| |
| |
|
Exercise Information |
|
|
|
The Lactate Threshold - Reality or Fallacy?
For many years exercise science has perpetuated the concept of a lactate threshold - a point during exercise where a sudden, sharp increase is noted in the concentration of lactate in the blood. This phenomenon is supposedly noticed when blood samples are taken from subjects performing incremental to max exercise tests much the same as a VO2 max test. Traditionally, it has been noted that when concentration of lactate is plotted against running speed (or %VO2 max) on a graph, as the individual runs faster the quantity of lactate in the blood remains constant up to a certain speed, after which a sudden inflection in the gradient occurs. This inflection point has been dubbed the lactate threshold - the point during intense exercise where the muscles become increasingly anaerobic, generating vast quantities of lactate. Therefore, this phenomenon has also become known as the anaerobic or ventilation threshold. As discussed in an earlier article on lactate featured on this website, early exercise scientists (and even some present day ones) attributed the increasing amounts of lactate in the blood during exercise to a lack of oxygen supplied to the muscles. This theory holds that the cardiorespiratory system must be inefficient at matching blood (oxygen) supply to the muscles and exercise intensity. Therefore, as the intensity of exercise increases, the muscles have to rely increasingly on "oxygen independent" (anaerobic) metabolism and its associated lactate generation. What these researchers failed to understand, or were unaware of was that as the intensity level (power output) of exercise progressively increases, there is a corresponding increase in the dependence of the glycolytic energy system. It is now universally accepted that energy systems are exercise intensity dependent. As explained in the previous article on lactate, this accumulation of lactate is a necessary consequence to maintain the increased flow of energy through the glycolytic pathway. Tim Noakes at the University of Cape Town, South Africa states that it is highly unlikely that the muscles ever become truly anaerobic. He provides some powerful evidence to back up this statement and quite possibly the most convincing might be what he calls the "lactate paradox". In his studies of the results of several research papers on Everest climbing expedition experiments, Noakes noted that lactate accumulation in the blood actually decreased as attitude increased. This finding is the exact opposite of what one would traditionally expect since as altitude increases, the ambient barometric pressure decreases, as does the relative availability of oxygen in the inspired air. Therefore, one would suspect that near the peak of Everest, the exercising muscles must be truly anaerobic and generating large amounts of lactate but as mentioned previously, this does not occur. Professor Noakes explains that at such an extreme altitude, some internally regulated factor (possibly the brain) severely limits the intensity of exercise to protect the heart therefore also limiting the amount of lactate production. Additional research, has demonstrated that even at rest under more than adequate oxygen availability, muscles generate lactate. Furthermore, other researchers have failed to find conclusive evidence that muscles become anaerobic at exercise intensities approaching the lactate threshold or even during maximal exercise. Therefore, Noakes prefers to refer to anaerobic metabolism as "oxygen independent" metabolism since in his astute opinion there exists no such thing as anaerobic muscle. Noakes dismisses the probability of a sudden increase in lactate concentration. He explains that if too few blood samples are taken - say for every three or four kilometers per hour increase, then when the rise in lactate is actually observed, it may indeed show a precipitous "jump" from the one observation to the next. If samples are taken more frequently however, say at every speed increment, then the increase is much more gradual, producing a smoother logarithmic or hyperbolic curve. Dr. Noakes indicates that lactate buildup during increasingly intense exercise is the result of its production rate exceeding its clearance. As mentioned in our article,Lactate is NOT the Culprit!, Brook's lactate shuttle is purported as being responsible for assisting with the transport, utilization and clearance of lactate during exercise. At lower exercise intensity levels, the rate of lactate clearance is able to match the rate of production. However, as exercise becomes increasingly more intense and more muscle mass is recruited, proportionately large quantities of lactate are produced, but it is unlikely that clearance via the shuttle will be able to maintain pace. Therefore, there exists a speed or intensity level at which the production of lactate surpasses its clearance and the blood concentration begins to steadily increase. This point is what Noakes prefers to call for lack of a better word - the "lactate turnpoint" and that it occurs at an intensity/speed where the concentration of lactate in the blood is approximately 3.0 mmol/L. If the individual were to run at this constant speed, this would be called running at the subjects "lactate steady state". In theory this is the fastest speed that can be maintained by the exerciser for extended periods of time such as marathon running. Therefore, from discussions in this and previous articles, it is safe to conclude that lactate production in the body is the direct result of an increased reliance on the glycolytic energy systems, not from a lack of oxygen in the muscles. Paired with this increased use of oxygen independent metabolism is an increase in lactate production. The sudden jump in lactate production simply does not exist; it increases proportionally with the increased exercise intensity or power output. In addition, it should be obvious that the term anaerobic threshold is a misnomer and that perhaps the only appropriate term to refer to this phenomenon is the lactate turnpoint. References and further reading: more information on the concept oxygen independent metabolism and the lactate turnpoint may be found in Lore of Running - a classic book in its fourth edition dedicated not only to running performance, but to cutting edge exercise physiology as well. David Petersen is a Personal Trainer/Certified Strength and Conditioning Specialist and the owner and founder of B.O.S.S. Fitness Inc. based in Oldsmar, Florida. More articles and information can be found at http://www.bossfitness.com NOTE: You're free to republish this article on your website, in your newsletter, in your e-book or in other publications provided the article is reproduced in its entirety, including this note, author information and all LIVE website links as above.
