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  1. #1
    Senior Member Dieter's Avatar
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    Been reading a lot the past couple of months. Much of that reading has been heavy on the chemistry, so I have tried to simplified things a little to organize my thoughts. Please correct me if that has led to mistakes...



    When energy is required to perform exercise the muscles get their supply from the breakdown of ATP. The body has a limited store of ATP and would use it up very quickly (in about 2 seconds) if we did not have ways of resynthesising it. There are three systems that produce energy to resynthesise ATP:
    ATP-PC, lactic acid and aerobic.

    The Anaerobic (ATP-CP) Energy System
    The resynthesis of ATP from Creatine/Phosphate (CP) will continue until CP stores are depleted, approximately 4 to 5 seconds. This gives us around 5 to 7 seconds of ATP production. To develop this energy system, sessions of 4 to 7 seconds of high intensity work at near peak velocity are required. The way I understand it this is more important for people running sprints etc, and not so much for us bicyclists.

    The Anaerobic Lactate (Glycolytic) System
    The lactic acid system is capable of releasing energy to resynthesise ATP without the involvement of oxygen. To understand this I have first taken a few steps back.

    Glycolysis (breakdown of carbohydrates) results in the formation of pyruvic acid and hydrogens ions (H+). The accumulation of hydrogen ions is the limiting factor causing fatigue. A build up of H+ will make the muscle cells acidic and interfere with their operation. Up to a certain point a carrier molecule called NAD+ will remove this H+ by combining the two and form NADH. The NADH makes its way through the body, and eventually releases the H+ so it can be combined with oxygen to form H2O. This is aerobic breakdown of pyruvic acid.

    If there is insufficient oxygen then NADH cannot release the H+ and they build up in the cell. The resulting acidic environment will slow down enzyme activity and ultimately the breakdown of glucose itself. To prevent this rise in acidity the NADH will instead fuel another reaction: reducing pyruvic acid to lactic acid. This reaction also results in the regeneration of NAD+, which in turn allows removal of more H+.

    At high intensities of training a large percentage of the pyruvic acid produced is converted to lactic acid. Although about 80% of the lactic acid diffuses from the skeletal muscles and is transported to the liver (where it is converted back to glucose or glycogen), some lactic acid accumulates in muscle. Ultimately, once adequate oxygen is available, lactic acid must be catabolized completely into carbon dioxide and water. After exercise has stopped, extra oxygen is required to metabolize lactic acid; to replenish ATP, PC, and glycogen; and to pay back any oxygen that has been borrowed from hemoglobin, myoglobin (an iron-containing substance similar to hemoglobin that is found in muscle fibers), air in the lungs, and body fluids. The additional oxygen that must be taken into the body after vigorous exercise to restore all systems to their normal states is called oxygen debt (A.V. Hill 1886-1977). The debt is paid back by labored breathing that continues after exercise has stopped.

    Eventually, muscle glycogen must also be restored. This is accomplished through diet and may take several days, depending on the intensity of exercise. The maximum rate of oxygen consumption during the aerobic catabolism of pyruvic acid is called "maximal oxygen uptake". It is determined by sex (higher in males), age (highest at about age 20) and size (increases with body size). Highly trained athletes can have maximal oxygen uptakes that are twice that of average people, probably owing to a combination of genetics and training. As a result, they are capable of greater muscular activity without increasing their lactic acid production, and their oxygen debts are less. It is for these reasons that they do not become short of breath as readily as untrained individuals.

    The normal pH of the muscle cell is 7.1 but if the build up of H+ continues and pH is reduced to around 6.5 then muscle contraction may be impaired and the low pH will stimulate the free nerve endings in the muscle resulting in the perception of pain (the burn). This point is often measured as the lactic threshold or anaerobic threshold or onset of blood lactate accumulation (OBLA).

    Lactic acid (lactate) is in other words not:
    - responsible for the burn in the leg muscles when exercising very fast
    - responsible for the soreness you experience in the 48 hours following a hard session
    - a waste product.

