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1:08

Somebody tells me there's going to be another heatwave. I think there's probably

1:11

going to be a lot of heatwaves. Crystal

1:14

ball time, isn't it?

1:19

Hello there and welcome to Inside Health. I've

1:21

come to Cardiff Bay because it has been

1:24

a red hot day, sun beating down the

1:26

whole time. But

1:28

here, by the water, there's a lovely

1:31

cooling breeze. We're

1:34

going to spend this programme trying to figure

1:36

out how hot is too hot for the human body. Because

1:39

with constant headlines of global

1:41

warming and rising temperatures all

1:43

around the world, it's an issue I think we need to

1:45

get to grips with. So I'm going to start

1:47

off by finding out what people

1:49

here think about the temperature. Do

1:53

you have two minutes to talk about the weather? Weather? Yeah,

1:55

really easy question. What

1:57

temperature's too hot? For me, never.

1:59

It's beautiful. Never. I

2:02

think like 28 is probably the peak of what

2:04

I can handle. I'd say like 33, 34 is like hot.

2:08

What happens to both of you when you get into like

2:10

the mid-30s? Smell into a puddle. Yeah, totally.

2:13

More than 20s, sound a bit iffy then. Oh,

2:16

God. I'd be

2:18

blocked away in the nice breeze or somewhere.

2:21

What happens to you when it's too hot? Oh, I'm big and hairy

2:23

so I sweat. About 50 degrees. About 50? Yeah,

2:26

yeah. I've been to Turkey

2:28

last year and it was 50.

2:31

Yeah, we had to go in then. I understand.

2:34

We don't mind it like this. It's got a little bit of a breeze. It makes everybody

2:36

happy, doesn't it? I'll be honest, I don't think I agree with 50

2:45

degrees. That

2:47

sounds way too hot for me, especially I've got

2:49

to work on that day. In a minute, we're

2:51

going to test my body in the laboratory

2:53

and see what it can cope with. But first,

2:56

I wanted to know what kinds of temperatures we're going to

2:58

have to deal with in the future.

2:59

Hello, I'm Professor Lizzie Kendon.

3:02

I'm strategic head of understanding

3:04

climate change at the Met Office Hadley Center.

3:07

Well, Lizzie, thank you for coming on. Must be a very busy

3:09

time at the Met Office. Not

3:11

that long ago we had the hottest June ever in the

3:13

United Kingdom. Is that a taste of what's to come?

3:16

So

3:16

it's not just been the warmest June on record. Last

3:18

year was the warmest year for the UK

3:21

and we have actually had a whole series of records.

3:23

In July last year, we reached 40

3:26

degrees C for the first time in the UK, which

3:28

absolutely smashed all previous records.

3:30

I really notice it just like in the space

3:32

of my near full decades of life.

3:35

I think that the summers now feel nothing like

3:37

they did when I was a child.

3:39

Our climate is changing. I think it's really important

3:41

to realize it's no longer just something that's

3:43

distant or far away from us or something in

3:45

the future. I think we are really seeing it now

3:48

here in the UK, you know, exceeding 40 degrees

3:50

C. That was practically impossible

3:53

had it not been for climate change. And as

3:55

we move into the future, these sort of temperature

3:57

extremes that we've experienced will become increasingly...

3:59

the common occurrence. Will they become

4:02

normal? I mean isn't that almost the

4:04

big question here kind of like what is our future

4:07

hot temperatures and summer going to be for us in the UK?

4:10

We do expect something like the hottest summer day

4:12

to increase by six degrees C

4:14

under a high emission scenario so that is a

4:16

huge increase by the end of the century but

4:19

you know the path that we follow is

4:21

not defined now it's in terms

4:23

of how we act over the coming years

4:26

is so very critical. Lizzie

4:27

thank you so much for coming on and explaining all that.

4:29

Thank you.

