN: OK, so Marc hasn't had breakfast yet, so where is he getting all this energy from? Well, his muscles and yours have a tiny amount of ATP stored in them. So that first moment Marc jumped out of bed, that was him using that ATP that was just chilling in his muscles.

MARC SANCHEZ: No time to find matching socks. I'll just wear sandals.

SANDEN TOTTEN: But that ATP in the muscles runs out pretty fast. In about 3 seconds. So next, the muscles turn to a chemical in them called creatine phosphate. The muscles can break down creatine phosphate pretty quickly to make more ATP. It's like having a check you can easily cash for some dollars and cents.

MARC SANCHEZ: I can't forget to comb my teeth and brush my hair-- I mean, teeth my hair and comb my teeth. I mean, whatever! I got to go!

SANDEN TOTTEN: But your muscles can only use creatine phosphate for energy for a short while, too. Like 8 to 10 seconds. Perfect if you're lifting weights or swinging a bat or kicking a soccer ball. So next, Marc's muscles will start using glucose stored in the form of glycogen. Glycogen is a chemical that can be broken down to make glucose, which, as we talked about, can be broken down to make more ATP.

But as you can imagine, all this breaking down from one thing to the other takes more time. So this process is slower. But probably right about now, Marc's body is getting energy this way.

MARC SANCHEZ: Right, quick check. Keys, wallet, pants. Yep, yep, yep. OK, I'm ready to sprint to the studio!

SANDEN TOTTEN: But alas, using glycogen only works for about a minute and a half. To run all the way to the studio, well that's going to require some long lasting energy. Which means Marc needs oxygen. Oxygen can help break down more glucose into glorious ATP energy money.

[DINGS]

But this process takes even longer than the other ones I mentioned. So it doesn't really kick in until you've been active about two minutes. When that happens, it's called aerobic respiration.

MOLLY BLOOM: Oh, like aerobic exercises. I do those at the gym sometimes.

SANDEN TOTTEN: Exactly. These types of exercises need long lasting energy, so they rely on this aerobic respiration to keep you full of ATP. And that's how your body makes and uses energy.

MARC SANCHEZ: Hey, sorry I'm late. Alarm problems. Did I miss the demonstration?

SANDEN TOTTEN: Nope. In fact, you are right on time, Marc.

MARC SANCHEZ: I am?

SANDEN TOTTEN: Yep. And you did your part perfectly. Now, look what I brought you.

MARC SANCHEZ: Breakfast tacos! Yes! I'm so drained. I had to run all the way from my house.

SANDEN TOTTEN: I figured you'd be hungry. Look, I even got extra pickled onions.

MARC SANCHEZ: Delicious. What an awesome taco party.

DEMINKA: That's what I said. Hand me another one, Sanden.

MOLLY BLOOM: Me, too.

MARC SANCHEZ: Me, three! That first one is donezo.

SANDEN TOTTEN: All right, all right. Plenty of tacos to go around. Enjoy that glucose, everybody. Get that ATP. Chow down.

MOLLY BLOOM: OK, Deminka. I hope you're feeling recharged.

DEMINKA: Yep, and full of tacos.

MOLLY BLOOM: Great. Because you need to be alert for this next one. It's the--

[MYSTERY SOUND CUE]

AUDIO TRACK: Mystery sound.

MOLLY BLOOM: Here it is.

[RHYTHMIC BEATS]

OK. Deminka, what is your guess?

DEMINKA: I don't know. I just heard a rhythmic thumping. Reminded me of a ball bouncing. But then I also heard this tiny crack sound, almost like plastic knocking against each other. So I'm not sure. I guess maybe a gym.

MOLLY BLOOM: Excellent, excellent guess. Well, we're going to give you another chance to hear it and guess a little later in the show.

AUDIO TRACK: Brains, Brains, Brains On.

MOLLY BLOOM: We don't just use energy when we're running around. We actually use it all the time.

DEMINKA: Yeah. It takes energy to keep your heart beating, your lungs breathing, and your brain thinking.

MOLLY BLOOM: In fact, you're burning energy constantly, even when you sleep. And different people burn energy at different rates. We call that rate your metabolism. And it's controlled in large part by this gland called the thyroid.

DAWN BELT DAVIS: It looks a little bit like a butterfly.

DEMINKA: That's Dawn Belt Davis.

