THE OPTIMAL FUEL FOR CYCLISTS? | INTERVIEW WITH DR. TIM PODLOGAR part 1 of 2

Interview with exercise physiologist Dr Tim Podlogar about the new isotonic drink produced by Slovene experts and numerous myths that circulate among cyclists.

Image 1: When Tim isn't in his lab, he's on the road.

Tim, you once mentioned that the first thing you’d take on a deserted island with a paved road to a 3,200 meters high volcano is an isotonic drink. Why is it so important?

You forgot the bike. Without a bike, a quality drink would only keep me alive longer.

Jokes aside, carbohydrates are a source of energy. They are the most important source of energy during intense physical activity. And the amount of carbohydrates in the body is greatly limited, which means that sooner or later the moment comes when we run out and then we hit a wall.

If we want to maintain high intensity, we have no other choice but to constantly supply our body with carbohydrates. And no, it is not enough to start ingesting carbohydrates during exercise once we already feel depleted – we must do it from the very beginning. This will slow down the consumption of carbs stored in the body.

We must be also aware of the fact that the body does not store fuel the same way a car does. A car functions normally until the gas runs out, but the body is different. One of the things that happen when carbs start running out is that the body starts burning muscle, and many people experience muscle cramps.

And it’s not only about one training session, but the next one as well. A certain level of micro tears in the muscle is normal, but if it’s too much, the next day we might not be able to train properly.

And there’s also the issue of hydration. Which is quite crucial on a volcano (laughs).


Video 1: Carbohydrates (CHO) have an important role during training sessions, and even more so during a race. No other nutrient can improve the result as much as carbohydrates. Did you know that even tasting carbohydrates can improve your performance? Click here to watch the video.

Got it, carbohydrates are really important. So, what is the optimal amount of carbs for 6 hours of cycling? How much for an amateur race and how much for a pro?

It all depends on how many watts an individual produces during physical activity. To put it more simply, it depends on the intensity of the effort and our fitness level. 

For the vast majority of recreational cyclists it should be enough to ingest somewhere between 40 and 60 grams of carbohydrates per hour, but pro cyclists who compete at top level produce more watts and should ingest more carbs. 

Many athletes experience problems because the body is not used to so many carbs, or they are not consuming the right combination of carbs. 

“Around fifteen years ago at the University of Birmingham under the guidance of professor Asker Jeukendrup they were the first to discover that mixing both types of sugar leads to more efficient use of carbohydrates ingested during training. Participants ingested 90 grams of carbohydrates per hour either in the form of glucose or in the form of glucose and fructose in the ratio 2:1. With glucose the consumption of carbohydrates stopped at 60 g/h, but in the ratio 2:1 the consumption was much higher. The ratio 2:1 was created coincidentally and there was no reasonable scientific basis for it. And yet, it is today most often recommended as the optimal ratio.”

Tim, you are a cyclist yourself and surely there must have been moments when you had to retire from the race.

Although I’m a cyclist and I ride more than 20,000 kilometres each year, I only participated at two races in my life, and I completed both of them. It seems my body can take it all. Well, not all. I was piloting one of the studies in Birmingham and during physical activity they made me ingest a drink with a sugar called lactose, otherwise found in dairy products. I actually had to retire and spend a lot of time in the toilet. Being lactose intolerance can be a pain (laughs).

Image 2: Tim spends more time indoors than other cyclists - new discoveries are an additional motivation for training and races.

Why do so many cyclists experience digestive issues? Is it because of too aggressive aromas, inappropriate sources of carbohydrates, or something else? 

There are three main reasons for the development of digestive issues with cyclists.

The first one is that many athletes are not used to ingest carbohydrates during training. They think they are only reserved for competition.

The second reason is that for a long time they don’t ingest anything, then they become tired and try to compensate with a large intake. A large intake of carbs in a suboptimal combination of different types of sugars leads to digestive issues. We must know that carbohydrates, which soon break down into basic sugars glucose, fructose, and galactose, must absorb into the bloodstream. This is where specific transporters come in, but they have a limited capacity. There’s also the fact that glucose and fructose have different transporters. If we saturate the glucose transporters, we can still use the fructose transporters. This is why the ratio between glucose and fructose is very important.

The third reason is intestinal damage. This occurs mostly as a consequence of readjustment of blood from the digestive system into the skin and muscles. The best way to avoid this problem is by introducing enough liquid during physical activity. But don’t go overboard. 


Video 2: Digestive issues during training sessions are not caused by isotonic drinks or gels by themselves. The problem is in their incorrect ingredients - the unabsorbed amount during strain additionally irritates the sensible membrane of the digestive system.

Some people know the correct ratio between glucose and fructose is 2:1. I’m sure our readers would like to know more about this.

As already mentioned, we know three types of monosaccharides, which are the most basic form of carbohydrates. Relevant to us are only glucose and fructose. Nobody ingests galactose during physical activity, so we can forget about it. 

Most carbohydrates found on store shelves contain only glucose or chains of glucose. Bread, pasta, rice, maltodextrin – it’s all glucose. 

Then we have fructose, found in variable ratios in fruit and honey. As an interesting side note, table sugar sucrose is actually a molecule composed of glucose and fructose. Fructose is different from glucose not only in that it uses different transporters from the intestine into the blood, but it must first go to the liver and there transform into glucose or lactate. Maybe that’s why for a long time we didn’t consider it appropriate during physical activity. 

Around fifteen years ago at the University of Birmingham under the guidance of professor Asker Jeukendrup they were the first to discover that mixing both types of sugar leads to more efficient use of carbohydrates ingested during training. Participants ingested 90 grams of carbohydrates per hour either in the form of glucose or in the form of glucose and fructose in the ratio 2:1. With glucose the consumption of carbohydrates stopped at 60 g/h, but in the ratio 2:1 the consumption was much higher. The ratio 2:1 was created coincidentally and there was no reasonable scientific basis for it. And yet, it is today most often recommended as the optimal ratio.

But the story about the ratio does not end here. Professor David Rowlands from New Zealand discovered many years ago that the optimal ratio between glucose and fructose is quite different, namely somewhere between 1 unit of glucose and 1 to 0.7 unit of fructose. 

Why most people forget about his findings I do not know, but what I do know is that I did not forget (laughs). My slightly subjective opinion is that the optimal ratio is most likely 1:0.8 in favour of glucose. 

tuš team ndure

Image 3: Pro cyclists know that proper fuelling is crucial - members of the Tuš team are already testing the prototype of the new isotonic drink.

Didn’t they once claim that fructose causes fatty liver and is generally harmful to us?
We could talk about this for hours.
Yes, we hear many bad things about fructose. But the research is clear. If we are physically active and consume as much energy as we spend, fructose is not a problem. On the contrary - for athletes, as I just mentioned, it is recommended.
 
End of part 1. Read part  2 here
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