1

Carb loading (Read 731 times)

    What is it? How does it work? When do you start? And, how many additional carbs are typically required? Would love to hear some specific strategies currently in use by some of the more seasoned runners in this forum. And, it would be great if you would mention different plans for different distance goals (10k, half marathon, marathon, etc.)


    A Dance with Monkeys

      Carb loading is really for the marathon. It is not helpful when running less than about 20 miles. Here is why, from a prior post - The human body can contain a maximum of about 2000 calories of stored glycogen. Glycogen is the energy source we use when we run. Your body stores glycogen in the muscles and in the liver. Most of us burn about 110-140 calories for every mile we run, which means we will run out of glycogen after about 16-18 miles if we are burning only glycogen (we are not, see below). After you run out of glycogen, your body will force you to stop as you transition from burning glycogen to burning protein (i.e., your leg muscles). Once your body has transitioned, you can run again. In part, it is because of this protein burning that your legs hurt for days afterwards and you require recovery before you can run again (that and the lactic acid buildup, etc). It is for this reason that many runners can go 16 miles casually, but require planning and extra effort to go beyond 20. Taking in calories during the run can extend this by preserving some of the (liver) glycogen. A packet of gu-stuff has about 100 calories (worth just under a mile of running) and a 4 ounce cup of gatorade has about 8 calories (about 50-100 yards). Even if you take in 8-10 gu packets during your run (yech, blech, eeeww, uch) you will not necessarily absorb all those calories efficiently, so you still are likely to run out. In general, the more you run in your life, the more efficient you get at burning glycogen. People who have run distance for years, and who put in 40-60+ miles per week use and replace glycogen more efficiently than folks who have only been running for a short time and who can only put in 20-30 miles per week or less. The more efficiently you burn glycogen, the less quickly you use it up, and the further you can go. Your body simply cannot store more than about 2000. Once you got to 2000 (or whatever YOUR body can hold) you will not store more. You burn glycogen all the time, whether running or not. If you were to sit at your desk all day doing nothing but surfing this board, you would still burn about 1500-1800 calories / 24 hours (although you probably burn a little more than that just by having muscles trained to run a marathon), and so all you are doing is repleting that when you carb load up every next day. When you wake up the morning of a long run or a marathon, you have already lost several hundred calories from your glycogen stores just by breathing and sleeping the night before. More if you were nervous. That is why your breakfast really counts as your carb loading unless done right before the run. If you finished dinner and went to sleep with 2000 calories in the tank, by time you woke up the next morning, you were probably down to 1400-1600. If you ate the oatmeal at 5am, you were probably close to 2000 by time the gun fired, but then you only took in about 600 during the run. If you ate after 6am, then you probably had a store of about 1500 calories when the gun fired, and the oatmeal would count in the 950. See Tim Noakes, the Lore of Running. Noakes has a long discussion in his book about energy stores and how we use them. I forget the exact chapter. Among other things, he writes: "The marathon is less a physical event than a spiritual encounter. In infinite wisdom, God built into us a 32 km racing limit, a limit imposed by inadequate sources of the marathoner's prime racing fuel -- carbohydrates. But we, in our infinite wisdom, decreed that the standard marathon be raced over 42 km...So it is in that physical no-man's-land, which begins after the 32 km mark, that is the irresistible appeal of the marathon lies. It is at this stage, as the limits to human running endurance are approached, that the marathon ceases to be a physical event...It is there that you learn something about yourself and your view of life." (Noakes, Lore of Running, p596)


      Needs more cowbell!

        Trent, doesn't this sort of assume that most folks are eating "ample" carbs...like the RDA 300 grams/day? Most days I eat about a third that amount in net carbs. I would guess that for those of us who eat lower levels of carbs most of the week that carb-ups a day or two before our weekly long run are neccessary, right? k

        I shoot pretty things! ~

        '14 Goals:

        • 2 olympic distance duathlons -- 6 days apart -- PR at least 1

        • 130#s (and stay there, gotdammit!)


        A Dance with Monkeys

          That is reasonable. It is hard to run while consuming a low-carb diet. See my post on food for running.


          Needs more cowbell!

            That is reasonable. It is hard to run while consuming a low-carb diet. See my post on food for running.
            Yep, it's hard if I don't really pay close attention to my carb levels. When I tried to keep my carbs lower every day it killed my longer runs. I don't bonk at all if I really "schedule" my carbs along with my long runs. I don't know how the average non-runner really *needs* 300 carbs/day if I can happily run close to 30 miles/week without eating that much most days. If I ate that much every day I'd be a hypoglycemic mess and wanting Krispy Kremes every night before bed. k

            I shoot pretty things! ~

            '14 Goals:

            • 2 olympic distance duathlons -- 6 days apart -- PR at least 1

            • 130#s (and stay there, gotdammit!)

              I estimate I take in at least 300g/carbs a day, and those would be my non-running days. Most calories above 2000kcals daily tend to be carbs also. My challenge is remembering to take in enough protein, because I take in at least 30% daily cals in fat to ward off illness and injury. Protein tends to fall to the side a little. That being said, I don't love carbo loading for races, especially the time Trent made me stuff 3000kcals down two days in a row. What I have found works pretty well is training my body to run well on the nutrients I regularly provide. For example, a 600-800kcal breakfast of mostly carbs ensures a well nutrited evening run, and before most races half marathon or up,I'll take in 1000kcals of carbs at least 3 hrs before the race. For long runs, 20 milers, I take in some gatorade, but mostly water, so I can better see any holes in my daily nutrition. If I bonk on a run like a 20, I'm not getting enough carbs on a regular basis or I underate the night before.