MOLLY BLOOM: She's a physician and teaches at the University of Wisconsin in Madison. She is an endocrinologist. This is the type of doctor that studies hormones and how they keep the body in balance.

DAWN BELT DAVIS: It has two butterfly wing shapes which we call the lobes on either side. And then it has a little thin area in the middle. So it runs right across the front of your neck where your voice box would be.

MOLLY BLOOM: The thyroid makes hormones, which are like chemical messages your body uses to control all kinds of stuff, like your growth, your digestion, and your mood.

DEMINKA: The hormone that the thyroid makes is called-- wait for it-- the thyroid hormone.

MOLLY BLOOM: Props for keeping it simple.

DEMINKA: Yeah. The thyroid uses this hormone to help control your energy levels. And it's constantly pumping out that thyroid hormone.

DAWN BELT DAVIS: You could think of it as like a volume switch maybe on your music or something. So you would turn it up if you need a little bit more, and then you turn it down. But there's always some volume.

MOLLY BLOOM: It's almost like the thyroid is a DJ and your energy levels are a nonstop dance party.

THYROID: Hello, my party people!

[PARTY HORN]

Are you ready to rock, DJ-DJ-DJ Thyroid?

DAWN BELT DAVIS: So the thyroid actually tends to tell your body to use up the food that you've eaten and turn it into energy.

THYROID: All right, cells. Grab some food, grab some stored glucose or fats. And get ready to jam! I'm going to play that special ATP-making music. So let's break down some glucose. Can I get a yeah?

CROWD: Yeah!

THYROID: Can I get an oh yeah?

CROWD: Oh yeah.

THYROID: Here we go!

MOLLY BLOOM: So when you need more energy, DJ Thyroid sends signals to your body to start using the energy stored in fat or in your liver.

DEMINKA: It also helps control your body temperature. And when we're running low on energy, the thyroid helps make us hungry. So we eat and refuel.

MOLLY BLOOM: And get this. The thyroid even helps control our moods.

DAWN BELT DAVIS: The thyroid also can act back at the level of the brain. You can think of it as activating the nervous system and activating certain parts of your brain. And that can lead to increased energy, which is thinking of energy in terms of how you feel, right? Do you feel excited? Do you feel anxious? Do you feel ready to go, or do you feel slow and sluggish and depressed?

And so thyroid hormone is going to push you more into that excited, anxious, ready to go energy level or feeling than if you don't have enough thyroid hormone, then you may feel slow and sluggish and depressed.

THYROID: How you feeling tonight?

[GROANS]

I can't hear you. We need to boost that mood! That's better. Now, I said, how are you feeling tonight?

[CHEERS]

That's more like it.

DAWN BELT DAVIS: The balance is basically to keep you right where you need to be in the middle and not way too slow and sluggish and not way too fast and ramped up.

DEMINKA: Another really important part of the energy story is sleep.

MOLLY BLOOM: Ah, sleep. One of my favorite hobbies. Remember how we told you that ATP stands for adenosine triphosphate?

DEMINKA: And not awesome taco party?

MOLLY BLOOM: Right. Well, when you use ATP for energy, your body is breaking apart that adenosine triphosphate. One of the pieces left over is called just adenosine.

DEMINKA: Makes sense to me. ATP has adenosine in the name, after all.

MOLLY BLOOM: So as you go about your day, you use ATP and create more and more adenosine. In the brain, this adenosine sits on brain cells and makes them sluggish and tired.

ADENOSINE: Hello, brain cell. It's me, adenosine. Mind if I sit on you?

BRAIN CELL: I mean, I guess?

ADENOSINE: Look into my eyes. You are getting sleepy. You're getting very sleepy.

MOLLY BLOOM: The longer you're awake burning ATP, the more adenosine builds up in your brain, making you more and more tired.

DEMINKA: Eventually, you'll fall asleep. And luckily, your brain uses that time to clear out the extra adenosine. So you wake up feeling nice and refreshed.

BRAIN CELL: Huh? What happened? Get out of here, adenosine!

ADENOSINE: Oh, I shall make my retreat. Bye!

MOLLY BLOOM: Cool fact. Caffeine, the chemical in coffee that wakes you up, is super similar looking to adenosine. So when you have caffeine, it goes into your brain and sits on the same spot of the cell that adenosine would normally fit into, basically blocking it. Except unlike adenosine, caffeine doesn't make you tired.

ADENOSINE: Hello again, brain cell. Mind if I have a-- who's sitting in my seat?