4:34

Well now I've come to the University of South

4:36

Wales to meet Professor Damian Bailey and

4:39

regular Inside Health listeners will remember

4:41

Damian from checking

4:43

me in a really cold room and we're going to do the opposite

4:46

today and go somewhere really

4:48

warm to see what the reaction is in my body

4:51

so Damian hi. Morning

4:53

James good to see you again. Lovely sunny day both

4:55

of us in shorts and t-shirts start contrast for the

4:57

last time I was here. Well it's like this every day

5:00

in Wales of course beautiful sunny day and

5:02

yeah we're going to be heating you up today

5:03

so it's going to be a lot warmer inside

5:06

than it is outside. Wow how

5:08

tempting that sweaty morning let's get on with

5:10

it. Great.

5:14

Okay James here we are we're in

5:16

front of the environmental chamber it's where

5:19

you were a few months ago but of

5:21

course you're exposed to cold heat today. Okay

5:24

what temperatures are we aiming for? So we're aiming for 35 degrees

5:26

centigrade 50 relative

5:29

humidity and we'll push it to 40 degrees

5:31

centigrade at the end of the exposure so typical

5:33

temperatures and humidities we'd encounter during a

5:36

heat wave. So we're going to go in and hopefully find

5:39

or get close to an answer for how hot is too hot

5:41

for the human body what are the changes that take place

5:44

when we're subject

5:44

to high temperatures and it just feels like it's a really important

5:47

question now doesn't it Damian because you can't

5:50

really escape news about how our climate

5:52

is changing and how things getting hotter. This

5:54

is becoming the new norm so absolutely

5:57

agree you know understanding the physiology and the counter

5:59

measures.

5:59

to try to prevent these changes,

6:02

you know, is essential. Shall we

6:04

go in? Yep, follow me, James. You're

6:07

up for view. I'll

6:11

just close the door. Okay,

6:14

so first thing I'm noticing is quite cool

6:16

in here, certainly compared with outside. So

6:18

it's thermonutral at the moment, 21 degrees centigrade

6:21

and 50% relative humidity. It's

6:23

like steel walls all the way around really

6:25

heavy doors, small little portholes looking

6:28

out into the rest of the world. It really does

6:29

remind me of an oven bin. Well,

6:32

it's probably not gonna be quite as hot as an oven,

6:34

but you will be sweating

6:36

and the body, the physiology is gonna change

6:38

quite considerably during the exposure. Well, I'm in

6:40

my lycra, ready to go. Short

6:43

some T-shirts, what's first? So

6:45

the very first thing that we need to test is

6:47

your metagenastics, your cognitive

6:49

ability. So this is short-term memory

6:52

and I'm gonna give you a list of 15 words. I'm

6:54

gonna say them out slowly and then

6:57

at the end of it, I want you to

6:59

repeat as many

6:59

of those words as you can possibly

7:02

remember. This is where I wish I'd done one of those how

7:04

to memorize sequences kind

7:07

of exercises. Okay, so you're

7:09

ready to go? I'm ready to go. So listening into

7:11

these 15 words. Drum, curtain,

7:15

bell, coffee, school.

7:19

["The Little Mermaid")

7:22

Turkey, house,

7:26

river. Okay, James, as many as you can

7:28

recall. Bell, is

7:30

that right? I

7:33

didn't know if I can remember the beginning. I've

7:35

got one. Curtain,

7:37

drum. I

7:40

do, this is terrifying. Grimber, farmer

7:42

and nose, house. Because

7:46

clapping my hands is gonna help me remember. No,

7:50

I'm done. Fantastic, well done, James, that was the first

7:52

part. I feel I need to warn you that I'm a naturally

7:54

quite sweaty person. In fact, sweating

7:57

in this environment, as you will find out, is

7:59

a good thing.

7:59

Okay James, so the first thing we need

8:02

to do is to get a fighting weight on

8:04

you. We want to measure your body mass.

8:06

So you've got shorts and boat

8:08

shoes and a lycra top on. What

8:10

I'd like you to do is to, behind the screen... Another

8:13

fashion week, here I come, right? Absolutely.

8:16

Strip everything off. Okay, can

8:18

I pass you my microphone? Sure. There you go.

8:21

The closer we can get to a

8:23

nude body mass, the better

8:26

when it comes to calculating sweat rates. Your

8:28

eyes only. And then when you're ready, stand

8:31

on the scales. I am on.

8:33

Test error 12. You're

8:36

kidding me. If you could just jump off

8:38

again. Yeah. And

8:41

then jump back on again. How much do you need?

