Guest guest Posted May 16, 2006 Report Share Posted May 16, 2006 Today's New York Times, in the Health section had an article on this subject. Extracts below: Lactic Acid Is Not Muscles' Foe, It's Fuel http://www.nytimes.com/2006/05/16/health/nutrition/16run.html Everyone who has even thought about exercising has heard the warnings about lactic acid. It builds up in your muscles. It is what makes your muscles burn. Its buildup is what makes your muscles tire and give out. Coaches and personal trainers tell athletes and exercisers that they have to learn to work out at just below their " lactic threshold, " that point of diminishing returns when lactic acid starts to accumulate. Some athletes even have blood tests to find their personal lactic thresholds. But that, it turns out, is all wrong. Lactic acid is actually a fuel, not a caustic waste product. Muscles make it deliberately, producing it from glucose, and they burn it to obtain energy. The reason trained athletes can perform so hard and so long is because their intense training causes their muscles to adapt so they more readily and efficiently absorb lactic acid. The notion that lactic acid was bad took hold more than a century ago, said A. , a professor in the department of integrative biology at the University of California, Berkeley. It stuck because it seemed to make so much sense. " It's one of the classic mistakes in the history of science, " Dr. said. Its origins lie in a study by a Nobel laureate, Otto Meyerhof, who in the early years of the 20th century cut a frog in half and put its bottom half in a jar. The frog's muscles had no circulation — no source of oxygen or energy. Dr. Myerhoff gave the frog's leg electric shocks to make the muscles contract, but after a few twitches, the muscles stopped moving. Then, when Dr. Myerhoff examined the muscles, he discovered that they were bathed in lactic acid. A theory was born. Lack of oxygen to muscles leads to lactic acid, leads to fatigue. Athletes were told that they should spend most of their effort exercising aerobically, using glucose as a fuel. If they tried to spend too much time exercising harder, in the anaerobic zone, they were told, they would pay a price, that lactic acid would accumulate in the muscles, forcing them to stop. Few scientists questioned this view, Dr. said. But, he said, he became interested in it in the 1960's, when he was running track at Queens College and his coach told him that his performance was limited by a buildup of lactic acid. When he graduated and began working on a Ph.D. in exercise physiology, he decided to study the lactic acid hypothesis for his dissertation. " I gave rats radioactive lactic acid, and I found that they burned it faster than anything else I could give them, " Dr. said. It looked as if lactic acid was there for a reason. It was a source of energy. Dr. said he published the finding in the late 70's. Other researchers challenged him at meetings and in print. " I had huge fights, I had terrible trouble getting my grants funded, I had my papers rejected, " Dr. recalled. But he soldiered on, conducting more elaborate studies with rats and, years later, moving on to humans. Every time, with every study, his results were consistent with his radical idea. Eventually, other researchers confirmed the work. And gradually, the thinking among exercise physiologists began to change. " The evidence has continued to mount, " said L. Bruce Gladden, a professor of health and human performance at Auburn University. " It became clear that it is not so simple as to say, Lactic acid is a bad thing and it causes fatigue. " As for the idea that lactic acid causes muscle soreness, Dr. Gladden said, that never made sense. " Lactic acid will be gone from your muscles within an hour of exercise, " he said. " You get sore one to three days later. The time frame is not consistent, and the mechanisms have not been found. " ------------- Carson Wood Westbrook, ME USA. > Dr. Peck, > > I think Mr. Mendoza could be referring to a review article published > in AJP by Robergs and colleagues: > > http://ajpregu.physiology.org/cgi/content/short/287/3/R502 > > In short, they propose that lactate is not the culprit in human > muscle fatigue, but may aid in muscle activity. To add to the > discussion, here is a current debate published in the April 2006 > issue of JAP: > > Point:Counterpoint: Lactic acid accumulation is an > advantage/disadvantage during muscle activity > J Appl Physiol, Apr 2006; 100: 1410 - 1412. > > I have a PDF copy if you's like. Just e-mail me. > > Roy Coronado SPT, CSCS > Lubbock, TX Quote Link to comment Share on other sites More sharing options...
Guest guest Posted May 17, 2006 Report Share Posted May 17, 2006 There are two concepts being discussed here. 1) That lactate may not be the culprit in human muscle fatigue, but may aid in muscle activity. This is certainly an interesting area of study and a plausible theory. 2) Aside from the above, a statement was made that it is a " myth " that elevated lactate levels can cause an acidosis. This is what I take exception to. Serum lactate levels above 4-5 mEq/L are associated with lactic acidosis. This is well demonstrated in the laboratory as well as in clinical practice. Evan R. Peck, M.D. Baylor College of Medicine Houston, Texas, USA Quote Link to comment Share on other sites More sharing options...