BRAIN CELL: It's caffeine.

CAFFEINE: Yeah, this seat is taken. So scram, adenosine.

ADENOSINE: You haven't seen the last of me. I'll be back. And then you'll have to sleep!

DEMINKA: So that's part of how caffeine helps give you energy.

[MUSIC PLAYING]

MOLLY BLOOM: Coming up, the battle we've all been waiting for. The ultimate test. Who has more energy?

DEMINKA: Kids--

MOLLY BLOOM: Or adults?

DEMINKA: Stick around.

MOLLY BLOOM: Hey, you. Yeah, you listening right now. We've got super exciting news. We've written a book. It's called Brains On! Presents It's Alive. It's all about the wild world of living things, from narwhals and neurons, to flowers and fungus. Plus, it's got colorful comics, mystery photos, and lots of mindblowing science facts. It's Brains On, but for your eyes. It comes out September 2020-- that's this September. But you can preorder it now so you're the first to get it.

Just go to bit.ly/brainsonbook. That's bit.ly/brainsonbook.

DEMINKA: If you could build a very tiny robot, what would it do?

MOLLY BLOOM: Would it herd dust bunnies under your bed, or climb in your nose to trim your nose hairs? Deminka, what would your microbot do?

DEMINKA: My microbot could sense when something was dropped on the floor to be able to push it away and put it where it's supposed to be so you wouldn't have to clean. It'd be really small. It would camouflage to the wall so you'd never be able to see it.

MOLLY BLOOM: That sounds like an excellent robot to have around. Now what do you think this robot would sound like? Ooh, a silent robot. Excellent. Well, we are doing an episode about the smallest of robots. And we want your ideas. Send us a recording describing a tiny robot you'd build, and make sure to let us know what it would sound like, too.

DEMINKA: Just go to brainson.org/contact.

MOLLY BLOOM: You can also go there to send us a question, like this one.

ANDEL: Hi, Brains On.

ALITA: I'm Alita.

EVA: I'm Eva.

NORA: I'm Nora.

ANDEL: I'm Andel. We're from Portland, Oregon.

NORA: And our question is--

ALITA: Why do you lose your voice when you yell really loudly or talk for a while?

DEMINKA: We'll answer that at the end of the show in our Moment of Um.

MOLLY BLOOM: Plus, we'll read the latest group of names to be added to the Brains Honor Roll.

DEMINKA: Don't miss it.

MOLLY BLOOM: Welcome back to Brains On from American Public Media. I'm Molly.

DEMINKA: And I'm Deminka.

MOLLY BLOOM: And you know what's always a good energy booster? Some music. We have a song that tries to answer why adults seem so tired all the time.

DEMINKA: It's by our pal Mike Olson he's part of the band Lake Street Dive. Hit it.

(SINGING) I think I've got it all worked out. I notice why my parents are so tired all the time. I'm just not sure if I should tell my brother and my dog that Mom and Dad are fighting crime. I think that they're superheroes. It's the only explanation why when they finally get home that all they want to do is put their feet up and stare at their phones. Because their superheroes.

I'm guessing Mom has super strength and the ability to fly. And Dad would be so stretchy. Yeah, he's just that kind of guy. They save the city just in time for my morning cartoons. Insisting they're accountants, but I know they're playing cool. Otherwise they'd have more energy, I know. Which is why I think they're superheroes.

I'll tell you all the things that I do. I go outside and play and sing show tunes all day. I re-arrange my entire room. Then write a Broadway show and teach myself banjo. There's always stuff to do, I agree. All kinds of books to read and garden slugs to feed. I spend an hour on my trampoline. Then climb a dozen trees, the lap of luxury. But I'll never understand why my demanding kind of schedule leaves me energy to spare.

It's becoming quite apparent my poor parents need their rest far more than me. It's totally not fair. I think that they're superheroes. It's the only explanation why when they finally get home that all they want to do is put their feet up and stare at their phones. Because they're superheroes. Maybe Mom has X-ray vision to stare right through the walls. And Dad could push a button on his suit to make him super small. Or maybe he could make his skin turn green and burrow underground and she could reach out with her brain and move the furniture around.

Or maybe grown-ups just have got a life that's on their mind. And raising kids is hard even when in the best of times. Otherwise they'd have more energy, I know. Which is why I think they're superheroes. Believe me that they're superheroes. I just know my folks are superheroes. My Mom and Dad are superheroes.

