Marathon fueling (Read 2332 times)


Feeling the growl again

    Does anyone have a Trent-verified and endorsed figure on how quickly simple carbs (okay, sugar) become available to the muscles?  Not much point in a Gu at mile 20 if it doesn't reach your muscles for another hour.  Actually, I bet Spaniel has a pretty good handle on this.

     

    No time to do a Trent-quality search and this was harder to find than I thought...

     

    About two paragraphs under the glucose molecule.

     

    So something like a 100cal Gu, made primarily of simple sugar, will indeed be in your system within a mile or two.  More complex forms take substantially longer.  This source implies 15X as long, that seems somewhat excessive and I doubt it is linear.  So that Gu at Mile 20 will probably give you a lift through the line, but a piece of bread won't.

    "If you want to be a bad a$s, then do what a bad a$s does.  There's your pep talk for today.  Go Run." -- Slo_Hand

     

      Free lectures on iTunes on some of this stuff.

       

      There seem to be two different sets of lecture recordings for the same class, Physiology of Exercise. The ones I originally found and listen to on my iPad are from Fall-2009. Those linked above on iTunes are from Spring 2011. Not sure what the difference is.

      Failure is a good start.

        No time to do a Trent-quality search and this was harder to find than I thought...

         

        About two paragraphs under the glucose molecule.

         

        So something like a 100cal Gu, made primarily of simple sugar, will indeed be in your system within a mile or two.  More complex forms take substantially longer.  This source implies 15X as long, that seems somewhat excessive and I doubt it is linear.  So that Gu at Mile 20 will probably give you a lift through the line, but a piece of bread won't.

         

        Thanks...and, once it's in the blood, the muscles can immediately use it, or is there another stage for conversion to glycogen?

         

        Yeah, I suppose I can start googling this.

        Well at least someone here is making relevance to the subject.

        Stacks


          Two things.  (And let me say I am not a medical professional -- I just play one on the internet.)

           

          As I understand it, when you have glucose in the bloodstream it is available for the muscles to use.  Glycogen is something your body makes from glucose in order to store it for later, and only gets made when there is surplus glucose flying around.  So I would think in the ordinary course that if your body needed glucose as it was being made available, some if not most would be consumed by the running, with the balance being banked as glycogen for later.  If I am right, I don't think you need to build extra time in for conversion to glycogen.

           

          However, I gather that digestion is an energy-intensive activity, with high demands for oxygen.  When you are involved in high-output activities, I think that your muscles will compete with your digestion for oxygen, and this may slow things down and increase the amount of time it takes for the Gu to get to where you need it.

           

          References:  Something I read somewhere.

          Scout7


          CPT Curmudgeon

            Another thing to keep in mind is that the brain uses glucose for fuel as well.  However, it is unable to store its own supply, so it relies on supplies from the liver, which is transmitted through the blood stream.  Which could be why there's a boost simply from tasting something sweet, as the brain thinks fuel is on its way.

             

            All that being said, in the end, it really doesn't matter a whole lot.


            Feeling the growl again

              Two things.  (And let me say I am not a medical professional -- I just play one on the internet.)

               

              As I understand it, when you have glucose in the bloodstream it is available for the muscles to use.  Glycogen is something your body makes from glucose in order to store it for later, and only gets made when there is surplus glucose flying around.  So I would think in the ordinary course that if your body needed glucose as it was being made available, some if not most would be consumed by the running, with the balance being banked as glycogen for later.  If I am right, I don't think you need to build extra time in for conversion to glycogen.

               

              However, I gather that digestion is an energy-intensive activity, with high demands for oxygen.  When you are involved in high-output activities, I think that your muscles will compete with your digestion for oxygen, and this may slow things down and increase the amount of time it takes for the Gu to get to where you need it.

               

              References:  Something I read somewhere.

               

              All glycogen is is a polymer of glucose.  A bunch of glucose molecules hooked end-to-end.  This is why it's pretty accessible, enzymes just need to clip it apart.  Unlike fat and protein, which both much be more extensively altered to get back to forms that can directly be processed for energy.

               

              I would not say digestion is energy-intensive, unless you are eating celery it is a net energy gain for you.  But it requires blood supply to carry the nutrients away, and there it does compete with running because your blood is being diverted from your gut to your working muscles.  Working muscles use WAY more oxygen than digestion does.