    Lactate, which is produced by the body all day long, is resynthesized by the liver to form glucose which in turn provides more energy!


    The Aerobic Energy System
    The aerobic energy system utilises proteins, fats and carbohydrate (glycogen) for resynthesising ATP. It can typically be improved by doing long sessions at 50 to 70% of maximum heart rate. This places demands on muscle and liver glycogen.

    The normal response by the system is to enhance muscle and liver glycogen storage capacities. These long steady sessions will also develop the aerobic capacity by means of capillarisation (formation of more small blood vessels, thus enhancing oxygen transport to the muscles) and by creating greater efficiency in the heart and lungs. If the aerobic capacity is greater, it means there will be more oxygen available to the working muscles and this should delay the onset of lactic acid at a given work intensity.
    Last edited by Dieter; 10-05-05 at 06:12 PM.

  2. #2
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    pretty much yes except yes you will use the atp path way at the start of heavy sprints.

    But your understanding of lacate is wrong like most others, if you train right you can re-use lacate as energy, plus you can build muscle ph tolerance to. have a read off this.

    http://www.cyclingnews.com/fitness.p...ctic_frederick

    oh and most of the soreness is the damage muscle fibres in the muscle.

  3. #3
    Senior Member Dieter's Avatar
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    Quote Originally Posted by russdaz
    pretty much yes except yes you will use the atp path way at the start of heavy sprints.

    But your understanding of lacate is wrong like most others, if you train right you can re-use lacate as energy, plus you can build muscle ph tolerance to. have a read off this.

    http://www.cyclingnews.com/fitness.p...ctic_frederick

    oh and most of the soreness is the damage muscle fibres in the muscle.
    What I wrote was that

    Lactic acid (lactate) is in other words not:
    - responsible for the burn in the leg muscles when exercising very fast
    - responsible for the soreness you experience in the 48 hours following a hard session
    - a waste product.

    Lactate, which is produced by the body all day long, is resynthesized by the liver to form glucose which in turn provides more energy!


    Do you agree with it then? Thanks for the link by the way! Good article and some interesting references. Will try to digg up a few of those.

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    Senior Member DannoXYZ's Avatar
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    lactic acid and lactate are not the same thing...

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    Senior Member Dieter's Avatar
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    Quote Originally Posted by DannoXYZ
    lactic acid and lactate are not the same thing...
    Good point. The article provided by Russdaz actually explains just that very well.

    Would I be right if I say that:

    - Pyruvic Acid into Lactic Acid binds two H+ ions. One freee and one "taken" from NADH, making this NAD+
    - Lactic acid then breaks down further to produce lactate and H+.

    In total that process "gets rid of" one H+, and provides some ATP. In addition you get lactate, which can be converted to energy in itself.

    What is then the limiting factor in the system?

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    Sorry i miss read part of your post, must have skiped over the not resposible part

    but

    your limiting factor is your bodies ability to buffer h+ and your vo2 max

    training at near max heart rate increases you'r bicarbonate buffering system, thats the mechinism to fight H+ in the muscle, the higher your buffer system the more H+ you can work with before onset of fatigue.

    The H+ combines with the bicarbonate to cause the waste product hco3, as you reach the end of you buffering capabilities you fatigue. once you start gettin o2 back into the muscles the hco3 breaks down to co2 and h2o.

    The higher your vo2 max the quicker you get rid of resultant co2 dept from the working muscles.

    At least thats the threory iv been told.

    by doing lots of TT type events i can hold 95% average max heart rate for upto 90min's, and have a max of 210. my vo2 score is predicted at 65-75 based on a tradmil test and Polar testing. i need to have this figue comfimed soon i hope.

    hope thats right is 3am here and im now tired. lol

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    Senior Member DannoXYZ's Avatar
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    "What is then the limiting factor in the system?"

    How quickly your body can deliver O2 to the mitochondria. This requires a heart that can pump a lot of volume. Training and conditioning will actually increase the volume per pump to +25-33% over initial sedentary state.

