11-23-2006, 05:25 PM
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Latic Acid & Running
Most runners still believe that lactic acid is released during hard or unaccustomed exercise and that this is what limits running performance, as well as being the cause of stiffness. Neither is correct. But not even is the terminology of “lactic acid”.
Lactic acid does not exist as an acid in the body: it exists in another form called “lactate”, and it is this that is actually measured in the blood when “lactic acid” concentration is determined, as is done from time to time. This distinction is important not only for the sake of correctness, but more importantly, because lactate and lactic acid would have different physiological effects. The greatest myth is that lactic acid is the cause of the stiffness felt after an event such as a marathon. Stiffness is due mostly to damage to the muscle, and not an accumulation of lactic acid or lactic acid crystals in the muscle. Another misconception is that lactate is responsible for acidifying the blood, thereby causing fatigue. To the contrary, lactate is actually an important fuel that is used by the muscles during prolonged exercise. Lactate released from the muscle is converted in the liver to glucose, which is then used as an energy source. So rather than cause fatigue, it actually helps to delay a possible lowering of blood glucose concentration, a condition called hypoglycemia, and which will cause a runner to feel weak and fatigued if it occurs. A more recent addition to the muddled thinking is that of the anaerobic threshold. Pictures are seen of athletes having a blood sample taken with an accompanying caption indicating that the workout is being monitored by measuring “lactic acid”. The supposed rationale is that as running speed is increased, a point is reached at which there is insufficient oxygen available to the muscle and energy sources that do not require oxygen contribute to the energy that is needed. This results in a disproportionate increase in the blood lactate concentration, a point identified as the anaerobic threshold. This is also known as the lactate threshold or lactate 'turnpoint'. There are two problems with this. Firstly, the muscle never becomes anaerobic: there are other reasons for the supposed disproportionate increase that is measured in blood lactate concentration. Secondly, the so-called disproportionate increase causing a 'turnpoint' is not correct, in that the increase is actually smooth and incremental. This led to another way of using blood lactate concentration to monitor running performance. If blood lactate concentration is measured at different, increasing running speeds, it is possible to eventually draw a curve depicting the continued increase in concentration as the running speed gets faster. The position of this curve changes as fitness level changes. Particularly, the fitter a runner gets, the more the curve shifts to the right, meaning that at any given lactate concentration the running speed is higher than before. Often, the running speed at a lactate concentration of 4 mmol/l is used as a standard for comparison. This can also be used as a guide for training speed i.e. a runner could do some runs each week at the speed corresponding to the 4 mmol/l lactate concentration, some runs above this speed, and recovery runs at a slower speed. Of course, as fitness changes and the curve shifts, these speeds will change, and so a new curve will have to be determined. This is all very well, but the problem is to know how much running should be done below, at, and above the 4 mmol/l concentration. Remember, 4 mmol/l is a fairly arbitrarily chosen amount. Thus the real value in determining a “lactate curve” is to monitor how it shifts with training. The desirable shift is one in which a faster running speed is achieved at a given lactate concentration than before. This regular testing can be done in the laboratory with the athlete running on a treadmill or on a track in which running speed can be carefully controlled, such as by means of pace lights. Both types of testing are done at the Sports Science Institute, usually for research purposes. While useful information can be gained from regular testing to determine a runners’ lactate curve, it is important to keep in mind what is fact and what is fiction.         
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11-27-2006, 01:02 AM
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hmmm
okay wellllll actuallyy
i dont know if you're completely right, and i might be wrong but ... lactic acid is a byproduct of lactic acid fermentation. its produced when the muscle cells lack oxygen , which is usually after extreme workouts or what not our body needs to go through this because we need NAD+ stuff for glycolysis during anaerobic (no oxygen) respiration. so like our body doesn't really produce it on purpose, its just a side effect. and the more lactic acid that builds up..that's where the sore-ness comes from ..the acid build up.
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11-27-2006, 01:09 AM
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Cindy
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11-27-2006, 01:16 AM
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But since were on the subject lets also talk about DOMS or delayed onset muscle soreness which most people also assoicate with Lactate and or Lactic Acid. Whats your viewpoint on it.
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11-27-2006, 01:21 AM
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ok sorry im not done reallyy
sorry not quite finished with that talk though but uhm yeah i looked it up on sparknotes cuz i was still kinda unsure and...
"Anaerobic Respiration Aerobic respiration requires oxygen. However, some organisms live in places where oxygen is not always present. Similarly, under extreme exertion, muscle cells may run out of oxygen. Anaerobic respiration is a form of respiration that can function without oxygen. In the absence of oxygen, organisms continue to carry out glycolysis, since glycolysis does not use oxygen in its chemical process. But glycolysis does require NAD+. In aerobic respiration, the electron transport chain turns NADH back to NAD+ with the aid of oxygen, thereby averting any NAD+ shortage and allowing glycolysis to take place. In anaerobic respiration, cells must find another way to turn NADH back to NAD+. This “other way” is called fermentation. Fermentation’s goal is not to produce additional energy, but merely to replenish NAD+ supplies so that glycolysis can continue churning out its slow but steady stream of ATP. Because pyruvates are not needed in anaerobic respiration, fermentation uses them to help regenerate NAD+. While employing the pyruvates in this way does allow glycolysis to continue, it also results in the loss of the considerable energy contained in the pyruvate sugars. There are two principle forms of fermentation, lactic acid fermentation and alcoholic fermentation. For the SAT II Biology, remember that no matter what kind of fermentation occurs, anaerobic respiration only produces 2 net ATP in glycolysis. Lactic Acid Fermentation In lactic acid fermentation, pyruvate is converted to a three-carbon compound called lactic acid: pyruvate + NADHlactic acid + NAD+ In this reaction, the hydrogen from the NADH molecule is transferred to the pyruvate molecule. Lactic acid fermentation is common in fungi and bacteria. Lactic acid fermentation also takes place in human muscle cells when strenuous exercise causes temporary oxygen shortages. Since lactic acid is a toxic substance, its buildup in the muscles produces fatigue and soreness. im not trying to argue with you reallyy. i totally respect your view on it , but im just sharing what i know from the classes i took.
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11-27-2006, 01:24 AM
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do me a favor and post your references I wanna look into this. If i'm correct this is kind of old research and their has been some new cutting edge research lately, I'll look for it and post you a link.
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11-27-2006, 01:31 AM
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here's the site, just scroll down to anaeorobic http://www.sparknotes.com/testprep/b...section1.rhtml
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11-27-2006, 01:34 AM
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11-27-2006, 01:36 AM
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It seems that research was just put on sparknotes. I doubt they came up with their own SAT study guide...
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11-27-2006, 01:36 AM
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lollercopter
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11-27-2006, 01:37 AM
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Before you say someone is wrong, please try to do more academic research (i.e. pubmed)
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Cindy
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