8:45

88 points. It's all about the guns, right? Okay,

8:50

you can get yourself dressed

8:51

again. We're going to set you up with

8:53

all of the different bits of kit that

8:55

will allow us to make the measurements that we're going to make. Why

8:57

am I going to be wired everywhere? You will

8:59

be connected to the National Grid, but we'll be making

9:01

all sorts of measurements. So again,

9:03

we're interested in how the cart,

9:06

how the lungs, how the brain and

9:08

the muscles, how all of these organ systems

9:11

communicate to one another, and how the body

9:13

then responds to that heat stress. Let's

9:15

find out. Great. Okay, take a seat.

9:19

Just relax. Do you mind if I take your

9:21

glasses? We'll put

9:23

a headset on. We're going to measure how

9:25

quickly the blood is rushing into your

9:28

brain. By the way, that funny noise in the

9:30

background was gel being put onto

9:33

the ultrasound probe. So it might feel a bit

9:35

cold. Gooey. Yeah.

9:38

Yeah. You got me. We

9:43

got a tissue there. There's a bit on the microphone

9:45

here.

9:46

We're all squashed.

9:52

Okay, James, so you can hear that pulsatile

9:54

whoosh whoosh. It's a fabulous sound.

9:57

So you've just strapped a black box onto my own.

9:59

It's a little black box, so this

10:02

is known as a finger photo-pleth-mismograph.

10:05

So finger photo-pleth-mismograph. That's a big word. So

10:08

this is allowing us to measure beat

10:11

by beat arterial blood pressure.

10:13

From that, we're also going to assess

10:16

how much blood in liters per minute

10:19

is moving around your body. So that's known as your

10:21

cardiac output. Okay, so

10:24

we're placing the sticky electrodes

10:26

onto you now, James. So this is going to allow us to measure

10:28

your heart

10:29

rate in beats per minute. Blood

10:32

pressure is working nicely. Heart rate is working

10:34

nicely. All of the physiological

10:37

signals at the moment are telling me that you're in

10:40

spiffing shape. Okay, James.

10:42

So I'm going to pass you this mouthpiece.

10:45

So it looks a bit like a scuba diving

10:47

mouthpiece. It's going to allow us to calculate

10:50

oxygen uptake and carbon dioxide

10:52

output. And from that, we can determine

10:55

what types of fuels your body

10:57

is burning. Okay. There

10:59

you go.

10:59

Okay, so we're going

11:02

to do... Change the TUTA, James. I

11:04

didn't understand a word you said. But

11:06

James, what I'm going to ask you to do now is

11:08

just close your eyes nice

11:10

and relaxed. Give

11:13

me a left-hand thumbs up if you're okay. That's

11:16

great. Nice and relaxed. Try not to speak

11:18

and keep your head nice and

11:20

still.

11:21

Brilliant,

11:23

James. I'm going to place this into

11:25

your earlobe and I'm

11:28

going to get a temperature. Okay.

11:30

Everything that we need from you now we've collected in

11:33

the control condition. Well, I don't think I can go

11:35

very far at the moment, Damon, because I'm properly wired up

11:38

head to toe. So I've got a headpiece on.

11:40

I've got things all down my arm. Little

11:43

sensors plugged in and sellotaped to my body

11:45

all over the place. I'm going to dread taking those off

11:47

my hairy chest later, I think. So I'm a bit stuck here.

11:49

So subject me to your worst.

11:52

First I'm about to get the fans

11:52

on so you hear them kicking in

11:55

any minute. There we go. So what do I

11:57

have to do? Just sit and sweat. So

12:02

we've

12:02

gone from 21 degrees James, we're

12:04

currently at 23 degrees, all route to 35. It's

12:10

only gone up two but it's starting to go warm.

12:13

Absolutely.

12:19

So we're at the temperature that

12:21

we have targeted so we're at 35 degrees

12:23

centigrade now James. I'm feeling a little bit sweaty

12:25

under the armpits. Yeah. I'm

12:28

afraid to get off the seat. Okay,

12:30

we're going to stop the fast.