MOLLY BLOOM: So yes, I'd say we can all agree that parents seem tired a lot, especially when compared to their kids.

DEMINKA: So it's time to answer the question, why?

MOLLY BLOOM: But we also have to ask, do kids really have more energy than adults, or does it just seem that way?

SAM URLACHER: Yes, the kids do have more energy than adults, depending on how you look at it.

DEMINKA: That Sam Urlacher.

SAM URLACHER: I study how kids have evolved to use energy to do all of the things that they need to do in life, like play, like fight off infections, like grow.

DEMINKA: When you look at how active kids are, they have the adults beat.

SAM URLACHER: We know that kids do move around a lot more and are much more physically active than adults are. So if we look, for example, in the United States, the average six-year-old moves about twice as much as the average adult does. So between the age of 6 and about 18 or 19, kids end up moving about 4% less each and every year until they reach adult levels.

MOLLY BLOOM: And there are other differences between kids and adults that make it easier for kids to have more energy.

SAM URLACHER: Kids sleep about two more hours every day than adults do. And your body uses fewer calories when you're sleeping, so that saved energy could be reallocated towards times when you're awake. And you can move around more. I think another thing to remember is that kids are just much smaller than adults. So I think kids can imagine, if you had to walk around all day with a heavy backpack full of rocks, it would be really hard, right? And you'd have to spend a lot more energy to do the same things.

So since adults are just bigger, it's like they're carrying around that big backpack all the time. Kids that are smaller can just do more activity because it costs less to move themselves around.

DEMINKA: But why? Why did kids evolve to be so energetic compared to their parents?

SAM URLACHER: We see that being a kid is actually a stage of life that's distinct to humans. Chimps, they're born. They're babies, and then they grow up relatively fast. So when we go back and look at fossils from our human ancestors that anthropologists dig up in the ground, we see this extended development in childhood started to evolve around 2 million years ago. And progressively, kids remained kids for longer and longer up to our own species and how we are today.

MOLLY BLOOM: So in our ancient ancestors, kids didn't stay kids for that long. Maybe a few years. But as our ancestors evolved, childhood got longer and longer.

DEMINKA: Scientists don't exactly know why we evolved this way. But they do have some ideas.

SAM URLACHER: To be a successful human adult, you need to, of course, learn to do lots of things. So kids having more energy and more time to grow up might allow them to play, to explore. To otherwise practice all those skills that they need to learn before becoming adults.

DEMINKA: So kids have a lot to learn, and they need a lot of energy to do that. But don't we need energy to grow, too?

SAM URLACHER: Any organism or any human, any kid has a certain number of calories. A budget that they can spend to grow, to fight off infections, or to move around and play. To do all these things. It seems like we have evolved childhood specifically to have very low rates of growth.

MOLLY BLOOM: So between the time you're a toddler to when you're a teenager, your body is focused on growing your skills and your brain. You definitely are still growing your body, but not as fast as other times.

SAM URLACHER: We grow much faster as infants, where we're obviously not moving around much. And we grow much faster as adolescents during a growth spurt, where we also are moving less by that point.

[VOCALIZING]

AUDIO TRACK: Brains On.

MOLLY BLOOM: There are also some physical differences in the bodies of kids and adults that help us understand why kids seem to have so much more energy. Brains On producer Menaka Wilhelm created a little game for you and your parents to help us explore this.

MENAKA WILHELM: Yup. Menaka here, ready to referee. I brought my whistle.

[WHISTLES]

I'm wearing my black and white referee stripes. And comfortable running shoes, of course. And my outlook on life is gruff but fair. So, Deminka, we asked you and your parents to do a series of physical challenges before today's taping. Did you get to do them?

DEMINKA: Yep.

MENAKA WILHELM: Great. Let's jump right into that first around. The heart rate recovery test. The point of this round was to see who's better at going from resting to playing to resting. So we had to do 30 seconds of Jumping Jacks, and you measured your pulse three times. Before the jumping, right after the jumping-- that's when your heart was thumping the loudest-- and then again, after you rested for 2 minutes. The goal is to see who's heart went back to being calm and steady faster.

MOLLY BLOOM: All right. Deminka, how did it go?

