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  1. #1
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    Bonking Vs Hitting the Wall: differences?

    I was reading an old thread on Lactate and stumbled upon this intersting point from user Cyclopod:
    Quote. During long excersize efforts, muscle glycogen depleation is what causes bonking (different from hitting the wall, when glycogen in the liver is depleated). Unquote

    Can anybody confirm that this statement is correct?
    It happened once on an early season training ride that I couldnt even get home and asked to be picked up by the wife.
    Was it an extreme bonking, or did I hit the wall?

    I thought that the two terms were equivalent??
    thanks
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  2. #2
    AZ
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    I have always viewed the two terms differently , but have always seen them used interchangabley . No science to back up my views , I view hitting the wall as a function of limits of endurance . Bonking on the other hand , I view as limits of hydration , nutrition , or both .

  3. #3
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    I believe in the "central governer" theory.. the brain decides when its time to stop. And the brain makes this decision largely based on blood glucose levels.. consume carbs during the ride.

    Muscle glycogen is a necessary fuel for high intensity, but low blood sugar (glucose) may end my ride before I reach a state of depleted muscle glycogen.

    Maintain a good blood glucose and I will burn less muscle glycogen and perform at a higher level (as opposed to not fueling during the ride) even after I have depleted my muscle glycogen.

    For 90min or longer I like around 200cal per hour.. like a powerbar per hour or so. For racing I will shoot for 300cal per hour. I like powerbars, yummy.. cookies and cream, caramel, and chocolate PB are my faves.. but any sugar bar will do. Fig Newtons rock! Drink mixes work killer, so do gels for racing, but during training and riding I like to eat.

  4. #4
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    For me bonking is when I run out of glycogen stores, then I can only go has fast has the liver can make glycogen....that is about 20 kph on a flat road.

    Hitting the wall not sure what that is????

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    Historically, I believe that bonking is to cycling as hitting the wall is to running. Same thing, just different terminology between sports.

  6. #6
    BBW
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    Quote Originally Posted by CT Mike
    Historically, I believe that bonking is to cycling as hitting the wall is to running. Same thing, just different terminology between sports.
    Same thing. They refer to a low blood glucose. When muscle glycogen is low then blood glucose is used to power the muscles and the rest of the tissues (which cannot be sustained for long); a drop in blood glucose will let you know that you need to decrease dramatically the intensity of the exercise or stop completely (so you relly less on glucose). Depending on the intensity of that hypoglycemia you could experiment dizziness, chills, profuse sweating, weakness, etc or not.

  7. #7
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    Quote Originally Posted by BBW
    Depending on the intensity of that hypoglycemia you could experiment dizziness, chills, profuse sweating, weakness, etc or not.
    Sounds like the last 25 minutes of every race. Fun times!
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  8. #8
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    Isn't it a cyclist vs. runner semantic for what is effectively "exhaustion" - "bonking" for the former, and "hitting the wall" for the latter?

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    I always thought bonking was a sugar low, solvable by eating some food and taking it easy for 20 minutes or so, while hitting the wall was truly hitting your limits, your legs just won't go no more.

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    Thanks for the interesting feedback.
    Most of the replies confirm my initial suspect: the two terms are interchangeable and really mean the same thing (exhaustion-hypoglycemia).

    I think that the severity of the bonking/exhaustion depends on the glycogen depletion on different storage systems. Like, the muscle glycogen is depleted first, then the blood glycogen will go next and the liver glycogen is the last resource to be burned?

    Can anybody with more scientific background confirm this?
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    Quote Originally Posted by Ausable
    I think that the severity of the bonking/exhaustion depends on the glycogen depletion on different storage systems. Like, the muscle glycogen is depleted first, then the blood glycogen will go next and the liver glycogen is the last resource to be burned?
    That's the general trend. Its a fluid process, you don't necessarily see complete depletion occur in each area because there the goal is to replenish stores and support muscle glucose uptake. When liver glucose output drops below muscle glucose uptake that when you really start to have issues.

    The processes are obviously a bit more complex than this and will depend heavily on activity intensity and duration.

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    Per: http://www.moniqueryan.com/books/books.html

    I just happen to be reading it (again), a very good book for the basics of sports nutrition (mainstream thinking). I have also studied several other resources, mostly based on the coyle/coggan studies.

    Glucose is stored in the muscles and liver (as glycogen). The muscles, fully loaded have about 2000 calories worth, The liver about 400. And as circulating glucose (blood) about 80 calories.