Guest guest Posted May 18, 2006 Report Share Posted May 18, 2006 Hi In response to your question regarding latic acid, as you have already mentioned lactic acid or (lactate its salt) gets transported to the liver and used for energy (ATP resynthesis) via the cori cycle. However, your point about coaches telling athletes to train below the lactate threshold is not entirely correct, maybe this is true in village sports. However, this is not the case in elite sport. Endurance runners frequently train on the lactate threshold but not above it as once you hit the lactate threshold (once your blood lactate levels hit approx 4mmol/L then the lactate levels rise exponentially causing a cessation in performance. Now by training at the lactate threshold the body has to adapt to the slight increases in lactate levels and therefore can prolong endurance performance. This type of training is a better method for testing endurance runners aswell, compared to Vo2 max testing! Hope this helps and gives you a balanced view of the lactate threshold debate. Gareth s Wales UK > Today's New York Times, in the Health section had an article on this > subject. > > Extracts below: > > Lactic Acid Is Not Muscles' Foe, It's Fuel > > http://www.nytimes.com/2006/05/16/health/nutrition/16run.html > > Everyone who has even thought about exercising has heard the warnings about lactic acid. It builds up in your muscles. It is what makes your muscles burn. Its buildup is what makes your muscles tire and give out. > > Coaches and personal trainers tell athletes and exercisers that they have to learn to work out at just below their " lactic threshold, " that point of diminishing returns when lactic acid starts to accumulate. Some athletes even have blood tests to find their personal lactic thresholds. > > But that, it turns out, is all wrong. Lactic acid is actually a fuel, not a caustic waste product. Muscles make it deliberately, producing it from glucose, and they burn it to obtain energy. The reason trained athletes can perform so hard and so long is because their intense training causes their muscles to adapt so they more readily and efficiently absorb lactic acid. > > The notion that lactic acid was bad took hold more than a century ago, said A. , a professor in the department of integrative biology at the University of California, Berkeley. It stuck because it seemed to make so much sense. > > " It's one of the classic mistakes in the history of science, " Dr. said. > > Its origins lie in a study by a Nobel laureate, Otto Meyerhof, who in the early years of the 20th century cut a frog in half and put its bottom half in a jar. The frog's muscles had no circulation — no source of oxygen or energy. > > Dr. Myerhoff gave the frog's leg electric shocks to make the muscles contract, but after a few twitches, the muscles stopped moving. Then, when Dr. Myerhoff examined the muscles, he discovered that they were bathed in lactic acid. > > A theory was born. Lack of oxygen to muscles leads to lactic acid, leads to fatigue. > > Athletes were told that they should spend most of their effort exercising aerobically, using glucose as a fuel. If they tried to spend too much time exercising harder, in the anaerobic zone, they were told, they would pay a price, that lactic acid would accumulate in the muscles, forcing them to stop. > > Few scientists questioned this view, Dr. said. But, he said, he became interested in it in the 1960's, when he was running track at Queens College and his coach told him that his performance was limited by a buildup of lactic acid. > > When he graduated and began working on a Ph.D. in exercise physiology, he decided to study the lactic acid hypothesis for his dissertation. > > " I gave rats radioactive lactic acid, and I found that they burned it faster than anything else I could give them, " Dr. said. > > It looked as if lactic acid was there for a reason. It was a source of energy. > > Dr. said he published the finding in the late 70's. Other researchers challenged him at meetings and in print. > > " I had huge fights, I had terrible trouble getting my grants funded, I had my papers rejected, " Dr. recalled. But he soldiered on, conducting more elaborate studies with rats and, years later, moving on to humans. Every time, with every study, his results were consistent with his radical idea. > > Eventually, other researchers confirmed the work. And gradually, the thinking among exercise physiologists began to change. > > " The evidence has continued to mount, " said L. Bruce Gladden, a professor of health and human performance at Auburn University. " It became clear that it is not so simple as to say, Lactic acid is a bad thing and it causes fatigue. " > > As for the idea that lactic acid causes muscle soreness, Dr. Gladden said, that never made sense. > > " Lactic acid will be gone from your muscles within an hour of exercise, " he said. " You get sore one to three days later. The time frame is not consistent, and the mechanisms have not been found. " > > ------------- > > Carson Wood > Westbrook, ME USA. ------- > > Dr. Peck, > > > > I think Mr. Mendoza could be referring to a review article published > > in AJP by Robergs and colleagues: > > > > http://ajpregu.physiology.org/cgi/content/short/287/3/R502 > > > > In short, they propose that lactate is not the culprit in human > > muscle fatigue, but may aid in muscle activity. To add to the > > discussion, here is a current debate published in the April 2006 > > issue of JAP: > > > > Point:Counterpoint: Lactic acid accumulation