why I have to go through all this pain.

But when I do see something I don't agree with

I become addicted to try to answer what is the truth.

Today I'm going to talk about some of the ideas

that I've focused on.

They come in many different topics

and you can see they cover

medical problems in marathon runners.

Rugby injuries. Are all rugby players overplayed?

Something about nutrition.

Should we be eating carbohydrates

or should we be eating fats?

And particularly what regulates our exercise performance?

And then, is it possible to swim at the North Pole

at -1.8°C in a speedo?

So I'm going to talk about those questions

and I'm going to begin by the very first question

that ever came to me as a scientist was:

Are marathon runners immune to heart disease?

And this was a theory developed

by a Californian pathologist

and he said on the basis on any contrary evidence,

it looked like if you ran a marathon

you'd never have a heart attack.

So I mean I knew that it was absolutely bogus

but to prove it was all the more difficult.

At the time in the 1970s

this was the bible of running.

It was written by James Fixx

and he described at length the whole hypothesis.

Tragically seven years after this picture was taken

James Fixx died of a heart attack while running.

But by then we had in fact already shown

that it was possible for people to have heart disease.

So we looked for when we saw reports of people

dying in marathon races

we would go and collect their hearts

and we would examine them

and eventually we found the evidence

and so we published a paper

in the New England Journal of Medicine

showing that there were runners who had disease

and the disease here is -- this is coronary artery disease

in which there's obstruction of the coronary arteries

causing heart attacks and we were able to show

that this man had had a heart attack whilst

he was running a marathon.

So that was published and so that disproved

that's obviously very easy to do, it's easy to find a few cases

that disprove a theory.

The next one that I really got involved with

is in the 1980s was:

Should we be drinking more or less during exercise?

And at the time in the 1960s

it was held that actually if you drank during exercise

that wasn't a very good idea.

Abebe Bikila who was the first African runner

to win two Olympic gold medals

in the 1960 and 1964 Olympic marathons

he ran both races without drinking anything.

That was what runners did in those days.

And then all of a sudden in the 1960s and 1970s

things changed and we were told that

if you didn't drink enough, you were going to die during exercise.

I became interested in why that would be the case.

And the epiphanous moment occurred on 1 June 1981

when an athlete started the Comrades Marathon in Bourbon

and she reached 70 km

and her husband withdrew her from the race

because she didn't recognise him

and he felt that wasn't a good idea. (Laughter)

And he then took her for medical care

and in short order within two hours

she was unconscious having epileptic seizures,

and she had to be taken back to hospital in Bourbon.

And when she was admitted to hospital

she became the first case of this condition

which -- a long name we don't need to understand

what it is at the moment.

But here's her chest x-ray and this shows

that she's got fluid in her lungs

and it took five days later

before the fluid had gone out of her lungs

but this is what happened what really happened

was that her blood sodium concentration

which should normally be at 140 and is tightly regulated,

it's one of the most regulated features of the body

had dropped to 114 that's heroically wrong,

something had gone tragically wrong

and she asked me what had happened

and I said, "We have absolutely no idea."

and it was the first case in the world

so we had no idea.

Over the next four or five years

we picked up couple of more cases and

worked out that they probably had overdrunk

and in other words

they'd drunk too much during exercise.

And then at the 1988 Comrades Marathon

we could prove it by hospitalising eight people

who were really sick with this condition

and follow them during their recovery

and we were able to show

that they all passed an excess of fluid

during recovery and so this athlete here

passed six litres of fluid extra during recovery

and that she had dropped her blood sodium concentration

to a very low level

and you can see there was a nice relationship.

So the more you overdrink

the lower your sodium

and the sicker you were

and we published that in 1991

and thought that's the end of the problem.

We cured the problem,

we know what causes it, it's overdrinking

and we thought the problem would go away.

But unfortunately at the same time we were doing that,

industry would come along and said,

"No actually, the more you drink, the better."

So there's an advert

saying that not only must you drink

but you must drink heroically during exercise

this is 1.2 litres per hour

or your performance will suffer.

