Taking gels during training runs

markeroon said: So Cotton Shirt, here V02 is correlated with pace, right? The general idea being that if your V02 is higher then you'll be running faster and thus burning calories at a faster rate?

dependent always on your definition of "general idea."

there seems to be general agreement that the folk at the front of the marathon have, generally, higher VO2 max than the folk farther back. but it is also unsafe to assume that everyone in front of you has a higher VO2 max than you. in other words, taking the population as a whole, statistically, you need a high VO2 max to run a fast marathon, but when we look at individuals, having a high VO2 max does not guarantee that you will run faster than other folks. there are many counter-examples to demonstrate this.

therefore, I choose to interpret the calculation as saying that the guys with the high VO2 max are consuming more oxygen per minute, and they are burning glycogen faster in order to do that, and whether they actually convert that into a faster race will depend on a lot of other factors. broadly speaking you can assume that, but it is not a given.

it is important, I think, to remember that this is a calculation of energy expenditure and endurance, not necessarily of performance. the point of this exercise was to demonstrate that no one "needs" gels to complete a marathon unless they are undertrained for the event. it doesn't claim to show that a man who weighs x and has a VO2 max of y can run a marathon in time t.

cheers.

Thanks for the explanation. I don't have the Lore of Running with me right now, but I'll check it when I get home. I do note, however, that your calculation (and Noakes's, I presume) takes a different path than Rappaport's work, with different outcomes. For example, Rappaport seems to take into account that different body sizes can store different amounts of glycogen. Your weight estimate for a 2:20 marathoner (172 lbs) strikes me as a bit on the high side. I'm not saying it's impossible , just unusual. Rappaport's model includes the possibility you mention that training and carb loading can make in-race fueling unnecessary for some runners, but a more likely outcome is hitting the wall at 18-25 miles.

As for the physiology, see the recent review article of Burke et al., Science 362, 781-87 (782), also available online: "Strong evidence suggests that performance in a range of sports and exercise scenarios is enhanced by consuming CHO during exercise, with intakes targeted to the muscle’s need to supplement its diminishing glycogen reserves [30 to 60 g/hour in endurance events of up to 2 to 3 hours duration and 60 to 90 g/hour in ultra-endurance events lasting 8 to 10 hours (10)]. "

A popular article on Rappaport's model is here:

It seems, generally speaking, that gels aren't needed to provide fuel (carbs) to complete a marathon and that having extra carbs from gels won't improve performance. What if you are a heavy sweater and the gels you consume provide electrolytes you lose from sweat? Wouldn't this be a valid reason to consume gels during a marathon? Yes I suppose you could drink Gatorade if it's offered, but if you have a gel that provides electrolytes and agrees with your stomach it seems this would be an important reason to consume gels for someone with a high sweat rate?

You're not going to run into glycogen depletion on a 20-22 mile easy paced long run if you've been training properly, so taking gel shouldn't give you much if any boost. Even at race pace it usually takes at least 18 miles to hit the wall. I would recommend experimenting with sports drinks or gels on at least one long, fast paced run just to see what your stomach can tolerate, though. Even if you're perfectly trained and carbo loaded before the race you'll be on the cusp of running out of glycogen by the end, so taking in some carbs during the race could be what gets you over the top.

I don’t have the link at the moment, but Kipchoge used a combo of gels and drinks to hit the magic 90g per hour of carbohydrates.

You don’t need to educate us on nutrition. Plenty of people on here, myself included, are more educated and accomplished than you and used modern day gels to succeed.

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slow guy here wrote:

2:50's hobby jogger here but I only do gels on my longer training training runs 20+ miles. I'll only take 3. then for the actual marathon ill take 5 or 6.