              "If you want to be a bad a$s, then do what a bad a$s does.  There's your pep talk for today.  Go Run." -- Slo_Hand

               


              Feeling the growl again

                Another thing to keep in mind is that the brain uses glucose for fuel as well.  However, it is unable to store its own supply, so it relies on supplies from the liver, which is transmitted through the blood stream.  Which could be why there's a boost simply from tasting something sweet, as the brain thinks fuel is on its way.

                 

                All that being said, in the end, it really doesn't matter a whole lot.

                 

                This is why true bonks really suck.  Your brain can't work right.  No training benefit to that.

                "If you want to be a bad a$s, then do what a bad a$s does.  There's your pep talk for today.  Go Run." -- Slo_Hand

                 


                old woman w/hobby

                  Thanks for responses. Did 17 miles today. Easy run. Garmin keep beeping for me to slow down. Smile

                  3- 8 miles 9:04 -10:07   9-16 miles 8:07 - 9:50. Feeling good. Decide to do  hilly course  the last 5 miles.

                   

                  Mile 4 was 10:50 because some ahole hit me with a cup of  soda. Did not get a tag number.

                   

                  Run with the hydration pack. Will not use it for the race.  It was more annoying  than the benefits it would give.Will carry a hand held.

                   

                  Tent is correct. I should have posted marathon fueling / hydration.

                   

                  St Charles ,IL  45 miles west of Chicago.  Average weather 48 -72. Last year 53 -66. Sept 18.

                    stupid pig.

                  steph  

                   

                  OCD  If you don't laugh...   

                    Runners run.


                    HobbyJogger & HobbyRacer

                      I just about never fuel during long runs b/c I am too lazy to mess with it. I drink sometimes, especially if it's above say 85F, and especially if it's also sunny.    As far as I can tell from observing people with whom I run, fueling and hydration vary a lot from person to person.

                      It's a 5k. It hurt like hell...then I tried to pick it up. The end.

                        From Mcmillan, for those who havent seen this before: Click . Read the entire article all the way to the bottom. I am posting an excerpt here.

                         

                        From what i have read, i believe bonking (or something just short of that) once in a while during training is necessary to get a good fix on your limits so that you can work around that the next time you run. Repeatedly bonking of course is of no use whatsoever.

                         

                        Email:

                        Greg,
                        I am dietitian and a competitive marathoner. I was reading your website about nutrition and was interested in the portion about withholding carbohydrates during long, steady runs. Do you know of any research studies that have studied this?

                        Thank you.

                        My reply:

                        Thank you for your email. Unfortunately, to my knowledge there doesn't appear to be any research on this specific topic, only cursory research. There is research showing that a consistently low carbohydrate diet impedes performance but that is for day after day of carbohydrate restriction - not what the article proposes. There is also research showing that carbohydrate intake before and during exercise improves performance in that exercise bout but again, this isn't what the article talks about. In this strategy, we are only restricting carbohydrates on one type of run and that is only once every other week during a marathon cycle. I want to know why this strategy works. Is it metabolic or mental or some other factor that we can't yet measure?
                        My research questions are:

                        1) If a runner follows all the usual nutritional advice but uses this strategy on long, steady runs, is there a greater usage of muscle glycogen stores (thus getting glycogen depleted quicker) versus someone ingesting carbohydrate before and during the same long run? I would be interested in the results from each particular long run as well as across a marathon training cycle.

                        2) For the same runner, is the amount of intramuscular triglyceride (this is the fat stored within the muscle cells and is the fat we hope to increase the use of) used different than with the usual carbohydrate ingestion? (Again, per run and across a training cycle.)

                        3) Can a runner using this strategy better tolerate lowered blood glucose after this strategy? Since we know that a large part of fatigue in the marathon is due to lowered blood glucose, is this the mechanism that makes this strategy successful? In other words, runners who can better tolerate lowered blood glucose perform better in situations when blood glucose becomes low (like at the end of the marathon).

                        4) Is there a greater post-run replenishment of glycogen and triglyceride storage with this strategy? This would better equip the runner for future workouts and races.

                        5) Is there some other mechanism besides fuel usage that makes this strategy successful? (mental/placebo effect, enzymatic, muscular resistance to micro trauma, etc.) In the scientific world, we often forget that new technology often leads to breakthroughs in understanding nature. We're arrogant and say, "You can't prove it so it isn't true." That's a limited view. We must always be prepared to say that something else may be going on that we don't have the technology or intellectual breakthrough to measure. And lastly, statistics as required in science is not precise enough or can't discern enough to really tell us "truth" as some people suggest science provides. Using statistics, it's not possible to say why the person who won the 100 meter dash in the Olympics actually won. Each runner (given that the sample size is only 8) was just as good statistically as the next but yet, we gave out a winner's medal. There are things that come together in the body to produce a superior performance that I doubt the laboratory will ever be able to tease out just exactly what works and what doesn't.

