"Hey, David. Now the biggest rule in extreme heat is to keep drinking water, we all know that.You're losing so much of it at the temperatures like this, but there is something you don't always think about. But when you actually see how much water you can lose as we did yesterday, it's alarming!"

 

We went to Crunch Gym to show you the effects of heat and humidity on your body by sitting in a steam room. My weight before the steam--197.6 pounds. I also take my pulse-- 72 beats/minute. 

 

"I'm going into the steam room with this device. It's gonna tell me both the temperature and humidity. When you put those numbers together, it gives you the heat index that tells you how dangerous it is outside,how much water your body is gonna lose during the heatwave."

 

The steam so intense, a camera won't even work inside.And it only takes a few minutes to have an effect on my body.

 

"My pulse is now 128. That's one of the first things to go up when you get too hot."

 

In extreme heat, your heart starts pumping faster to try to dump heat and sweat into the air. My pulse up 56 beats. Of course, this room is deliberately intense, with a heat index over 170, and you've stayed in just 20 minutes. That may seem high. But in Minnesota, their recorded heat index is over 130. After 20 minutes, we do another weighing. This time, I'm 196.2-pounds.

 

"(I) lost a pound and a half of water in 20 minutes just sitting."

 

In Chicago where the heat index was 112. ABC's Matt Gutman tested some runners, measuring their pulses and weight ("52.") before they set off for a two-mile run. ("Good luck!") When they finished, Matt found both runners lost about a pound of water each, and their heart rates more than doubled.

 

"My body feels like it's on fire."

 

"And Richard's back. It's really something to see just how much water you lost and how quickly always important to point it out.But I want to ask you about two different things that you were telling me are less obvious when you actually stop sweating in this kind of heat."

 

"You know that's right. You know, which your body do when it's sweating is releasing heat into the air. And that's so important to regulating your body. But when you stop sweating, that's saying you've lost so much that your bodies try to maintain its blood pressure and it is calling back. And your body can overheat in just minutes doing that to a deadly level."

 

"And so it's important that we all keep our eyes on our neighbors and people who are most vulnerable in the heat. And you were saying when someone looks pale, most of us would grant when with this kind of feature:("That's right.") when you look pale, that's a warning sign."

 

"That's right. It's the same thing.Your body,instead of sending blood to your skin to release heat, it's clamping down to maintain the blood pressure, and that person needs treatment right away."

 

"All right. Richard Besser, thanks so much."

 

"What you've said, over and over plenty water,plenty, plenty water. ("Drink, drink.") All right, Richard."