    Another variable is an expansive capillary network moving this blood to each muscle fibre improves O2 delivery. These capillaries are built during the base-training/endurance phase. The body responds to extended-time efforts requiring a lot of energy and 3-4 hour rides taxes your energy system. It's best to ride slow enough to work up to this distance/time to build up the energy-delivery system first, then work on speed & strength next once you've developed the underlying infrastructure.

    Muscle-strength is the next variable in selecting PC, glycogen or fats for ATP production. If you require muscles to exert 95-100% of their max-effort, they will most likely be using PC and muscle-glycogen. Muscle-exertions at the LT is typically around 60-70% max-force exertion level. At exertion-levels below 55-60%, the lactic acid build-up is slow enough that it can be cleared out about as fast as it builds.

    Obviously, building up stronger muscles will have them operate further away from their max-effort for any given power-output. One of the most efficient athletes I saw at the OTC was a football-player linebacker. For the amount of power he generates on the erg, the consumed the lowest amounts of O2 ever recorded. But he was a little too heavy and bulky for a bike-racer, so you strike a balance of muscle-strength and size somewhere. In general, cyclists can use some more strength-training.
    Last edited by DannoXYZ; 10-05-05 at 11:48 PM.

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    Senior Member Dieter's Avatar
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    Quote Originally Posted by russdaz
    Sorry i miss read part of your post, must have skiped over the not resposible part

    but

    your limiting factor is your bodies ability to buffer h+ and your vo2 max

    training at near max heart rate increases you'r bicarbonate buffering system, thats the mechinism to fight H+ in the muscle, the higher your buffer system the more H+ you can work with before onset of fatigue.

    The H+ combines with the bicarbonate to cause the waste product hco3, as you reach the end of you buffering capabilities you fatigue. once you start gettin o2 back into the muscles the hco3 breaks down to co2 and h2o.

    The higher your vo2 max the quicker you get rid of resultant co2 dept from the working muscles.

    At least thats the threory iv been told.

    by doing lots of TT type events i can hold 95% average max heart rate for upto 90min's, and have a max of 210. my vo2 score is predicted at 65-75 based on a tradmil test and Polar testing. i need to have this figue comfimed soon i hope.

    hope thats right is 3am here and im now tired. lol
    I whish I had those TT stats!

    Is it possible to increase the bicarbonate buffer somehow? I mean... Can that be done through eating specific ways, or can the system be stimulated through excersise for instance?

  9. #9
    Senior Member Dieter's Avatar
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    Quote Originally Posted by DannoXYZ
    "What is then the limiting factor in the system?"

    How quickly your body can deliver O2 to the mitochondria. This requires a heart that can pump a lot of volume. Training and conditioning will actually increase the volume per pump to +25-33% over initial sedentary state.

    Another variable is an expansive capillary network move this blood to each muscle fibre improves O2 delivery. These capillaries are built during the base-training/endurance phase. The body responds to extended-time efforts requiring a lot of energy and 3-4 hour rides taxes your energy system. It's best to ride slow enough to work up to this distance and time of rides to build up the energy system first, then work on speed & strength next once you've developed the underlying infrastructure.
    OK... So the mithocondria is where the H+ of the NADH combines with oxygen, forming NAD+ and H2O. I would then interpret the ability of the mithocondria to make this transformation the limiting factor for how intense you can perform while still staying aerobic: as you get more fit you increase the ability of the body to deliver more O2 ,along with developing more capilaries. This allows you to perform the same amount of work at a lower HR than before. Another way of saying it would be that you can put out more watts before hitting your lactate threshold than before - the body is more efficient at flushing away the H+

    But what is the limiting factor for anaerobic activity? According to my previous equation H+ is taken care of by the transformation of pyruvic acid -> lactic acid -> lactate. This cannot be completey right, not indefinitely anyways. So something has to accumulate somewhere, or there is a limiting factor in the bodys ability to perform one of those transformations. Where did I oversimplify?