DEMINKA: Well, my resting heart rate is 96 beats per minute. After Jumping Jacks, it came up to 132 beats per minute. And then 2 minutes later, I was at 104 beats per minute. Now my mom went from 80 beats per minute to 132 beats per minute after exercising. And then 2 minutes later, it went down to 92 beats per minute. And then my dad went from 84 beats per minute. After the Jumping Jacks, 128 beats per minute. And then 2 minutes later, it was 104 beats per minute.

MENAKA WILHELM: So after that 2 minutes, sounds like your heart rate was closest to your resting heart rate, Deminka.

DEMINKA: Yeah. Seems about right.

MENAKA WILHELM: In that case--

[WHISTLES]

The point goes to Team Kid.

[CHEERS]

Zach Gillen, who's an exercise scientist at the University of Nebraska, told me that because of the way adults' hormones and their body systems work, grownups take longer to switch into and out of activity mode.

ZACH GILLEN: Whereas kids, they can just get out and get going. And they're good to go. And then right afterward, go back inside and be resting and recovering.

[MUSIC PLAYING]

MENAKA WILHELM: Round two, the long jump. For this round, you started from standing still, and then you did your biggest jump forward. And you measured or you marked the length of your jump to see whose was longer. Deminka, have you done long jumps before?

DEMINKA: I've done once or twice in PE, but that was pretty much it.

MENAKA WILHELM: Well, this round is a challenge for your muscles. So who jumped longer at your house, Deminka?

DEMINKA: Mom was 48 inches, I was 59. But my dad went all the way to 80 inches.

MENAKA WILHELM: What?

DEMINKA: I know.

[WHISTLES]

MENAKA WILHELM: The point goes to Team Grownup.

[CHEERS]

And that makes sense. Your parents are bigger than you, plus our muscles change as we get older. We think about two kinds of muscles. So one kind is called slow twitch muscle, and the other kind is called fast twitch muscle. Fast twitch muscles are really good for doing a big jump like this. Slow twitch muscles are better for running around at a steady pace for a long time. And kids naturally have more slow twitch muscles, Zach told me.

ZACH GILLEN: Whereas adults have more of those fast twitch muscle fibers, which are more powerful and stronger. But they're more fatigable. They can tire out a lot quicker.

MENAKA WILHELM: Round three, a balance challenge. For the final round, we asked you to see who could stand on one leg for longer.

MOLLY BLOOM: Deminka, the suspense is killing me. Who balanced longer?

DEMINKA: My mom. But she only beat me by like 8 seconds.

MOLLY BLOOM: So you were very close. And how'd your dad do?

DEMINKA: He got out in the first 30 seconds. But my dog started licking him, so he fell over because he was laughing.

[LAUGHS]

[WHISTLES]

MENAKA WILHELM: One point to Team Grownup.

[CHEERS]

ZACH GILLEN: So the reason adults are more coordinated is as you get older, basically your brain is able to turn on and activate more of your muscle and use more of that muscle.

MOLLY BLOOM: Do we have a winner? Kids or adults?

MENAKA WILHELM: Well, before we name our winner, kids definitely have a lot of energy. And they're different from adults in a couple key ways that help them play a lot. They're better at switching between rest and activity, and their muscles are great at keeping going. But adults are usually stronger and also more coordinated. Leah Robinson studies kids and exercise at University of Michigan. And she says there's something else that drags adults down a little bit when you think about their energy levels.

LEAH ROBINSON: They are thinking about work and responsibilities. And concentrating and thinking takes up energy. We might not think of it that way, but it does.

MENAKA WILHELM: Oh, responsibility. The age old energy drain. OK, so for our challenge--

[CLEARS THROAT]

[WHISTLES]

With two points, the winner is Team Grownup.

[CHEERS]

But that parent win has a lot to do with the things we get better at as we get older, like balancing. So in the end, we'll name you both winners. That was Leah's idea.

LEAH ROBINSON: Both of them are winners if they both do it and get it done, because it's a great family child activity. And I'm a supporter of anything that gets parents and children working together, being outside, and being active.

[WHISTLES]

MENAKA WILHELM: Thank you all for playing!

[MUSIC PLAYING]

MOLLY BLOOM: OK, take a sec to catch your breath, Deminka. And while you're resting, let's hear that mystery sound one more time.

[RHYTHMIC BEATS]

All right. Deminka, any new thoughts?

DEMINKA: It sounded like jump rope this time. One of the jump ropes that doesn't have all the beads and stuff on them. It's just the rope part. So I'm guessing that someone's doing some kind of exercise, like jump rope.