Exactly. Practice during a few long runs. But avoid taking gel or sports drink for any run under 15 miles.

my 2c said: Thanks for the explanation. I don't have the Lore of Running with me right now, but I'll check it when I get home. I do note, however, that your calculation (and Noakes's, I presume) takes a different path than Rappaport's work...

from your comment it seems that you have not read the entire answer to your question. I think you need to keep reading until you get to the end.

as for Rapoport, he is calculating something different and comparing his work with my explanation of why you do not need gels is not really comparing apples with apples. if you had read the whole answer I think you would have got this.

cheers.

I've now had a chance to look at Noakes. Thanks for the reference. First, I'm sorry for saying the basic physiology wasn't on your side. I just finished reading Endure by Alex Hutchinson, and I should have remembered that there's currently no agreement on what causes fatigue. Basic physiology has yet to choose a side, it seems.Noakes, though, isn't on your side. From p. 150, under "Carbohydrate Ingestion During Exercise":

Only recently have studies established that the ingestion of carbohydrate during prolonged exercise not only reduces the perception of fatigue...but also delays fatigue and enhances performance.... Carbohydrate should be ingested throughout exercise.

Noakes goes on to cite studies showing performance enhancement in races as short as 15 km or 50 minutes.

Even assuming your math is sound, you're assuming that muscle glycogen depletion is what leads to hitting the wall in a marathon, when it could be something else (depleted liver glycogen causing the Central Governor to panic) or a combination of things. The jury on that is still out, so we're not yet at the stage of using math to prove that taking gels is useless.

If you maintain that taking gels is useless, however, you will need to come up with an explanation for both the experimental evidence and many athletes' experience. Taking gel or drinking carbs comes at a significant metabolic cost, in that your body has to divert blood and resources from the muscles to the digestive system to do anything with the carbs in your gut. If those carbs were of no use and were actually a waste of resources, we'd predict that the top elites would gain a significant performance edge by avoiding them. That doesn't seem to be what the elites are currently doing, however. (Although, interestingly, there are exceptions to this, so it's possible that the boost from carbs may not always be worth the metabolic cost.)

my 2c Even assuming your math is sound, you're assuming that muscle glycogen depletion is what leads to hitting the wall in a marathon ...

I haven't made that assumption at all.

I never said one word about hitting the wall.

all I have done is reproduce Noake's maths to show that energy is not exhausted after time t.

if you want to interpret that as meaning anything else then you are on your own.

If you maintain that taking gels is useless...

I didn't say that, either.

I said that you don't need to take them. you don't need to eat an orange, that doesn't mean that oranges are useless.

I do maintain that gels are merely expensive sugar with flavouring added and that if you want to eat something during a run there are cheaper alternatives. and I maintain that if you cannot run twenty five miles without needing something to eat then you are undertrained for that event. and I think the maths I have presented shows that quite clearly.

nothing you have said contradicts that.

cheers.

Problem is, it's not about 'can you run x miles without needing to eat y'. It's about performance over distance. V02 _max_ drops off over distance, especially over 5k, even more especially at marathon distance. So you can't use vo2 max in any sensible way like you have in your calculations unless you want to start including calculus (there may be a simpler equation, but I'm not aware of it). You need to quit that elementary school math.

I agree there are cheaper alternatives, and no reason why someone shouldn't use any simple substitute.

If you want to say 'gels are a myth' in terms if can you hit a distance I agree.

If you want to say 'gels are a myth' in terms of speed, I agree.

If you want to say 'gels are a myth' in terms of distance / speed, you are talking rubbish.

Trying to claim there's a difference between hitting the wall and exhausting energy in a marathon is playing coy. It's unfortunate you're not making an effort to hold a conversation, but you do you. Here's what you did say:

gels are a myth

Your original example was quite odd by choosing a 2:20 marathoner with a relatively high weight of 78 kg and with a vO2max of 48, which is quite low and would require the athlete to have extraordinary economy. If you start with a more likely 2:20 athlete - 68 kg and vO2max of 70 - and plug in the numbers, you would find, by your own math, that the runner exhausts his glycogen supply at 122.4 minutes, or over 3 miles from the finish line - not an unheard of time for a marathoner to slow significantly. (Also, note that Noakes doesn't use vO2max in his calculation; he starts with an average economy of 67 ml O2/kg/min instead.) Using Noakes's math, that fit 68 kg marathoner would have to drop to 62 kg - from 149.6 to 136.4 lbs - to extend the goal finishing time to 140 minutes, if there is that much weight for a 2:20 marathoner to lose in the first place.

