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.
Exercise And Stress
"Stress is when you wake up screaming and you realize you haven't fallen asleep yet."Kim rolled over and reached for alarm that rang much too early.
The Truth about Spot Reduction
At any point, we can pick up the latest fitness magazine or see a television ad for the newest "abdominal reducer" exercise. These gimmicks are feeding on society's obsession with a "six pack" and everyone is searching for the answer to lose those love handles.
Lance Armstrong and Exercise - From Denial to Desire!
Press Conference 1996 - Lance ArmstrongOn Wednesday October 2, I was diagnosed with testicular cancer. I have been made aware that it has spread to other parts of my body.
Metabolism: How to Increase Your Metabolic Rate?
Metabolism is a process by which the body burns the calories and convert them into useful energy. High metabolic rate uses up the energy stored in the form of fat.
Got A Cold - Should You Work Out?
A recent study sponsored by the American College of Sports Medicine indicates that exercising moderately while you have a common cold doesn't affect the severity or duration of the symptoms.It's a widely excepted notion that exercising and keeping in shape will reduce your risk of getting sick, but nothing has been previously documented to demonstrate whether working out while suffering from a cold would reduce or intensify the symptoms.
The Two Greatest Myths About Abdominal Exercises
If you have ever read a fitness magazine..
Stretching for Health
Lack of flexibility is now seen to be a major cause of general health problems and sports injury and is being linked to everything from stress. back pain, and even osteoarthritis.
People Walking: How Some People Enjoy Their Exercise Walking
People walking regularly for exercise often walk for more than just that. They are those who have found their sweet spot in walking.
The History of Pilates - It All Began With One Sickly Child
A look into the history of Pilates helps you understand the tremendous power that this form of exercise has to help strengthen and transform your body. Unlike yoga, which has a tradition that goes back thousands of years, one individual developed the Pilates Method at the beginning of the twentieth century.
Monitor Your Body Fat Levels For Results
A very important aspect in really finding out if you're on the right track or not, is to monitor your body fat levels. Go to your local sports store and buy some body fat calipers to test your fat levels.
See How Trampolines Can Be Part Of Any Exercise Program
When the trampoline was invented by a young boy intriguedby the ability of aerialists to bounce in a net and performartistic maneuvers while they did so, it literally becamethe "springboard" for a whole new sport.George Nissen, who was a tumbler and gymnast himself, tookthe sports to a whole new height by putting them on canvasstrung in a metal frame.
Thirty Minutes of Exercise a Day Keeps the Doctor Away
"Exercise is good for you!" If you had a dollar for every time you heard this statement uttered, you'd be rich by now, right? Well, proponents of everyday physical activity aren't just blowing smoke when they repeat this mantra. Medical research has uncovered resounding evidence to back up this "good for you" claim.
Invest in Your Health
What if a trusted friend were to tell you about an investment where you could not possibly go wrong..
5 Mistakes People Makes When Doing a Workout Program
When you start out with a workout program - whether the purpose is weight loss exercise or another - you have started a training process that hopefully is going to last for a while. It is important that you are aware of some factors that can decrease your motivation for the exercising or even damage your health - while you are executing your training program.
Debunking Common Exercise Myths, Part 1
Myth #1: Heavy weights make you "bulky"Heavy weights typically do not lead to increased muscle mass, moderate weights do. Muscle mass is more of a function of volume (ie.
After WLS: Walking for Wellness
Step for step, mile for mile, walking is the best cardiovascular activity you can include as part of your weight loss surgery success story. Walking is easy, accessible, inexpensive, individual and effective.
How to Avoid Using Your Home Gym as a Clothes Rack
So here's the situation?You have a home gym, treadmill, elliptical trainer, or some other piece of home fitness equipment. But it's sitting in the corner of the room being used as a clothes rack.
Recognize Your Motivation to Exercise
The positive effects of exercise have been documented and reported through every media outlet available. You can probably walk up to anyone on the street and ask them the positive benefits of exercise and they can most likely list them.
Why Do My Feet Hurt So Much When I Run?
If you are a seasoned runner you know the importance of a good running shoe. It can make the difference between a great running experience and potential injury.
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.