MOLLY BLOOM: Excellent, excellent guess. Here is the answer.

JUSTIN: Hello. Our names are Justin.

AMELIA: And Amelia.

JUSTIN: We are from Hamilton, Ontario.

AMELIA: And the sound that you just heard was me skipping on my skipping rope.

MOLLY BLOOM: Deminka, you are 100% correct.

DEMINKA: Yay!

MOLLY BLOOM: Skipping rope, jumping rope. Same thing. You got it right. Excellent work. Have you jumped rope before?

DEMINKA: Well, I've tried, but I'm not that good at it. AKA, I'm really bad at it.

[LAUGHS]

But I have a friend, and he's really good at it.

MOLLY BLOOM: Can he do fancy tricks and stuff?

DEMINKA: Yes.

MOLLY BLOOM: Very impressive. I always wanted to be able to do that. But also, cannot. It's a goal to work towards. I just got to get some energy to do so.

[RHYTHMIC SKIPPING]

[MUSIC PLAYING]

Our bodies break down food into glucose and then ATP. It's that ATP that powers our muscles.

DEMINKA: The thyroid helps to keep our energy levels steady so we're not too hyper and not too sluggish.

MOLLY BLOOM: Kids are great at switching between resting and playing and playing for a long time.

DEMINKA: But adults are often more coordinated. We get better at different things as we get older.

MOLLY BLOOM: It's easier for kids to have more energy to spend, and they probably evolved this way so they could spend a lot of energy learning all the skills they need to be adults one day. That's it for this episode of Brains On.

DEMINKA: Brains On is produced by Molly Bloom, Marc Sanchez, Sanden Totten, and Menaka Wilhelm.

MOLLY BLOOM: We had production help from Ruby Guthrie and Christina Lopez, engineering help from Johnny Vince Evans and Peter Ecklund. Special thanks to Monica and Richard Claudnickey, Melanie Renee, Coco Sanchez, and Vikki Krekler.

DEMINKA: Brains On! is a nonprofit public radio podcast.

MOLLY BLOOM: You can support the show and help us keep making new episodes at brainson.org/fans.

DEMINKA: Now before we go, it's time for our Moment of Um.

AUDIO TRACK: Uh. Um. Um. Um. Um. Um. Um.

DEMINKA: Why do you lose your voice when you yell really loudly or talk for a while?

[VOCALIZING]

JENNIFER LONG: I'm Dr. Jennifer Long. I'm an otolaryngologist, which is an ear, nose, and throat doctor. And I especially specialize in care of the voice. So first, I think we need to understand how your voice is produced. So your voice comes from your voice box, which is right in the middle of your neck. And within the voice box, which is also called the larynx, you have two paired vocal cords. Those are really tiny little bit of tissue that produces all of that energy that comes out as our voices.

In grownups, they're about an inch long. It's a little bit smaller than that in kids. And they have to come together and collide. So the two vocal cords actually hit each other many, many times in order to produce the sound waves. So as I'm talking right now, that collision process is happening about 200 times every second.

If you're screaming so that your voice is way up at a higher pitch, that's happening even faster. It's more like 500 times a second. And then the other factor is, of course, the loudness. To talk louder, you have to bring up more air flow from your lungs. You also have to use more of the muscles that are around the vocal cords to hold them together and stiffen them. And also there's more area of the vocal cords that are making contact with each other when you're speaking loudly.

So to get back to why we lose our voice when we're speaking loudly or yelling, is that those vocal cords are pretty delicate little things, and they're just not meant to undergo that much trauma. So you can think about it like if you're walking with shoes that are a little bit too small and your skin is rubbing and you develop this blister on your foot. Something similar happens in the vocal cords. If they're colliding against each other for too long, they will develop almost like a callus and some fluid that builds up inside them.

Once that happens, the vocal cords can't do that nice vibration to produce the sound waves. So that's what's happening at the tissue level when we're feeling like we can't produce our normal voice.

AUDIO TRACK: Um. Um. Um.

MOLLY BLOOM: My voice is ready to read this list of names. It's time for the Brains Honor Roll. These are the brilliant listeners who have shared their questions, ideas, mystery sounds, drawings, and high fives with us.

[LISTING HONOR ROLL]

AUDIO TRACK: Brains Honor Roll. High fives.

MOLLY BLOOM: We'll be back soon with more answers to your questions.

DEMINKA: Thanks for listening.

Transcription services provided by 3Play Media.