    Thats the onboard fully loaded glucose supply. The brain needs glucose, so maintaining blood glucose is important for sharp thinking. As blood glucose declines, the liver will release stored glycogen to support the blood glucose level.. but frankly, 400cals is not much and I can feel it fading shortly after an hour (or less if I wasn't fully loaded) of hard riding.

    Muscle glycogen is direct fuel for the muscles. When liver glycogen depletes, blood glucose will not be raised by what is stored in the muscles.. I may fade even with muscle glycogen still available.

    The rate of muscle glycogen depletion is based on intensity and the level of muscle glycogen. As muscle glycogen depletes, the body will shift to a higher % of fat as fuel. This is important to realize.. as long as I maintain blood glucose levels, I can continue to ride at solid intensities even as muscle glycogen becomes somewhat depleted. I may not be able to ride at max, but as long as blood glucose is maintained, I can ride at surprising power levels with low muscle glycogen.

    Long hard rides, consecutive days of hard training, or training in a depleted state may train the body to better perform when muscle glycogen is low. The key is to always maintain blood glucose levels, by ingesting carbohydrates during excersize.

    Lastly, time to exhaustion, and performance varies based on the levels of glucose storage prior to excersize.. so if I want to perform best, I must be properly fueled for the training or event.

  13. #13
    BBW
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    Quote Originally Posted by Ausable
    Thanks for the interesting feedback.
    Most of the replies confirm my initial suspect: the two terms are interchangeable and really mean the same thing (exhaustion-hypoglycemia).

    I think that the severity of the bonking/exhaustion depends on the glycogen depletion on different storage systems. Like, the muscle glycogen is depleted first, then the blood glycogen will go next and the liver glycogen is the last resource to be burned?

    Can anybody with more scientific background confirm this?
    Many answers here are correct; let me be more specific and clear your doubt.

    as stated, muscle glycogen is for the use of the muscle (glycogen stored in your quads is for your quads only and cannot go any other place to supply carbs. This is because the muscle lacks the enzyme 'glucose phosphatase" that enables the glucose to get out of the cell)
    On the other hand, the liver is a "central" reservoir that is in charge of maintaining blood glucose levels and one of the reasons is because the central nervous system (brain, neurons) among other tissues (red blood cells for example) use exclusively glucose as a fuel source in "normal conditions" (not talking about diabetics or other"abnormal" situations). The liver, as you guessed has that enzyme that enables the glucose to get out of the liver.

    If you are performing biceps curls (many of them for a looong time), you might deplete your biceps glycogen stores but less likely you will deplete your liver stores.

    During cycling (since the legs are bigger muscles), if the intensity is high enough and you exercise during a prolonged time (>90 min), the glycogen stores will decrease and you will rely more on blood glucose to fuel that high intensity exercise.

    Then you have 3 options:

    1- Decrease intensity so you rely less on carbs and rely more on fats
    2- Keep exercising at high intensity until you start getting symptoms of hypoglycemia
    3- Not let the glycogen level to drop, eating carbs during exercise if this is going to be high intensity and more than 1 hour in duration.

    Now, as your leg glycogen store gets depleted and your liver glycogen starts to become a greater source of fuel the problem is that the liver glucose output cannot sustain the demands of both, legs and central nervous system, so blood glucose starts dropping.
    Depending on how severe the drop is, you will feel more or less symptoms of a hypoglycemia and you will bonk. Meanwhile, your liver through a process called gluconeogenesis, will attemp to maintain blood glucose levels through the synthesis of glucose from amino acids coming from the muscle (muscle breakdown or proteolysis; and this is one of the reasons why you don't want to get out of carbs ) and glycerol coming from the fats. It will not be enough to support high intensity exercise but just enough to not cause brain damage (your brain is more sensitive to a lack in glucose than a lack of oxygen. have you heard of people drowning in cold water and being without oxygen for 10 minutes and survive? 10 minutes without glucose and you are dead my friend )

    Hope this helps

  14. #14
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    Quote Originally Posted by perryr
    Long hard rides, consecutive days of hard training, or training in a depleted state may train the body to better perform when muscle glycogen is low.
    I would also say those things trigger your muscle cells to adapt to the stress by increasing cellular muscle glycogen storage capacity. That's the lesson of this thread, to me.
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  15. #15
    LMN
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    Bonking; a truely horrible experience. You know you have bonked if
    a) you would trade your bike for food.
    b) you think you are going to die.
    c) you are unable to carry on a conversation.
    d) you are staring at your BB and weaving all over the road.

    Hitting the Wall:
    a) Energy is good but your legs have no power.
    b) You heart rate is up but you aren't going any fast.
    c) You can still talk and have fun but you are not going anywhere quickly.