MORE RESOURCES:
Exercise - Google News |
|
|
|
RELATED ARTICLES
Bodybuilding and Exercise - The Ten Commandments in Making of a Champion! 1. Fill your life up with different hobbies! - Bodybuilding Champions realize working out is not everything there is in life. 4 Exercises That Will Help You Change Your Body Faster Than Any Other Exercises You May Have Tried 1. Lunges with a barbell. Workout Without a Gym You may also have no access to a commercial gym, home gym or are on business trip, but there can be a solution, a strength-training workout without the need of expensive machines.As with any exercise, whether you are using your own body weight, machines or free weights, if the resistance doesn't increase, your muscles won't be worked to their maximum capacity and the stimulus these fibres need to grow will be missing. How to Get The Most From Your Home Workouts A recent study found that home workouts may do even more good than workouts at a gym. This is good news for people who are time crunched and find it's too much trouble to make it to a health club. Thick Today Is Fat Tomorrow As we twentysomethings get further along in our twenties, we may start to notice ourselves gaining weight. It sucks, because at one time you could eat whatever you wanted and now it's like someone shut off your metabolism. Working Out - Its Good For You When we think about the life in the country, there is always something rosy about it. What is it that the people in the country have that we do not? When you ponder about it you find that those lucky souls eat good food, they work really hard, by work I mean real physical work and they have good night's sleep. Movement That Matters: Exercise With a Greater Purpose You've seen the commercials Ive fallen and I cant get up! While this has been a topic of many jokes and late-night comedy skits, the reality is falling is a very real danger for many people. Too often falls can lead to broken bones, hospitalization, and sometimes life-threatening illnesses due to being confined to a bed while recovering. Take a Break Writing is a strenuous creative activity, and like physical activity it produces fatigue that requires rejuvenation and renewal, so when the mind is blocked, it is time to rest it. Many writers call this 'writer's block' but others claim that no such state exists. How to Get Better Exercise Results By Improving Hydration Water and ExerciseYour body excretes water in a number of ways: through urination, defecation, breathing (that's why we always enjoyed breathing condensation on mirrors when we were kids) and perspiration. And when you are exercising, your body can lose a large amount of water. The Right Exercise Intensity We've all heard the exercise guidelines that recommend we participate in 30 minutes of moderate intensity physical activity 3-5 times per week. That seems easy enough to implement. How To Gain An Avalanche Of Energy! For many people out there trying to become more energised and active they are terrified of committing to daily activity. It is so engrained in their minds that they might over train that they literally shy away from daily physical training and instead follow the herd and train two or three times per week. 3 Great Weight Loss Exercises It's a given that effective weight loss is much more then simply going on a "diet". To really lose weight and (hopefully) keep that weight off, you need to add exercise to the equation. Top 10 Tips For Finding Time For Exercise If you're like most people, finding time for exercise is difficult. Here are my "top 10" tips to help you in that quest. A Great Way To Spice Up Your Workouts -- Interval Training There's been a lot of buzz recently about Interval Training. So, you may be wondering what it really is and, more importantly, why you should incorporate it in your fitness workouts. The Importance Of An Active Lifestyle Over the past 15 years or so, we have been told that a healthy lifestyle is important. Scientists recommend we should be accumulating on average 60 minutes of exercises a day in order to maintain healthy levels. Incorporating Physical Activity into Your Daily Routine Not as Hard as You Think You already know that getting at least 30 minutes of exercise each and every day is good for you, but putting that assertion into actual practice is an entirely different matter, right? Contrary to what you might think, making physical activity an everyday habit isn't rocket science. There's no secret code for success waiting to be cracked. 10 Best Workout Tips Top Trainers share their secrets to getting slim, toned and strong in record time. It guarantees that you will see results in no time. The Top 10 Reasons Why Your Dog is a Great Workout Partner 1) He or she is never late for a workout session. Chances are good that your dog lives with you and has a reasonable clear schedule. When Exercising Right Looks Wrong II Enter any health club and a concept is very apparent, the same exercise performed again and again. Crowded floor space taken up by machines designed to make exercise easier, and a thought process called 'gym science' which involves no science at all. Your Guide To Exercise Even light exercise is good for you, so don't get discouraged!The most important thing to remember about exercise is that you should pick something you enjoy doing first, and then worry about whether or not it's the best exercise for you later.The biggest mistake that most people make when they start an exercise routine is the choice of exercise.
|
| home | site map |
| © 2006 |