12:34

Okay James, so how are you feeling at the moment? Not

12:36

too bad. Like it is warm, I know that

12:38

it's warm but I'm just sat in the chair not doing anything

12:41

so it's kind of like I can feel like I can cope with this.

12:44

I can see the sweat. I wouldn't want to work in this temperature

12:46

though. Yeah and as you say you're doing nothing

12:48

you're... I think I'm glistening. I

12:50

think that's the word, bounce yes. What's

12:52

that noise? It's expansion there because everything's

12:54

been heated up. We can already see some of the

12:56

signs of what our bodies are doing in here. Just

12:59

the sweat. So you've got the evaporative heat

13:02

loss. You've also got a convective heat

13:04

loss so your skin is like

13:06

mine as well, it's a little bit redder. So

13:08

you've got what we call peripheral vasodilation

13:11

so those blood vessels have opened up just to try

13:13

to get blood to the periphery so that you're getting a

13:15

little bit colder. The thermostat

13:17

in the brain, the hypothalamus is

13:20

constantly tasting the temperature

13:22

to which you're exposed to and it sends

13:24

out all of these signals which we'll be measuring to

13:26

try to maintain homeostasis, to maintain

13:29

that comfortable set point. Okay James

13:31

so what we're going to do now is we're going to repeat all

13:33

of

13:34

the measurements we did in the control condition

13:36

now in the hot. So this is your

13:38

favorite part, this is the mental agility. Oh

13:40

not the words one. Again it's the

13:43

words so I'm going to ask you to recall 15 words.

13:46

Good to go. Good to go. Drum.

13:50

All I can feel is my body sweating. I can't even remember

13:52

if I've already said house, this is how badly I'm doing. You've snowed,

13:54

you haven't said house? Mmmhmm.

13:59

I think I've already said house.

13:59

I said turkey but I'm gonna say turkey again because I

14:02

feel like a roasted turkey right now. It's

14:04

gonna annoy me but I'm done. Good job, well

14:06

done, fantastic. Okay, so.

14:08

I'm feeling the heat now. You know when you see it was 35,

14:11

I was like, is it really, does it feel that bad? And now

14:13

I've been sat in it for longer, I'm starting

14:15

to go a bit melty now. Just creeps up

14:17

on it, isn't it? Yeah, my microphone's quite

14:19

slippy. So nice and relaxed,

14:22

so eyes closed as we make these

14:24

measurements and psychologically just preparing

14:27

yourself for an extra five degrees centigrade

14:29

to come as well. Thanks for

14:32

that. So we've collected

14:35

all of the information

14:39

that we need to collect now at 35 degrees centigrade.

14:41

We're all sweating. Shall we take it up to 40.3

14:44

degrees centigrade which was the hottest day

14:47

the UK's ever had? Absolutely, do you wanna go for it?

14:49

Let's try it. Okay. Because the

14:51

first time wasn't bad enough. Okay, right,

14:54

so we're gonna get the fans on again and

14:57

we're gonna take it up another 5.3 degrees.

15:05

Okay, James, so

15:07

we're at temperature now, the target. This

15:10

is 40 degrees centigrade, how does it feel? Brutal,

15:12

this is no longer pleasant. It just feels like it's

15:15

pounding on me now. Okay, so we're gonna

15:17

stop the fans and we're gonna repeat all of

15:19

the measurements again. Why am I feeling it

15:21

more now, Damien, than at 35? Because

15:24

we went from 20 to 35 and it's kind of

15:26

like okay, we're going from 35 to 40 and I'm kind of,

15:29

oh. It's just making it so much harder

15:31

for you to lose heat. I'm gonna need a very big towel

15:33

sometimes here. And a big

15:35

shower, I'd say. Yes. Okay,

15:41

James, so that's us, we're finished.

15:43

So we're gonna bring some cool air in now. Oh yes,

15:45

yes, bring me the cup. I

15:47

think we need to, we always do

15:50

sterilize the equipment at the end of this experiment before

15:52

we... Yeah, I feel sorry for whoever

15:54

has to use this next. All good? Yep.

15:57

Oh. Well done, how do you

15:59

feel?

15:59

I was surprised at the difference between 35 and 40. Both

16:03

feel very hot, but it was

16:05

a world of difference in terms of how it felt.