    Quote Originally Posted by DannoXYZ
    Obviously, building up stronger muscles will have them operate further away from their max-effort for any given power-output. One of the most efficient athletes I saw at the OTC was a football-player linebacker. For the amount of power he generates on the erg, the consumed the lowest amounts of O2. But he was a little too heavy and bulky for a bike-racer, so you strike a balance of muscle-strength and size somewhere. In general, cyclists can use some more strength-training.
    I found some more interesting articles on the page Russdaz provided (thanks again!). One was arguing that there was no link between weight training and cycling efficiency:

    http://www.cyclingnews.com/fitness/?id=strengthstern

  10. #10
    Senior Member DannoXYZ's Avatar
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    Quote Originally Posted by Dieter
    Is it possible to increase the bicarbonate buffer somehow? I mean... Can that be done through eating specific ways, or can the system be stimulated through excersise for instance?
    Yes, I take 2-tablespoons of bicarbonate in 1/2 liter of water 20-minutes before a track event. This really only helps in 100% maximum-effort events like sprinting where lactic-acid build-up causes a problem in the muscle cells. I haven't noticed it to be much of an aid in time-trials, and there's absolutely zero endurance benefits. The effect seems to be best from 20-40 minutes after taking it. Stomach upsets and puking are also a side-effect one should be aware of...


    Quote Originally Posted by Dieter
    But what is the limiting factor for anaerobic activity? According to my previous equation H+ is taken care of by the transformation of pyruvic acid -> lactic acid -> lactate. This cannot be completey right, not indefinitely anyways. So something has to accumulate somewhere, or there is a limiting factor in the bodys ability to perform one of those transformations. Where did I oversimplify?
    The main limitation in anaerobic fermentation is the enzyme phosphofructokinase.


    Quote Originally Posted by Dieter
    I found some more interesting articles on the page Russdaz provided (thanks again!). One was arguing that there was no link between weight training and cycling efficiency:

    http://www.cyclingnews.com/fitness/?id=strengthstern
    It really depends upon where you are in your training-level and how close you are to your genetic potential. I would not deign to suggest to Lance that he needs to practice spinning in circles to improve his effeciency... heh, heh.. a guy who averages 110rpm. But to any new rider with less than 5 years experience, yes, working on smooth circular pedals strokes would yield major improvements in their performance.

    Same thing with weight-training and building strength. Beginners who end up with sore legs and muscles that doesn't recover fully by the next day can certainly use strength-training. Up until the point where they can recover fully in 1-day, strength-training will be of benefit. Once you get up to RAAM levels of performance (20-hours/day) or TDF where you can do 4-6 hour rides and do it again and again day after day, then strength-training won't make much of a difference. The key objective at this point is to further develop the aerobic system and raise VO2-max; being able to process more O2 per second.
    Last edited by DannoXYZ; 10-05-05 at 11:40 PM.

  11. #11
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    bicarb is for events less than 7 mins.

    What is the limiting factor? Stroke volume x max heart rate.

    Good to see some hard biochem instead of ocp crap. I always think your posts are right on the money dannyxyz

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    Quote Originally Posted by Dieter
    OK... So the mithocondria is where the H+ of the NADH combines with oxygen, forming NAD+ and H2O. I would then interpret the ability of the mithocondria to make this transformation the limiting factor for how intense you can perform while still staying aerobic: as you get more fit you increase the ability of the body to deliver more O2 ,along with developing more capilaries. This allows you to perform the same amount of work at a lower HR than before. Another way of saying it would be that you can put out more watts before hitting your lactate threshold than before - the body is more efficient at flushing away the H+

    But what is the limiting factor for anaerobic activity? According to my previous equation H+ is taken care of by the transformation of pyruvic acid -> lactic acid -> lactate. This cannot be completey right, not indefinitely anyways. So something has to accumulate somewhere, or there is a limiting factor in the bodys ability to perform one of those transformations. Where did I oversimplify?