So if you think gels are a myth, I'm not sure what your example was trying to show, since your math seems to clearly describe a fairly common class of well-trained marathoner whose glycogen supply will run out before the end of the race, and who would benefit from carbohydrate intake, as experiments and the experience of many athletes suggest.

my 2c said: blah blah blah

I would like to remind you that this conversation started because you asked me to explain why I believe what I believe about gels. as far as I am concerned all I have tried to do is convey to the best of my ability, the answer to that specific question. i have explained why I believe what I believe.

if you're not convinced, okay. that's fine.

cheers.

actually I have decided that it's not fine, because you are making a very basic and annoyingly common mistake. in practically the first thread I commented in on this forum Smoove made this mistake, then later in the same thread 800 dude made exactly the same mistake, and in the intervening couple of years lots of others have made the mistake and more recently Rojo made it and now you are making it. the mistake goes like this: 1. make an assumption 2. decide that your assumption does not make much sense 3. criticise me for this assumption you made at this point you are probably convinced you haven't done this and I'm just making it up. so here is you doing exactly this...

Your original example was quite odd by choosing a 2:20 marathoner with a relatively high weight of 78 kg and with a vO2max of 48...

1. you assume that 78kg represents the weight of a 2:20 marathon runner

2. you decide that 78kg does not represent the weight of a 2:20 marathon runner

3. you criticise me for this assumption you made

I do, frankly, struggle to understand why this three-step process needs to be explained to you in such microscopic detail, I struggle to understand how people who think like this survive into adulthood, I fail to understand how you can have the bare faced cheek to come one here with, "you be you," and calling me "coy" when you self-evidently have the thought process of a nine-year-old child. this is not just intellectual gibberish it is, frankly, dishonest.

you started this conversation by complimenting me for my thinking, you said that my ideas were, "generally well thought out," and yet you think you can refute my "well thought out" ideas with this foolish gibberish. if that is what you think intellectual debate is about then you are going to be disappointed on a very regular basis.

as should be patently obvious, 78kg does not represent the weight of a 2:20 marathon runner. the technical name for 78kg in that context is an example. it is there to show you how the maths works.

now try thinking for yourself.

cheers.

I ran a 3:08 marathon and did not eat or drink anything during the race. After the race, I was throwing up part of a doughnut I had eaten about an hour before the race. I ran 7 minute pace for 18 miles and 7:30 pace for 8.2. Was I bonking or was 35 mpw not enough miles for a marathon.

This tells me that at a certain effort, I am not able to process food. If I took a gel or gels during the race, would I be able to convert them to energy or would they just sit in my stomach and upset it?

I do know I can eat if I run at a pace slow enough because I have done 65 miles and was definitely able to convert the food I ate to energy.

If you look at McMillan calculator, you will see that the difference in pace between a 20 mile race and a marathon is only 8 seconds per mile. I suspect the "wall" is caused more by running the first part of the race at a faster pace than you are capable to complete the race at.

cotton shirt, if everyone keeps misunderstanding you, maybe the problem is you? Smoove is one of the most knowledgeable and patient posters here. He wouldn't be anywhere in the first 1000 posters I'd name if I had to name annoying posters. It is worth revisiting one point, I think. You write:

as should be patently obvious, 78kg does not represent the weight of a 2:20 marathon runner.