16:08

Sometimes it's

16:10

not linear, it's exponent, you know, it just gets, just

16:12

for that 5 degrees centigrade, it doesn't sound

16:14

much, but it really is physiologically so

16:17

much more of a challenge. One of the things I was thinking the whole

16:19

time in there was like, where is all of my

16:21

sweat going? I think we've

16:23

all been breathing it in. Yep, you

16:25

left a little puddle there. A

16:28

lot of it has

16:29

been absorbed into your clothes of course, but

16:32

we'll be taking all of those

16:34

off again and getting a new body mass, a

16:37

post-exposure body mass on you so that we can calculate

16:39

the sweat rates. Right, back behind the curtain. Well,

16:42

why don't you sweat down, James? I've got some roll

16:44

here. Thank you. So we want

16:46

to try to take as much of that

16:48

sweat off the way as possible.

16:51

Over as possible, yeah. And just throw it on the

16:53

floor, James, that's fine. And who wants this at the end

16:55

of the day? I don't know why producer Jerry is refusing

16:57

to make eye contact at the moment. Can't think for

16:59

the

16:59

life of my house. Weighing in at 87.8. Great,

17:03

thanks James. Loaded. So do you

17:05

need to do some number crunching now? We've

17:07

got all of your data, thanks so much for that. We've

17:10

got three sets of data. Okay, I'm

17:12

going to go get a glass of water while you do all that work, if

17:14

that's okay. You go for it. Don't feel sorry for me.

17:21

So Damien, you've

17:23

got the results, I can't wait. Okay, James,

17:26

the scores on the doors. So we'll

17:28

start off with how much volume

17:31

you lost, how much... I sweated off. You

17:33

sweated off. So you sweated off 400 Nls,

17:36

so just short of half a litre in

17:38

less than an hour, just sitting there doing nothing.

17:41

Your heart rate went from 54 beats

17:44

per minute at 21 degrees

17:46

centigrade, that's the control. It

17:48

went up to 81 beats per minute

17:51

at 35,

17:51

and rose further

17:53

to 87 beats per minute at 40

17:56

degrees centigrade. That's like I'm actually

17:58

exercising. Quite a big rise.

17:59

Your blood pressure was well defended throughout,

18:02

so your blood pressure was absolutely normal and

18:04

that's a good sign here. The cardiac output, which

18:06

is the volume of blood

18:08

circulating around the body, it

18:10

increased from 5.9 litres per minute to 6.8 litres

18:12

per minute at 40 degrees centigrade, mostly because

18:18

of the increase in the heart rate. Okay,

18:20

so why is the heart rate going up then? It's

18:22

looking to increase

18:24

the circulation of blood around the body

18:27

because, don't forget, the convective

18:29

heat loss, getting that

18:29

blood to the skin surface and

18:32

the vasodilation to try to get rid of the heat

18:34

is a key factor. You were ventilating

18:36

more, so in terms of litres per

18:39

minute, you went from 9 litres per minute

18:41

at 21 degrees centigrade to 17, so you

18:43

almost doubled. I'm breathing twice as hard.

18:46

Twice as hard. I felt like I was just doing

18:48

calm, relaxed breathing the

18:50

whole time. Because you're breathing more, you were blowing

18:53

the carbon dioxide off. The direct effect

18:55

that has is it causes a smooth

18:57

muscle around the arteries of the brain that

19:00

supply blood to the brain. They

19:02

constrict, they get a bit tighter. And

19:05

as a consequence, we saw a reduction in flow.

19:07

There's less fuel getting to my brain than as that rises.