    I found some more interesting articles on the page Russdaz provided (thanks again!). One was arguing that there was no link between weight training and cycling efficiency:

    http://www.cyclingnews.com/fitness/?id=strengthstern
    Not really. The limiting factor is not the inability of mitochondria to undergo the ETC and Krebs, it's always the lack of oxygen. With a limited amount of oxygen, there is more lactate accumulation, since Krebs happens less frequently because of the lack of oxygen. If you interpret the name "anaerobic", it means "without oxygen". When anaerobic, pyruvic acid is reduced to lactic acid and glycolysis follows a specific pathway. Eventually, the oxidation of 1 molecule of glucose to pyruvic acid results in a net gain of only 2 ATP and 2 NADH.


    Does that help?

    Koffee

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    Killing Rabbits
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    Quote Originally Posted by koffee brown
    With a limited amount of oxygen, there is more lactate accumulation, since Krebs happens less frequently because of the lack of oxygen.
    Koffee
    And why is there limited oxygen? It is not respiratory limitations, it is cardiac output. Capillary density can be increased via training so it's not at the cell interface.

  14. #14
    Senior Member DannoXYZ's Avatar
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    Imagine there's a garden hose going into each cell that delivers oxygen. This feeds aerobic glycolysis. Let's say you have this garden hose turned up all the way to deliver as much O2 as possible into the cell; you're going at a TT pace. Assuming say... ALL of the leg muscles are operating at the same level, you have the following energy outputs:

    aerobic glycolysis = 15 calories/min or 900 calories/hour

    However, you get passed by the knave coming up to a hill, so you gotta turn up the speed, but you cannot introduce O2 into your muscle cells any faster, you exert the muscles even more and resort to:

    anaerobic glycolysis = 35 calories/min or 2100 calories/hour

    However, this process is only 1/20th as efficient as aerobic glycolysis and you burn through the glycogen much faster. But the knave's still getting away... so you crank on the pedals even harder, to 100% maximum-effort and use the PC:

    phosphocreatine = 70 calories/min or 4200 calories/hour

    Now you're really cranking up the power, but it'll only last for about 10-seconds; just enough to make it to the top of the hill...

    The variables you want to examine is the various rates of ATP production per second (mmoles/sec). Match this up to the rate of O2 input into the cells and you can figure out what the maximum ATP/sec. rate aerobic glycolysis supports. Above this rate, higher ATP/sec needs will switch to anaerobic and PC pathways.

    BTW - didn't really answer your question above. You didn't really mean "rate" of anaerobic activity like I assumed. You really mean what "stops" an anaerobic effort like a sprint right? Why can't you do a sprint indefinitely? Well, anaerobic fermentation builds up H+ faster than can be cleared out and NAD runs out.
    Last edited by DannoXYZ; 10-07-05 at 12:15 PM.

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    You dont need to train low down in your heart tate to Increase capillarisation. it also happens in zone 5 to.

    Can you increase you muscle buffering? yep zone 6

    Zone 5
    TT
    MTB XC
    Road racing
    Track endurance
    TT
    Suitable for indoor workouts
    Increased VO2 max
    Increased lactate threshold
    Race specific skills
    Increased oxidative / glycolytic enzymes
    Increased capillarisation

    Zone 6 Maximal
    MTB XC
    Road racing
    Track endurance
    TT
    Suitable for indoor workouts
    Increased VO2 max
    Increased lactate threshold
    Increased blood volume
    Increased stroke volume
    Increased muscle buffering capability
    Increased lactate clearance
    Increased glycolytic enzymes

    Zone 7 Maximal Supramaximal
    Road racing
    Track endurance
    Suitable for indoor workouts
    Increased VO2 max
    Fast twitch muscle fibre development
    Increased neurological recruitment
    Increased peak power output

    http://www.cyclingnews.com/fitness/?id=powerstern

    an example would be something like this, the last 15min are my cool. and the warm up has already happened.
    Last edited by russdaz; 10-06-05 at 05:17 AM.

