embracing the theory that you start out a race with some amount of stored calories,
and you consume so many calories from gels, drinks and energy bars during the race
trying to keep up with your losses… (in a long race, like IM)
your theoretical stored calories deficit usually increases (because you are limited by the amount you can swallow and your body can digest)
so we can calculate/approximate your approximate theoretical balance/deficit at any point during the race.
my question is: at what deficit do you bonk/hit the wall? obviously you don’t have to finish the race with a 0 balance…
you can finish with some deficit, but which deficit amount should you stay above?
(i know there are “individual differences” arguments… assume the average athlete… )
I don’t think it would be possible to define how many calories you can be down to bonk since that would depend on how much and at what intensity you are exercising.
I think a better question would be is what your blood sugar levels would be for you to bonk. That’s something I’d be interested in getting one of those blood glucose meters that diabetics use to find out.
Yeah, agree here…to layer on a bit more logic (though I’m not a science-guy, so take this with a grain of salt), I think this would be almost impossible to measure or even define an “average” because intensity of the activity matters so much. For example, I may be working at 80% of my max, and burning through carbohydrates (whatever stored, and then the 300 I put down in Gels and Sports-drink every hour) but once I start to run a deficit, what if I lower my exertion and now start using fat for fuel. I might be able to avoid the “bonk” or “wall,” but at the same time, I will have to slow down to do so.
Maybe if you operated under the assumption that an athlete is going to be maintaining an intensity above the fat-burning zone, then you could drive toward a better representative answer, but even then, there is going to be a lot of variability around what that exertion level means for unique individuals.
This Article says that a trained individual can store up to almost 900 grams of carbs, so from a caloric standpoint, that is 900x4 or 3,600. I find that hard to believe, since if that was the case, there would be no need to take down any calories in a race lasting under 3.5 hours (assuming a high burn rate of 1000 calories per hour). But, using that logic, if you figured out your stores, then layered on your 300-400 calories per hour, and figured out at what point you bonked, you could get an answer, though not sure I would want to sacrifice my training for this experiment. Bonking is no fun, and takes a while to bounce back from.
This Article says that a trained individual can store up to almost 900 grams of carbs, so from a caloric standpoint, that is 900x4 or 3,600. I find that hard to believe, since if that was the case, there would be no need to take down any calories in a race lasting under 3.5 hours (assuming a high burn rate of 1000 calories per hour).
900 sounds high - I’ve read more like 500g, but in any case, muscle glycogen is useable only in the muscle in which it is stored. Only liver glycogen, released into the blood as glucose, is transferrable to working muscle.
Even if you were to lower your ‘exertion rate,’ you never stop burning carbs. Also, you will always burn more carbs than fat, there is just a different percentage. What you were referring to as the ‘fat-burning zone’ is really just where the ratio of carbs burned to fat burned is closer to one. (You would have to be at 50% vo2 max to be burning 3:2, carbs:fat… basically a fast walk). Eventually you would hit the wall, regardless of how much you slowed down.
As for the whole lasting 3.5hrs bit, JollyRodgers got that.
Eventually you would hit the wall, regardless of how much you slowed down.
exactly, and i’m wondering what is that “eventually”? i don’t think it’s a balance of zero carbs calories.
i think you can be in a substantial negative
and still not hit the wall. assuming that’s true, how do you explain that? anyway, approximately at what deficit do you people think you hit the wall? i mean, people who have hit the wall can probably estimate based on what they have taken in during a marathon for example…
you will always burn more carbs than fat, there is just a different percentage.
The information I’ve seen, e.g. Edwards HT, Metabolic rate, blood sugar and utilization of carbohydrate. Am J Physiol 1934, shows a near linear decrease in CHO utilization along with a corresponding increase in fat utilization as a function of exercise duration. In their study CHO > Fat for periods less than three hours and CHO < Fat for longer periods.
This image, presumably at a higher intensity, shows a much lower threshold.
This graph shows Fat% > CHO% for low intensities, e.g. < 40% of max.
approximately at what deficit do you people think you hit the wall?