19:11

So am I more stupid when it's hot? Good

19:14

question. I wouldn't use the term stupid,

19:16

I would probably say how does short-term memory

19:18

do. No difference between 21 degrees

19:20

and 35 degrees, but we started

19:23

to see the numbers drop at 40 degrees

19:25

centigrade. In terms of the word recall, you

19:28

went from 23 corrects to 17

19:31

at 40 degrees centigrade. So that seems

19:34

to be the tipping point between 35 and 40. My

19:37

body's big goal throughout all of this is to preserve

19:39

my core body temperature so that I don't basically

19:41

cook my heart and liver and lungs

19:43

and stuff, isn't it? Exactly. So

19:45

what happened to my core temperature? Core temperature

19:48

is maintained. A couple of degrees around that 37

19:50

degree set point. You did feel uncomfortable, but

19:53

the body is working really quite nicely

19:55

to try to defend and maintain that core temperature,

19:58

to maintain blood pressure, to... maintain

20:00

flow to the brain, but of course the numbers

20:02

are suggesting you weren't the same beast

20:05

at 40 degrees as you were

20:07

at 21 degrees. And that's in less

20:09

than an hour. And would that get worse if

20:12

I was in here all day? Yeah, for

20:14

sure. And if you were replacing those fluids,

20:17

it would get very much worse. I remember

20:19

last summer it felt like it went on for weeks. What's

20:23

the difference? It becomes cumulatively

20:25

that much tougher. It's a bit like saying, you

20:27

know, I'm going to run a 10K, but I'm

20:29

going

20:29

to run a marathon. The world's apart,

20:32

you know, and the physiological stress

20:35

is very, very different. Now, Damien, we

20:37

did all of these experiments at 50% humidity,

20:40

but humidity is really important because it affects your ability to sweat,

20:43

doesn't enter to lose the heat that way. So

20:46

I was catching up with some researchers that basically

20:48

did lots of experiments like this, comparing

20:50

different heats and different humidities to find

20:52

out what they thought was like the

20:55

problematic combination of the two.

20:57

So take a listen to this.

21:03

Hello, I'm Rachel Coddle.

21:05

I'm a PhD candidate at Penn State

21:07

University. Rachel, thank you for coming on Inside

21:09

Health. Thank you for having me. I suppose we should

21:11

explain, first of all, what is

21:14

humidity and why does it matter

21:16

in terms of how our body responds to heat?

21:18

Humidity is the amount of water

21:21

that's in the air and it matters because

21:24

during heat stress, one of the main

21:26

ways that we cool our bodies is through

21:28

sweating and the evaporation of that sweat.

21:31

The more humid the air is, the less likely

21:33

we're able to evaporate that sweat

21:35

from our body. So when it's more humid

21:38

out, we lose one of our main mechanisms

21:40

to cooling our body. And so our core temperature

21:43

rises faster and puts

21:45

us at greater risk for heat-related illnesses.

21:47

So in the experiments I've been doing,

21:49

Rachel, we've kept the humidity constant

21:52

and we've been playing around with the heat to see

21:54

what it does to my body. But you've been trying to work

21:56

out what's that dangerous combination of

21:58

heat and humidity.

23:54

particularly

24:01

large or high or scary

24:03

temperatures. These environments

24:05

that we're seeing as our critical limits are

24:07

happening over the globe right now. Not

24:10

only are these heat waves becoming more frequent,

24:12

longer in duration and more severe but they're becoming

24:14

more humid which is creating a greater problem.

24:17

And this is happening now, Rachel. In 2022,

24:19

India and Pakistan were hit

24:22

with a severe heat wave. Temperatures

24:24

were higher than these critical

24:26

temperatures and humidities that we've seen. It's

24:29

definitely a now problem, not

24:31

a future problem that we're seeing.

24:33

There seems something kind of almost sad about all

24:35

of this that I can imagine 20 years ago,

24:38

the kind of research that you're doing would have all been

24:41

about extreme sport or athletes

24:43

or expeditions and adventures and all that

24:45

kind of stuff. And now it's very

24:48

much about the

24:50

changing face of our planet and the conditions people

24:52

are living in already.

24:53

Yeah, exactly. And the fact that

24:55

so many people die during these

24:58

extreme heat waves, honestly,

25:00

most of these deaths can be prevented,

25:03

especially with proper cooling strategies

25:05

and just general awareness

25:07

of the public of who's at

25:09

risk and what to do during these heat waves.