is an > > advantage/disadvantage during muscle activity > > J Appl Physiol, Apr 2006; 100: 1410 - 1412. > > > > I have a PDF copy if you's like. Just e-mail me. > > > > Roy Coronado SPT, CSCS > > Lubbock, TX > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted May 18, 2006 Report Share Posted May 18, 2006 Gareth You said " once your blood lactate levels hit approx 4mmol/L then the lactate levels rise exponentially causing a cessation in performance. " I think Max's point is that lactate does not cause cessation in performance but is the bodies attempt to remedy the acidosis causing the drop in performance. High lactate levels at the point of exhaustion does not cause the failure but actually prolongs the muscles ability to perform. High serum lactate levels are a pointer to acidosis, are associated with acidosis and are closely correlated with acidosis (and other mechanisms of exhaustion) but are not its cause. If, as the paper to which he refers indicates, this is true does this affect lactate threshold training? Training at threshold does allow teach the body to learn to reprocess the lactate at higher level thus improving acidosis coping method. What else can we learn from the paper refer ed to. E.g. If learning to process lactate salts will help teach the body to improve coping mechanisms then will consuming these in the form of preparations drunk during training cycles improve the bodies lactate threshold? Or have training methods simply figured out what works and the science of physiology is only now catching up with explanations. Referring to the article Point:Counterpoint: Lactic acid accumulation is an advantage/disadvantage during muscle activity J Appl Physiol, Apr 2006; 100: 1410 - 1412. Regards Nick Tatalias Johannesburg South Africa Contact Conditioning Coach > > Hi > > In response to your question regarding latic acid, as you have > already mentioned lactic acid or (lactate its salt) gets transported > to the liver and used for energy (ATP resynthesis) via the cori > cycle. However, your point about coaches telling athletes to train > below the lactate threshold is not entirely correct, maybe this is > true in village sports. However, this is not the case in elite > sport. Endurance runners frequently train on the lactate threshold > but not above it as once you hit the lactate threshold (once your blood > lactate levels hit approx 4mmol/L then the lactate levels rise > exponentially causing a cessation in performance. Now by training at > the lactate threshold the body has to adapt to the slight increases > in lactate levels and therefore can prolong endurance performance. > This type of training is a better method for testing endurance > runners aswell, compared to Vo2 max testing! > > Hope this helps and gives you a balanced view of the lactate > threshold debate. > > Gareth s > Wales > UK > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted May 18, 2006 Report Share Posted May 18, 2006 The lactic acid system is capable of releasing energy to resynthesise ATP without the involvement of oxygen and is called anaerobic glycolysis. Glycolysis (breakdown of carbohydrates) results in the formation of pyruvic acid and hydrogens ions (H+). A build up of H+ will make the muscle cells acidic and interfere with their operation so carrier molecules, called nicotinamide adenine dinucleotide (NAD+), remove the H+. The NAD+ is reduced to NADH which deposit the H+ at the electron transport gate (ETC) in the mitrochondria to be combined with oxygen to form water (H2O). If there is insufficient oxygen then NADH cannot release the H+ and they build up in the cell. To prevent the rise in acidity pyruvic acid accepts H+ forming lactic acid which then dissociates into lactate and H+. Some of the lactate diffuses into the blood stream and takes some H+ with it as a way of reducing the H+ concentration in the muscle cell. 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). Damien Chiappini SPF Performance Pittsburgh Nick Tatalias wrote: <<<Gareth You said " once your blood lactate levels hit approx 4mmol/L then the lactate levels rise exponentially causing a cessation in performance. " I think Max's point is that lactate does not cause cessation in performance but is the bodies attempt to remedy the acidosis causing the drop in performance. High lactate levels at the point of exhaustion does not cause the failure but actually prolongs the muscles ability to perform. High serum lactate levels are a pointer to acidosis, are associated with acidosis and are closely correlated with acidosis (and other mechanisms of exhaustion) but are not its cause. If, as the paper to which he refers indicates, this is true does this affect lactate threshold training? Training at threshold does allow teach the body to learn to reprocess the lactate at higher level thus improving acidosis coping method. What else can we learn from the paper refer ed to. E.g. If learning to process lactate salts will help teach the body to improve coping mechanisms then will consuming these in the form of preparations drunk during training cycles improve the bodies lactate threshold? Or have training methods simply figured out what works and the science of physiology is only now catching up with explanations. Referring to the article Point:Counterpoint: Lactic acid accumulation is an advantage/disadvantage during muscle activity J Appl Physiol, Apr 2006; 100: 1410 - 1412.>>> Quote Link to comment Share on other sites More sharing options...
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