How much exercise is too much? | Tim Noakes | TEDxCapeTown

Transcriber: Cathrine Ulstrand Reviewer: Emma Gon So you see what I don't understand is 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? " and I said, "I can't guarantee that you'll live. " However, fortunately, there's a picture of him diving in we were able to have him swim succesfully in the Arctic and in the Antarctic.

And what we're measuring here is his temperature response as he swims. And you'll see that his temperature drops very little during the swims and it drops mainly afterwards and this was a swim of 1 mile and you can see his body temperature drops quite dramatically near the finish and he was absolutely at the limit of his abilities. This is his muscle temperature which is much lower notice this is 32°C and even an hour an a half after getting out of the water his muscle temperature was still 32°C so he was just a warmed-up body centrally but his legs were still absolutely cold giving you an idea of how tough that was.

Here he's swimming essentially five years ago at the North Pole a picture of the South African flag. Now, the final topic is the one that's going to keep me going for the next twenty years is: Are low-fat diets healthy for you? (Laughter) (Applause) And where did it come from: in 1977, the American Senate decides that we must change our diets and we must cut out all the fat and we must put lots of carbohydrate in and that report was written by a vegan who had no training in nutritional sciences.

(Laughter) So this is what happened to your beautiful breakfast and I must just tell you that those eggs are one of the most nutritious foods that you could possibly eat. And what's the evidence against it -- there's lots. But let me tell you the French who do very well in terms of their hearts they do everything wrong as far as their diets they eat much more saturated fat but we now realise that there are populations that eat much less fat in their diet and have much more heart disease than these populations down here which eat a lot of fat and have very little heart disease.

So the concept that heart fat causes heart disease is completely bogus. And finally it's been realized -- there's a paper, a meta analysis and that's an analysis of all the studies that have ever been done and what it shows is this that there's no evidence that your dietary fat is associated with heart disease whatsoever. So if you're scared of eating fat you may now stop get rid of that scare here's the evidence for that case So what happened unfortunately as we went through this was that it took us millions of years to get to that and 27 years to get to that.

And this is directly related to the increased carbohydrate and processed foods we're eating in our diets. So finally, my summary Challenging Beliefs what I've learned in life is that 50% of what we teach is wrong the problem is we don't which 50% it is. (Laughter) (Applause) Our job as educated people is to spend our lifetime trying to figure our which 50% is which.

Until it is disproven accept that for which the evidence appears solid and logical and is free of covert or overt conflicts of interest because unfortunately, industry is driving what you believe in many many things. But don't ever dismiss lightly that that for which there's credible evidence that's reverse gullibility there's such clear evidence that the diets we're eating today are horrendous and we need to change them and we shouldn't be ignorant of that. Question everything else but eventually the truth has to prevail.

It always prevails. So aim to be on the side of the truth. Thank you very much for your attention.