25:12

Rachel, thank you so much for coming on the program. Hey,

25:14

you're welcome. Thank you again for having me. So

25:18

what did you make of that? There's a whole gamut

25:20

of physiological stresses

25:23

that are going to challenge us as time goes by. And

25:25

there's a very strong argument that our physiology

25:27

is going to have to change quite aggressively to

25:29

cope with these environmental stresses because it's

25:31

changing so rapidly. So when

25:34

we're trying to answer the question of kind of like how hot is

25:36

too hot for the human body, is

25:38

there an easy answer to that? The

25:40

way we respond to heat is very individual.

25:43

So it's very difficult to say. When

25:45

the core temperature rises, you're

25:48

going

25:48

to about 37.4 degrees centigrade,

25:50

but people that are getting increasingly

25:53

hot, they can't find a cool place.

25:55

They're not replacing fluids. If the core temperature

25:57

rises to about 39.5 degrees, centigrade,

26:01

you know, they become what we call syncopated, very

26:03

light-headed, very dizzy, very

26:05

prone to fainting and again

26:08

the reason for that, they're not getting enough blood. I think

26:10

I've had that once. Yeah, so

26:12

it's pretty miserable. Once the core

26:14

temperature rises to around about 42 degrees

26:16

centigrade, of course, this

26:19

is where we start to see really, really

26:22

significant problems and if not

26:24

treated, you know, the individual will actually die

26:26

as a result of, you know, they've succumbed to, you

26:28

know, to the heat, to hypothermia.

26:29

Lots of people may be

26:32

listening to this programme thinking, I used

26:34

to go on a nice foreign

26:36

holiday in those kinds of temperatures, why

26:38

are you talking about that

26:40

as though it's a scary thing I used to celebrate going

26:43

on holiday in that kind of temperature? You're gonna leave

26:45

the lab today with a smile on your face. All

26:47

of your statistics coming through in terms of integrated

26:49

physiological response are telling me that you have

26:52

risen to that challenge and you've beaten that

26:54

challenge and you've done a jolly good job. That's

26:56

fair a thought for the older people that are

26:58

less physically conditioned, people

26:59

that are suffering from disease, you

27:02

know, patients with congestive heart failure, lung

27:04

failure, you know, patients that are

27:06

diabetic, patients with dementia or

27:08

Alzheimer's, that, you know, every

27:11

day it's a battle, it's a physiological

27:13

challenge for them. Now when you throw in

27:15

an extra-stricer, heat and humidity,

27:18

you know, sometimes they can't rise to that challenge.

27:20

Damien,

27:24

do you have any top tips for

27:26

coping with the heat? You know, keeping it simple

27:29

really, James, to me is key. As you

27:31

saw yourself, you've lost 400ml there over less

27:33

than an hour. It's not just

27:35

a case of just quickly drinking 400mls of water,

27:37

you know, it's about

27:39

slowly drip, drip, drip feeding to

27:41

maintain that. Try not to grab doors, certainly

27:44

try not to exercise in the

27:46

hottest part of the day. Another tip as well is

27:48

try not to get sunburned. Even a mild sunburn

27:51

can knock out the ability to thermoregulate or

27:53

to sweat,

27:54

you know, functionally sweat for up to as long

27:56

as two weeks. So... Two weeks? I've

27:58

never heard of that. Which is worse?

27:59

So the evidence is suggesting

28:02

there are more excess deaths as a result of the cold

28:04

snaps relative to the heat

28:06

waves that we see. But of course with

28:09

time, we're not really sure how

28:11

these things are playing out because we are seeing clear changes

28:13

in the climate. If we get hotter summers and milder

28:15

winters. Exactly. David, thank you so much for

28:17

having me. Lovely to see you, James. And

28:20

yeah, look forward to you coming back.

28:24

Well, I've come

28:26

back to Cardiff Bay because

28:29

I'm a little bit tired after all those experiments this morning. The

28:31

fatigue has really set in now. I

28:34

couldn't believe the difference between 35 and 40 degrees. I

28:38

thought I was coping really well. Then it got

28:40

really hot. So I'm just cooling

28:42

my body off now, enjoying the breeze. And

28:45

all I can do is wish you a nice

28:47

cool summer. I think

28:49

I'm going to go get myself an ice cream.

28:55

Hello, I'm Dr Michael Moseley.

28:58

And in my new BBC Radio 4

29:00

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29:03

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29:28

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