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Speaker 1: Welcome to brain Stuff from how stuff Works dot com

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Speaker 1: where smart Happens. Hi Am Marshall Brain with today's question,

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Speaker 1: why shouldn't you go swimming right after you eat a meal.

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Speaker 1: I don't know about your mother, but my mother had

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Speaker 1: a hard rule when I was a kid. Don't go

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Speaker 1: swimming for an hour after you eat was something I

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Speaker 1: heard constantly when I was little. And the funny thing

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Speaker 1: is when I look back at it as an adult

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Speaker 1: from a how stuff works perspective, she was right. But

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Speaker 1: we should be clear. If you're splashing around in the

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Speaker 1: shallow into the pool, it really doesn't matter. What we're

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Speaker 1: talking about is swimming like in a deep lake or

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Speaker 1: an ocean, where you're really swimming. And it's true, if

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Speaker 1: you're gonna be really swimming, you should wait about an

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Speaker 1: hour before you go in the water. So what's going

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Speaker 1: on here? Your body is a system made up of subsystems,

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Speaker 1: and all of those subsystems need energy. Your brain needs energy,

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Speaker 1: Your muscles need energy. They have energy demands. When you're

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Speaker 1: swimming hard, like in a deep lake or in the ocean,

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Speaker 1: you're using a lot of muscle energy. Well, there's another

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Speaker 1: system in your body that also needs energy. And that's

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Speaker 1: your stomach and small intestines, and it needs its energy

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Speaker 1: most when you're digesting food. So right after you eat,

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Speaker 1: your stomach and your small intestines are going to be

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Speaker 1: putting energy demands on your body. Usually we don't notice

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Speaker 1: the energy demands of our stomachs because after we eat,

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Speaker 1: we usually go watch TV or lie down or sit

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Speaker 1: in a chair or something like that. It's only when

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Speaker 1: you have two systems competing for energy that you really

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Speaker 1: notice these energy demands. So if you go and eat

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Speaker 1: a large meal and then you swim a mile out

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Speaker 1: into the ocean, that's where the energy needs of two

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Speaker 1: systems are going to clash. Your stomach and your small

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Speaker 1: intestines are trying to digest the meal, and your muscles

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Speaker 1: need a lot of energy because you're swimming hard. When

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Speaker 1: that happens, the competition between those two systems means that

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Speaker 1: something's going to lose out, and this is where you

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Speaker 1: get cramped. Your muscles are asking for energy that's just

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Speaker 1: not there because the stomach is sucking up some of it,

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Speaker 1: and the response of your muscles to the lack of

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Speaker 1: energy in this case, oxygen nutrients that normally come in

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Speaker 1: blood flow is for them to start cramping. And from

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Speaker 1: this description you can see that this would really apply

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Speaker 1: to any kind of exercise. You wouldn't want to go

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Speaker 1: eat a huge meal and then go run a marathon

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Speaker 1: five minutes later either. The competition between your stomach and

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Speaker 1: your muscles when running a marathon would be a disaster. However,

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Speaker 1: if you're running a marathon and you get some cramps,

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Speaker 1: you're not to die. You can just pull over and

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Speaker 1: rest on the side of the road. It's when you're

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Speaker 1: in the water and you get cramps and you have

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Speaker 1: a real problem because you can drown that you have

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Speaker 1: to worry about the cramping. The easiest way to solve

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Speaker 1: this problem is to wait for about an hour to

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Speaker 1: allow some digestion to occur and food to leave your

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Speaker 1: stomach before you do any real swimming. For more illness

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Speaker 1: and thousands of other topics. Because that how stuff works

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Speaker 1: dot com and don't forget to check out the brain

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Speaker 1: stuff blog on the how stuff works dot com home page.

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