If you’ve got some time I think you’ll find that information in this paper will answer most of your questions: Metabolic Factors Limiting Performance in Marathon Runners
I’d also encourage you to try the Running Endurance Calculator site to learn more about the relationship between CHO loading, ingestion and marathon performance.
it may be the wrong question to ask, it doesnt really matter much what you ate the days before, the morning, and during the workout/race etc, all that matters is, if you start out too fast, you will be slow at the finish or possibly bonk, you cant eat your way out of a future bonk at mile 22 of a marathon or something like that if you ran the early miles too fast,
.
it may be the wrong question to ask, it doesnt really matter much what you ate the days before, the morning, and during the workout/race etc, all that matters is, if you start out too fast, you will be slow at the finish or possibly bonk, you cant eat your way out of a future bonk at mile 22 of a marathon or something like that if you ran the early miles too fast,
that’s an interesting fresh new hypothesis. on what do you base it? or is it just your opinion?
you will always burn more carbs than fat, there is just a different percentage.
The information I’ve seen, e.g. Edwards HT, Metabolic rate, blood sugar and utilization of carbohydrate. Am J Physiol 1934, shows a near linear decrease in CHO utilization along with a corresponding increase in fat utilization as a function of exercise duration. In their study CHO > Fat for periods less than three hours and CHO < Fat for longer periods.
This image, presumably at a higher intensity, shows a much lower threshold.
This graph shows Fat% > CHO% for low intensities, e.g. < 40% of max.
a study from 1934? did they even have the means to measure anything back then?
anyway, i don’t get the answer from these graphs. help please
And that just gets back to the blood sugar issue, once it gets past a certain you will have to slow down…or pass out.
That’s true, but your body will maintain blood glucose for a while after you run out of muscle glycogen–the liver stores some glycogen as well. So at least in theory, you’ll know you’re bonking before your blood sugar starts to tank and you start passing out, having seizures, getting hypothermic, and what not.
Yes, I agree but I would assume that the liver glycogen would be used up to a point that the brain would start slowing things down to save the sugar for itself, so I suppose I exaggerated on that.
I kind of subscribe to the central governor theory on that but I do believe that some (very few) people have the ability to push near the point of passing out, those would be people at a very high level.
I’m sure there are people who tolerate hypoglycemia better than others, but as athletic performance goes I think an athlete’s performance would fall off enough to knock them out of the event before their tolerance of hypoglycemia made any difference. But that’s all educated guessing–an exercise physiologist I’m not.
it may be the wrong question to ask, it doesnt really matter much what you ate the days before, the morning, and during the workout/race etc, all that matters is, if you start out too fast, you will be slow at the finish or possibly bonk, you cant eat your way out of a future bonk at mile 22 of a marathon or something like that if you ran the early miles too fast,
that’s an interesting fresh new hypothesis. on what do you base it? or is it just your opinion?
take a marathon for example, if you are in shape for a 3:00 marathon, you you do the first 10 miles or so at 2:45 pace, you are likely going to bonk around mile 20, and no amount of eating is going to stop that
embracing the theory that you start out a race with some amount of stored calories,
and you consume so many calories from gels, drinks and energy bars during the race
trying to keep up with your losses… (in a long race, like IM)
your theoretical stored calories deficit usually increases (because you are limited by the amount you can swallow and your body can digest)
so we can calculate/approximate your approximate theoretical balance/deficit at any point during the race.
my question is: at what deficit do you bonk/hit the wall? obviously you don’t have to finish the race with a 0 balance…
you can finish with some deficit, but which deficit amount should you stay above?
(i know there are “individual differences” arguments… assume the average athlete… )
Not sure this answers your question but this is my experience from someone who supposedly burns a lot from fat. I am considered diabetic, but I do not take medicine, insulin…I just control it by diet and excercise. I do test my blood sugars to know what is going on.
I did Florida 70.3 on 290 calories total in just under 5 hours, so that is 60 calories per hour. I tested my blood sugar at the end and I was not at the point of a bonk.
I did Vegas 70.3 on 373 calories, but felt I was pretty close to a bonk. The heat probably didn’t help.
Assuming I was burning about 700 calories per hour, I had a deficit of 640 per hour.
At the end of 5 hours I was close to empty
I know because of my diet and training habits (mostly diet) I do burn higher percentages of fat than most.
So I would say I could take about 3200 calories, dlivide it by the number of hours I plan to race and that would be my acceptable calories per hour deficit.
did they even have the means to measure anything back then?