                        6) Is this strategy scientifically successful? I've been using this strategy with athletes of all ability levels and it works in ~85-90% of them. Some athletes are simply too carbohydrate dependent to tolerate this strategy - kind of like responders and non-responders to altitude training. For some runners, it just doesn't work. But, for the majority of runners, reducing their dependence on carbohydrates before and during exercise, appears to provide a boost in performance. I see quicker than anticipated fitness gains across the training cycle which leads to great performance improvements than expected. NOTE: Some athletes have to go very slow in their reduction in carbohydrate use on long, steady runs whereas other can go cold-turkey.

                        7) Why does this strategy work in the majority of athletes but there are a handful of non-responders?

                        8) I've worked with a lot of international athletes from cultures with diets having less refined sugars. This strategy came from observing them as well as from talking with coaches and athletes from the 60s and 70s. Is it simply that the American diet is so heavy in refined sugar that we've lost the ability to tolerate temporary low blood glucose? Or, are we just so used to never being hungry (low blood glucose, lowered energy stores and altered hormonal states) that we don't know that we can still perform in endurance events much less sit at our computers and push paper without a constant flow of blood sugar? Energy drinks and energy gels are relatively new yet folks ran very fast back before these were so available for training and racing (not discounting the use by the elites of sodas, teas, etc.) but the average Joe runner certainly had much less carbohydrate during exercise yet still ran well.

                        9) Lastly, is it sufficient to just reduce carbohydrate use during exercise or does it have to be before and during? Is the mechanism for success simply that training is supposed to fatigue us and only through fatigue do we get a training stimulus so doing things to facilitate fatigue in different types of workouts is helping to increase adaptations to training? In other words, is it like hill training. Hills require more effor than flat running so we seek out hills to provide more fatigue than running on the flats. Using this strategy, we are inducing more fatigue, sooner in the run, thereby getting more of a training stimulus than by maintaining a constant blood glucose level using external sources like sports drinks and gels.

                        Most of the research has been set up to measure the effects of a nutritional intervention on a single performance bout. But this is easy science and we all know from practical as well as scientific study that we must have carbohydrate to improve endurance performance. The article doesn't argue this. It simply reveals an infrequent training strategy that is proving to improve event performance. Curious stuff and I'd like to hear your insights.

                        My current thinking is that it simply is a way to get quicker and deeper fatigue during certain runs which enhances the physical adaptations from that run as well as exposure to the mental 'feelings' that accompany this fatigue so that during the event, the athlete can tolerate fatigue better.

                        Cheers,

                        Greg

                        I dont sweat. I ooze liquid awesome.

                          Nowhere in that article does he talk about bonking being beneficial. Obviously (I think) getting the body used to some level of glycogen depletion is helpful in specifically training for the marathon. Maybe you have a different definition of bonking, but as I understand it, that's when you run out of glycogen to the point where you are running with the reptilian brain, which is to say, hardly running at all.

                            Obviously (I think) getting the body used to some level of glycogen depletion is helpful in specifically training for the marathon.

                             

                            Perhaps i should have called out "...bonking (or something short of that)..." a little more. As you say, I agree that you need to get used to some level of glycogen depletion - what i meant is, in trying to do that, its possible that you may bonk or to put it in a better way, find your tipping point. So that serves as a yardstick for your next run to avoid system shutdown by making some subtle changes to your run ... perhaps have some carb intake a couple of miles earlier, reduce effort etc etc.

                            I dont sweat. I ooze liquid awesome.


                            A Dance with Monkeys

                              Does anyone have a Trent-verified and endorsed figure on how quickly simple carbs (okay, sugar) become available to the muscles?  Not much point in a Gu at mile 20 if it doesn't reach your muscles for another hour.  Actually, I bet Spaniel has a pretty good handle on this.

                               

                              It is unpredictable.  Especially for a body in extremis. 


                              A Dance with Monkeys

                                A true glycogen bonk, when your body totally runs out of the energy sources required to operate its most basic functions. Everything goes dark. Like a long heavy tunnel collapsing around you. All you want to do is lay down and die, except you can barely even process that want. You may see flashing lights, or bright rings, or just that deafening darkness. It is unlike just about any other experience. It would be scary, except you don't even have the strength to experience fear.