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    Just ride. roadbuzz's Avatar
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    Quote Originally Posted by Enthalpic
    And why is there limited oxygen? It is not respiratory limitations, it is cardiac output. Capillary density can be increased via training so it's not at the cell interface.
    Huh? Aren't all components of the oxygen delivery system critical? Lung capacity, red blood cell count, blood volume, as well as heart stroke volume and capillarization are factors.

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    Quote Originally Posted by roadbuzz
    Huh? Aren't all components of the oxygen delivery system critical? Lung capacity, red blood cell count, blood volume, as well as heart stroke volume and capillarization are factors.
    Maybe im mis understanding the question.

    i think he's after the limiting factor of anerobic function.

    the better you lung capacity red blood cells volume etc etc, increases your aerobic zone. it also increases your recovery from oxygen debt too.
    but its not your limiting factor against anerobic levels

  18. #18
    Senior Member DannoXYZ's Avatar
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    Quote Originally Posted by roadbuzz
    Huh? Aren't all components of the oxygen delivery system critical? Lung capacity, red blood cell count, blood volume, as well as heart stroke volume and capillarization are factors.
    Yeah, there's a time-delay with aerobic capacity in relation to anaerobic workout. But that's primarily in recovery after the effort has ended (excess ATP is requried to synthesize PC). But in-the-monent, once you're exerting power beyond what aerobic glycolysis can provide, O2 is no longer a limitation, it's all anaerobic above that.

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    Senior Member Dieter's Avatar
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    Quote Originally Posted by DannoXYZ
    BTW - didn't really answer your question above. You didn't really mean "rate" of anaerobic activity like I assumed. You really mean what "stops" an anaerobic effort like a sprint right? Why can't you do a sprint indefinitely? Well, anaerobic fermentation builds up H+ faster than can be cleared out and NAD runs out.
    Yes, this was what I was after. There had to be some bottleneck somewhere not allowing all H+ to be removed from the muscles, otherwise you wouldn't be getting the burning sesation.

    Thanks a lot everyone for helping me with this, I think I am starting to get a certain understanding of it now.


    On a slightly related subject... A friend of mine keeps telling me its a proven fact that working out in the morning is more efficient than the same type of workout later in the day if your main goal is to loose weight. Your muscles are forced to use fat for energy because of low glycogen stores in the morning she sais. Unfortunately she is unable to provide articles on those proven facts, so I promised I would look into it.

    To me this sounds a bit weird, as I would think the body did not have a greater ability to convert fat into ATP in the morning than it would later in the day. I can see the possibility of bonking being higher though... I did a search on this, but most of those topics took a different turn (thanks Koffee for some interesting posts about GI hype and carbs in the morning). Anyone have any articles or just facts that can support my friend being right or wrong?

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    Senior Member Richard Cranium's Avatar
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    In many Pro-cyclists these ARE the limiting factors -- " Lung capacity, red blood cell count, blood volume".

    Just bear in mind you have to have the will-power and muscle tissue availible to "outrun" oxygen transport limitations. In practice, the are many energy substrates that aren't used in a "perfectly coordinated manner", leading to inefficiencies in muscle fibers with respect to cellular metabolism. In other words, limiting factors vary with selected exercise load, rest, training and current enviromental circumstance. (altitude, temp, etc)

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    Killing Rabbits
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    Quote Originally Posted by Dieter
    A friend of mine keeps telling me its a proven fact that working out in the morning is more efficient than the same type of workout later in the day if your main goal is to loose weight.
    The theory is that your glycogen levels are low in the morning due to your overnight fast and that your body will only have fat to use as fuel. I did have a good article on that but I can't find it now. The "glycogen sparing" effect was found to be very small to none. Caffeine has been reported to have glycogen sparing effects as well with some moderate results.

    However, post exercise immunosuppression is real and this can be limited by proper nutrition; before, during and after exercise. Even if you are trying to lose weight, consuming 200kcal/hour is more than compensated for by the 600+ you will be burning and will help you ride further and healthier.

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