And we predicted what would happen,

we predicted this would happen.

And this is the incidence of this condition

accumalative incidence of this condition

which had never existed before 1981, never existed

There were a total of 1600 cases in the medical literature

this is not all cases because many were not recognised

and tragically twelve deaths,

all completely avoidable.

And so what happened was that

the sports drink industry came along then

and then they influenced the official drinking guidelines

drawn up by official bodies

and those promoted overdrinking.

Then a lady died in the Boston Marathon in 2002

and in 2003, I was invited by two organizations

to produce alternate drinking guidelines

which promoted drinking to thirst

and that finally has now been accepted that

that is the way we should be drinking.

But you can see what the cost of that disease

that had never existed came along.

And finally the book written about

the whole sorry thirty-year saga

was released recently.

And what I was able to show was that

the science of hydration is utterly bogus.

There is no science to it,

it was dreamed up by marketers to sell a product

and I'll come back to that point in due course.

The next question that really has intrigued me was:

Do muscles regulate exercise performance

or is it something else?

And it's really interesting in sport that you see

such close finishes.

And this was the 2000 ten thousand meters in the year 2000

and you can see that Haile Gebrselassie has won this race

by a few inches

and it's a race that goes on for twenty-five minutes,

so how can a twenty-five-minute race

come down to a few centimeters?

And the argument is that the reason why the athlete

comes second is because his muscles

offers too much lactic acid

and that causes him trouble

so the athlete who comes second,

his heart is unable to pump enough blood to his muscles

so they become anaerobic and

as a consequence they produce lactic acid

which you all learned in biology

causes muscle poisoning and stiffness

and everything that goes wrong in sport

is a related to this terrible product lactic acid.

Over time, it took us a few years

but we realised this model can't be right

it can't be true

for a very simple reason.

That it's brainless.

Fatigue in this model is caused exclusively

by the failing muscles.

So the brain can't influence your performance.

So what you think is utterly completely irrelevant.

All of you know that's rubbish

because motivation must have a role

in some way in sporting performance.

So we did a lot of research

and then finally we realised what the evidence was.

Again it just takes one insight to see these things.

This is Haille Gebrsellasie running 10 000 meters.

This is his average pace for each kilometer

and what do you notice?

He runs the fastest the last kilometer.

But how can that be?

How can he run his fastest when he's most fatigued?

And all that tells you is that fatigue

as we describe it

has got nothing to do with the physical side of your body

because he's performed much better

when his muscles are the most tired.

So therefore we worked out that fatigue is purely an emotion

it's what your brain is making up

it's completely fallacious

emotional information that your brain uses

to make sure that you don't die during exercise. (Laughter)

And so we eventually came up with this model

the Central Governor Model of Exercise

which originally was critizised

when we proposed it in 1996.

People said, "You're mad! How can it possibly be true?"

I'm glad to say that there are multiple Olympic athletes

at this very moment training according to this model

and acknowledging it

that they are now training

because they understand performance.

And what this model says simply is that

the brain regulates your muscle performance

and that feeds back to your brain

and then there are other factors like

motivational factors and I see my time is running

so I'll have to go a bit quickly.

That there are a whole bunch of factors

that influence your brain

and then you start exercise at a particular work rate

which is different depending on how far the activity is.

You always have reserves

you always finish with,

you could always exercise harder.

There's always an end spurt

and finally, there's always feedback to the brain.

So that's the way the system works.

And as I've indicated

it's now becoming accepted.

The next question:

Is it possible to swim 1 km at -1.8°C

in only a speedo?

The person who asked me that question was Lewis Pugh.

We, just approximately five years ago

travelled to the North Pole

to swim have him swim 1 km

and I had to make sure he returned alive.

It all began when he said,

"Can I swim around the Cape Peninsula?"

and I said, "Yes"

and everyone else had said, "No. That's impossible."

So he went out and swam around the peninsula.

It took him thirteen days

but he managed to do it.

And when he finished he said

"Can I now go and swim at the North Pole

or in the Arctic where the temperature is 0 to 5°C?"