    Some where in this thread was posted about "bonk training" (riding until you bonk in order to increase your ability to store gylocgen). IMHO the advantages of this are greatly out weighed by the disadvantages. When you bonk the recovery time is huge. A true bonk takes so long to recover from that you lose fitness in that time.

  16. #16
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    Quote Originally Posted by LMN
    Some where in this thread was posted about "bonk training" (riding until you bonk in order to increase your ability to store gylocgen). IMHO the advantages of this are greatly out weighed by the disadvantages. When you bonk the recovery time is huge. A true bonk takes so long to recover from that you lose fitness in that time.
    Probably not as relevant to XC racing where the races are only around 2 hours, but it definitely helps on the road where the crucial selection is usually made close to the end, after everybody already has 3-4 hours in their legs.

    http://blog.trainingpeaks.com/2009/0...ter-allen.html

    "You definitely can make it to two hours. Maybe you need to build up to it first, by going an hour, hour and half and then two hours. It sounds like you both(as most cyclists have) have really trained your bodies to burn carbs first and ignore the fat stores no matter what level of intensity. I used to do a ton of rock climbing and mountaineering(after retiring from pro cycling) and it was amazing that all of these mountaineers had trained their bodies the exact opposite of bike racers. They could go at a solid endurance/tempo pace for not only hours, but days(!) without much food. I was bonking every 3 hours if I wasn’t constantly eating and I had more body fat then they did! I don’t know of any scientific studies, so this one has to be categorized in the ‘folk lore’ category for now. However, I know it works and I have seen people change this with some concerted effort.
    Hunter"

  17. #17
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    Quote Originally Posted by BBW
    Many answers here are correct; let me be more specific and clear your doubt.

    as stated, muscle glycogen is for the use of the muscle (glycogen stored in your quads is for your quads only and cannot go any other place to supply carbs. This is because the muscle lacks the enzyme 'glucose phosphatase" that enables the glucose to get out of the cell)
    On the other hand, the liver is a "central" reservoir that is in charge of maintaining blood glucose levels and one of the reasons is because the central nervous system (brain, neurons) among other tissues (red blood cells for example) use exclusively glucose as a fuel source in "normal conditions" (not talking about diabetics or other"abnormal" situations). The liver, as you guessed has that enzyme that enables the glucose to get out of the liver.

    If you are performing biceps curls (many of them for a looong time), you might deplete your biceps glycogen stores but less likely you will deplete your liver stores.

    During cycling (since the legs are bigger muscles), if the intensity is high enough and you exercise during a prolonged time (>90 min), the glycogen stores will decrease and you will rely more on blood glucose to fuel that high intensity exercise.

    Then you have 3 options:

    1- Decrease intensity so you rely less on carbs and rely more on fats
    2- Keep exercising at high intensity until you start getting symptoms of hypoglycemia
    3- Not let the glycogen level to drop, eating carbs during exercise if this is going to be high intensity and more than 1 hour in duration.

    Now, as your leg glycogen store gets depleted and your liver glycogen starts to become a greater source of fuel the problem is that the liver glucose output cannot sustain the demands of both, legs and central nervous system, so blood glucose starts dropping.
    Depending on how severe the drop is, you will feel more or less symptoms of a hypoglycemia and you will bonk. Meanwhile, your liver through a process called gluconeogenesis, will attemp to maintain blood glucose levels through the synthesis of glucose from amino acids coming from the muscle (muscle breakdown or proteolysis; and this is one of the reasons why you don't want to get out of carbs ) and glycerol coming from the fats. It will not be enough to support high intensity exercise but just enough to not cause brain damage (your brain is more sensitive to a lack in glucose than a lack of oxygen. have you heard of people drowning in cold water and being without oxygen for 10 minutes and survive? 10 minutes without glucose and you are dead my friend )

    Hope this helps
    Hi BBW, I can appreciate the advice because I have been dealing with hypoglycemia due to my inability to digest simple carbohydrates and sugars for years and I have pushed myself too hard many times and did not realize that I could potentially cause brain damage. Recently I started eating steamed vegetables with eight ounces of protein three meals a day also eating nuts and seeds for snacks and drinking spring water has been helping with the hypoglycemia. you could call it the paleolithic diet and its the only thing that seemed to help.
    cheers
    Johnny
    Local Bicycle Trader

  18. #18
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    LMN has it right. The quote you provided was backwards.

    Bonk = precipitous drop in blood sugar
    Wall = Leg muscles are out of glycogen

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