But this is not obvious at all. Take a look back at your original example:

start with your weight in kilograms. (78.0)

multiply by your VO2 max (78.0 x 48 = 3744.0)

divide by 1000 to give you the litres of oxygen you consume per minute. (3744.0 / 1000 = 3.744)

multiply by 20, because each Litre of oxygen produces 20 kJ of energy. (3.744 x 20 = 74.88)

divide by 16.65, the number of kJ per gram of carbohydrate. (74.88 / 16.65 = 4.4972)

this gives you the number of grams of carbohydrate you burn per minute, at VO2 max. (4.4972)

then divide 700g (the average glycogen stored in your muscles) by the above figure to give you your endurance in minutes. 700 / 4.4972 = 155.6524 minutes = 2:35:39, over two and a half hours or more than 15 minutes longer than his marathon will take. therefore, he does not require extra fuel.

Notice the bolded lines. Your example starts with a 78 kg marathoner, proceeds through a series of calculations based on that weight, and ends with a 2:20 marathon. Do you see yet why I'm assuming from your example that the 2:20 marathoner in your example weighs 78 kg?

It's perfectly normal to point out unwarranted assumptions. That's what I hope a conversation will lead to, and in the end what had seemed confusing might become clear. It's quite possible to reach that outcome without referring to questions and counter-points as "foolish gibberish," actually.

I really do appreciate the reference to Noakes. Working through the calculations was interesting. I learned something. It's really too bad that you prefer not to consider why so many elite marathoners keep guzzling carbs; or why sports scientists like Noakes keep recommending it and experimentally verifying its efficacy; or the implications of working through your calculations with a slightly different set of starting parameters and arriving at the opposite outcome.

this is a completely fair point.

I had not intended that to be taken literally as an example of a 2:20 runner. they were just some numbers as an example of how the maths works. once you know how to do the maths we can move on to other examples...

can I assume, then, that you have not yet read the posts in which I did exactly that?

I showed examples of runners at three different weights, at three different VO2 max and with different amounts of starting glycogen reserve. but you don't seem have seen these and have not so far referred to them.

what was that you said about unwarranted assumptions? I have considered it, and I also think that the point of thinking about these topics is to examine whether the status quo needs to be challenged. we do not just keep doing something because we have always done it, and the mere fact that folk do something does not, in and of itself, mean that we should do it or that we need to do it. there is also the fact that I don't really know what any specific elite puts in their drinks. we might assume that they put electrolytes or salt or atomised sunlight or some secret blend of eleven herbs and spices in there but does anyone actually know what is in those water bottles? if this is simply a case of, "your guess is as good as mine," then what, exactly, are we considering?

cheers.

Thanks for the mea culpa on the original post.

But isn't that calculation a little flawed - I am assuming that the calc shows complete exhaustion of stored glycogen for someone operating at VO2 max.

But using that to show how long you can go in a marathon without additional fuel is surely flawed because:-

- operating to exhaust all glycogen is too unrealistic

- marathons are not run at VO2 max, but at substantially less than that

My personal experience

My best executed marathon race, where the outcome was in line with the training prior to it, was conducted based on a gel strategy. Not because I thought it was absolutely essential, but because it was convenient and reduced the risk of complete depletion over a 3hr15 race (aged 45, 72kg and only a moderate amount of natural talent).

My approach was to fuel well in the morning, as you'd expect. And then to consume 1 gel of 22.6g carb every 25 minutes / 3 miles from the start. At that point my gut was completely able to process the carbs effectively, as my system was not stressed. As I progressed through the race, my system got more stressed to the point at which I took my final gel at 18 miles (so 6 consumed) as I felt I would cause myself GI issues if I took another one. Plus, with only 8 miles to go AND 6x gels in my gut of which most of which had been processed fairly normally, I should not have needed any more.

It worked for me, and even it it was completely unnecessary, all that happened to me was that I consumed 6 gels and wasted some cash. An appropriate sacrifice! And one that I'd repeat as it worked - I've not got the time to experiment with finding out how much i really needed them!

A 2:20 marathoner certainly has a higher VO2 max than 48.