Welcome to brain Stuff from how stuff Works dot com where smart Happens. Hi Am Marshall Brain with today's question, why shouldn't you go swimming right after you eat a meal. I don't know about your mother, but my mother had a hard rule when I was a kid. Don't go swimming for an hour after you eat was something I heard constantly when I was little. And the funny thing is when I look back at it as an adult from a how stuff works perspective, she was right. But
we should be clear. If you're splashing around in the shallow into the pool, it really doesn't matter. What we're talking about is swimming like in a deep lake or an ocean, where you're really swimming. And it's true, if you're gonna be really swimming, you should wait about an hour before you go in the water. So what's going on here? Your body is a system made up of subsystems, and all of those subsystems need energy. Your brain needs energy,
Your muscles need energy. They have energy demands. When you're swimming hard, like in a deep lake or in the ocean, you're using a lot of muscle energy. Well, there's another system in your body that also needs energy. And that's your stomach and small intestines, and it needs its energy most when you're digesting food. So right after you eat, your stomach and your small intestines are going to be
putting energy demands on your body. Usually we don't notice the energy demands of our stomachs because after we eat, we usually go watch TV or lie down or sit in a chair or something like that. It's only when you have two systems competing for energy that you really notice these energy demands. So if you go and eat a large meal and then you swim a mile out into the ocean, that's where the energy needs of two
systems are going to clash. Your stomach and your small intestines are trying to digest the meal, and your muscles need a lot of energy because you're swimming hard. When that happens, the competition between those two systems means that something's going to lose out, and this is where you
get cramped. Your muscles are asking for energy that's just not there because the stomach is sucking up some of it, and the response of your muscles to the lack of energy in this case, oxygen nutrients that normally come in blood flow is for them to start cramping. And from this description you can see that this would really apply to any kind of exercise. You wouldn't want to go eat a huge meal and then go run a marathon five minutes later either. The competition between your stomach and
your muscles when running a marathon would be a disaster. However, if you're running a marathon and you get some cramps, you're not to die. You can just pull over and rest on the side of the road. It's when you're in the water and you get cramps and you have a real problem because you can drown that you have to worry about the cramping. The easiest way to solve this problem is to wait for about an hour to allow some digestion to occur and food to leave your
stomach before you do any real swimming. For more illness and thousands of other topics. Because that how stuff works dot com and don't forget to check out the brain stuff blog on the how stuff works dot com home page. You can also follow brain stuff on Facebook or Twitter at brain stuff hs W