0:00:03 > 0:00:06Are you ready for our out-snips? Snip!Ouch!Exactly!
0:00:10 > 0:00:12It's hot versus cold.
0:00:12 > 0:00:14We're putting our bodies to the test
0:00:14 > 0:00:17to see how they react in extreme temperatures.
0:00:17 > 0:00:20Behind this glass, it's colder than the freezer in your kitchen.
0:00:20 > 0:00:22It's actually colder than the North Pole.
0:00:22 > 0:00:27In fact, it's colder in here than the coldest place on Earth.
0:00:27 > 0:00:28That's Antarctica.
0:00:28 > 0:00:32This is a cryogenic chamber and I'm going to get inside.
0:00:32 > 0:00:35And I've come to Loughborough University to find out
0:00:35 > 0:00:37what happens to the body when you get hot.
0:00:37 > 0:00:40I'm going to be running in a room set to 50 degrees Celsius.
0:00:40 > 0:00:43That's the same temperature as the hottest place on Earth,
0:00:43 > 0:00:45Death Valley!
0:00:45 > 0:00:46Time to get changed.
0:00:46 > 0:00:48Me too!
0:00:48 > 0:00:51So, clearly, I'm going to need a very warm coat to go in there?
0:00:51 > 0:00:54No, just very, very small clothes. Not very warm clothes.
0:00:54 > 0:00:58This doesn't look like nearly enough clothes.
0:00:58 > 0:01:01I might be cold but at least I'm going to look stylish.
0:01:01 > 0:01:03Headband, vest, shorts,
0:01:03 > 0:01:05two pairs of socks, clogs
0:01:05 > 0:01:08face mask, gloves.
0:01:08 > 0:01:09I told you I'd be looking good.
0:01:09 > 0:01:11Er, if you say so, Xand!
0:01:11 > 0:01:15A cryogenic chamber is normally used to treat common health conditions
0:01:15 > 0:01:19or help top athletes recover from injury, but today I'm using it
0:01:19 > 0:01:23to find out how our bodies would react in extreme cold.
0:01:23 > 0:01:26It's so cold in there that our cameraman can't come in.
0:01:26 > 0:01:29But I have my own special camera, so you're coming with me.
0:01:29 > 0:01:31Whoa!
0:01:34 > 0:01:35OK...
0:01:35 > 0:01:39..it's very cold but it's quite manageable.
0:01:39 > 0:01:42So the room I'm in at the moment is as cold as the coldest temperature
0:01:42 > 0:01:43ever recorded on Earth.
0:01:43 > 0:01:47But this room is just preparing my body for the next room,
0:01:47 > 0:01:49which is twice as cold.
0:01:49 > 0:01:52But first, Chris, how are you getting on?
0:01:52 > 0:01:54I've got to run on this treadmill in this room,
0:01:54 > 0:01:56which is kept at 50 degrees Celsius,
0:01:56 > 0:01:58and I promise you that is really hot.
0:01:58 > 0:02:02If your bath was this hot you'd burn yourself.Off you go then.
0:02:02 > 0:02:05This is causing my body temperature to rise dramatically.
0:02:05 > 0:02:08If it rose too high it could be fatal,
0:02:08 > 0:02:11but our bodies are amazing at keeping us cool.
0:02:11 > 0:02:14So I need to lose heat and it's very hard to lose heat
0:02:14 > 0:02:16when the air around you is hotter than you need to be.
0:02:16 > 0:02:19The only way you can do it is by sweating.
0:02:19 > 0:02:22# So hot in here. #
0:02:22 > 0:02:26So the reason we sweat is to take heat energy away from our bodies
0:02:26 > 0:02:29and this helps to cool us down.
0:02:29 > 0:02:33Your body also has some clever tricks to keep you warm.
0:02:33 > 0:02:34I'm moving into the second room now
0:02:34 > 0:02:37which is a chilling minus 135 degrees!
0:02:37 > 0:02:40That's far colder than anywhere on Earth.
0:02:40 > 0:02:43It's very hard to describe quite how cold this is.
0:02:43 > 0:02:45The closer I get to the floor...
0:02:45 > 0:02:48HE SHUDDERS LOUDLY
0:02:48 > 0:02:50This is now very, very, very, cold.
0:02:50 > 0:02:52I'm getting goose bumps all over my arm
0:02:52 > 0:02:58and you can see every single hair on my arm is standing straight up.
0:02:58 > 0:03:01The reason that's happening is that my body is trying to trap
0:03:01 > 0:03:05a layer of air very close to my skin
0:03:05 > 0:03:08and...I'm shaking a lot.
0:03:08 > 0:03:12Shivering like this is my body getting my muscles moving
0:03:12 > 0:03:14to generate heat and keep me warm.
0:03:14 > 0:03:18As my hand gets cold, you can see all the blood goes out of my skin
0:03:18 > 0:03:22and now my fingertips are going absolutely white.
0:03:22 > 0:03:23Very, very cold indeed.
0:03:23 > 0:03:27That's because, as my body gets colder, it's making a choice.
0:03:27 > 0:03:30It's taking the blood away from the parts of my body it can do without,
0:03:30 > 0:03:33like my fingers and toes, and putting it into the centre
0:03:33 > 0:03:37of my body to keep vital organs like my heart and brain alive.
0:03:42 > 0:03:45Chris, how are you looking? Um, sweaty!
0:03:45 > 0:03:48The sweat Chris is producing is not only full of salt,
0:03:48 > 0:03:51there are other things lurking in there too.
0:03:51 > 0:03:55In fact, sweat is a lot like your pee, it's a lot like urine,
0:03:55 > 0:03:56so you can think about that
0:03:56 > 0:03:58next time you're licking it off your upper lip.
0:03:58 > 0:04:00Gross!
0:04:00 > 0:04:03And just like we've seen with Xand, our body is clever at keeping
0:04:03 > 0:04:06the most important areas safe from changes in our temperature.
0:04:06 > 0:04:08While I've been running,
0:04:08 > 0:04:11the sweat experts have been monitoring how much I've sweated.
0:04:11 > 0:04:15So we've just measured me and I'm a kilo lighter now than I was
0:04:15 > 0:04:19at the beginning of my run and that is that much sweat that I've made.
0:04:19 > 0:04:22So we've shown you how your body sweats away the extreme heat
0:04:22 > 0:04:24to keep you cool.
0:04:24 > 0:04:28And my body re-routed warm blood away from my hands and feet
0:04:28 > 0:04:30to look after the important inner organs.
0:04:30 > 0:04:33Our bodies are amazing.
0:04:33 > 0:04:35See you next time.Bye!Bye!
0:04:35 > 0:04:37Bye!Bye!Bye!
0:04:37 > 0:04:39Bye.By-y-y-e!
0:04:39 > 0:04:41THEY MOUTH: Bye.