Bookmark Website  | Free Registration  | The Team
The Lounge  | Champions  | The Wire |  Schedule |  Audio  |  Arcade  |  The Top Ten  |  Historical  |  Email  |  Video

The Truth About Lactate and Exercise


For years exercise scientists and physiologists have preached that lactate/lactic acid build-up in the muscle is the direct cause of muscle fatigue and a decrease in performance. It is proposed that lactate builds up in the muscle cells during intense exercise and literally "poisons" them, essentially shutting down activity biochemically by reducing the pH or increasing the acidity level. Lactate has therefore been dubbed a metabolic by-product or dead end and as the enemy of human exercise and performance. This may be far from the truth as this article explains.

Unfortunately, the information that gave lactate this unearned reputation is outdated and very questionable since the research on which this theory is based was isolated frog muscle experiments from 1910-1914. The experiments were performed and the lactate theory proposed by A.V. Hill and associates. Basically, these investigators took excised frog muscle and continuously stimulated it with electric shocks until failure and then took lactate samples for analysis. Lactate levels were extraordinarily high, and from this finding the scientists came to the conclusion that lactate buildup must have been the culprit for the fatigue and ultimate failure of the muscle. Hill also concluded that since there was no blood and therefore oxygen supply to the muscle, that this condition must have been the cause of the accumulation of lactate.

These investigations however were highly flawed in their design, since the muscle had been removed from both its nervous and its circulatory (arteries and veins) systems. Since the electrical stimulus was applied at a fixed voltage from an external source, one cannot correlate this with the situation of a live muscle in an animal with a nervous system and brain that regulates nervous and motor input to the muscles. One must account for the possibility of central or nervous fatigue limiting activity. With the absence of a circulatory system, how was the generated lactate supposed to be transported away from the working muscle via the veins? Also, the regulation of metabolism, which is highly dependent on hormonal control, was eliminated with the loss of blood circulation. Clearly, there were big problems with these early experiments, but amazingly the theory in all its weakness has been upheld to the present day!

Few people realize that lactate generation is actually necessary to allow moderate to intense exercise to occur. It is the conversion of a product known as pyruvate to lactate that enables the glycolytic (a fast energy generating metabolic process using glucose) system to continue working at a fast rate. Lactate is formed during moderate to intense exercise, when the human body relies heavily on carbohydrates and the glycolytic system to produce energy. All metabolic processes are highly regulated and only a fixed amount of energy-supplying product or substrate may be used at a time before a backup or "metabolic bottleneck" develops. A good analogy to visualize the regulation of a metabolic pathway is to consider energy substrates as an army of soldiers marching to, and through a tunnel. When the first few soldiers enter, they can move quickly and unrestricted, but as the number trying to enter increases, the process slows down dramatically. The conversion of pyruvate to lactate prevents the excess pyruvate from clogging up the pathway, bringing glycolysis to a grinding halt. This slowing of glycolysis obviously does not occur, because if it did running events such as the 400m would be impossible. As we shall see in another article on this site, the accumulation of lactate in the blood is the direct result of this "redirection" of energy in the body not because of a lack of oxygen in the muscles as Hill proposed. (see The Lactate Threshold - Reality or Fallacy? ). Lactate as will be described below, is actually a useful and readily available source of energy for the body to utilize.

Recent research is supplying some very interesting information concerning the role of lactate and muscle performance. George Brooks at the University of California at Berkeley has dedicated much of his career to exploring the role of lactate during exercise. Brook's investigations indicate the presence of a "lactate shuttle" that allows for the transportation of lactate from one muscle to another. The glycogen (stored carbohydrate) stored in muscle is destined for use in this tissue only, unlike liver tissue, which is able to release glucose into the bloodstream to be used by the rest of the body. The lactate shuttle is proposed as being a means for muscles to be able to "share" and redistribute their glycogen stores to other muscles and tissues in the form of lactate not glucose. For many years it was thought that lactate was a metabolic by-product that to be of any use it had to be transported via the blood to the liver to generate glucose via a process known as the Cori Cycle, but there is evidence to indicate that tissue such as red muscle, heart and brain tissue can directly oxidize the product. Therefore lactate can be utilized by tissue very close to, or even far from the source of generation. The shuttle works via the interaction of the circulatory system and the presence and operation of special transporter proteins located in muscle called mono carboxylic acid transporters (MCTs). These transporters are able to efficiently transport lactate from the blood into adjacent or distant muscles in the body. The inactive muscle can actually store the lactate, thereby further lowering the concentrations in the blood and active muscle. According to Brooks, lactate is far from a metabolic dead-end and may in fact be the most important metabolic fuel used by muscles especially during exercise. Estimates are that approximately 70% or more of the lactate generated during exercise is actually consumed or oxidized while only 19% is converted to glycogen.

In conclusion, the dubbing of lactate as a metabolic dead-end and as an exclusive cause of muscle fatigue was hasty but may have seemed appropriate at the time. Since then however technological advances in research have provided some quite contradictory evidence to the role of lactate. Amazingly, lactate may in fact be a "super fuel" for the body during exercise sessions that produce large quantities of the product. Exercise science will continue to investigate the role and contribution of lactate to exercise but in the meanwhile runners and athletes alike can rest assured that lactate is not the enemy but may in fact be an ally.

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:

Tech Times

Pre-breakfast Exercise More Effective for Weight Loss, Helps Burn More Fat: Study
Tech Times
The study involved healthy young men who were divided in three different groups with different exercise routines. All the participants were asked to consume a diet that comprised about 30 percent additional calories and around 50 percent extra fat than ...
Pre-breakfast exercise helps with weight loss and insulin resistance, study findsSydney Morning Herald

all 6 news articles »


The Guardian

Exercise is not a lifestyle statement so why spend a fortune on sportswear?
The Guardian
The theory behind expensive exercise clothes is that if you know you look good in them, you'll exercise more. But speaking as someone who is lucky enough to be able to exercise occasionally, I can tell you that this is gold-plated nonsense. People ...



How One Woman Overcame Her Exercise Addiction
Shape Magazine
I can trace the roots of my exercise addiction back to the first time I snuck off to my room to do jumping jacks, lunges, burpees—anything that would up my heart rate and help me take control of my body. It started after my parents sent me, at 13, to ...



Washington Times

Virginia Senate OKs bills on exercise, discipline in school
Washington Times
The Virginia state Senate easily passed bills Tuesday that would require students in kindergarten through fifth grade to exercise an average of at least 20 minutes per day and direct the state Board of Education to develop regulations on the use of ...

and more »


NBCNews.com

10 Die in F-16 Fighter Jet Crash During NATO Exercise in Spain
NBCNews.com
A Greek F-6 fighter jet crashed during a NATO exercise in Spain on Monday, killing 10 people and wounding at least 21, including as many as six American service members who suffered minor injuries. The crash happened shortly after takeoff from Los ...
Greek F-16 crashes in Spain during NATO exercise, killing 11CNN International
Greek jet crashes in NATO training exercise, 10 dieWHNS Greenville
F16 crashes after 'losing power during training exercise' killing 10 peopleExpress.co.uk

all 748 news articles »


The power of exercise for Parkinson's disease
myfox8.com
HIGH POINT, N.C. — Research has shown that increased intensity, duration and frequency of activity/exercise can significantly improve function and mobility for Parkinson's disease patients. Specifically, high intensity, progressive aerobic activity ...
Two studies shows exercise improves symptoms of Parkinsons and also helps ...Next Big Future

all 2 news articles »


JOE

Correcting 4 common exercise myths
Richmond County Daily Journal
We are bombarded by misinformation about exercise and nutrition these days. Between infomercials offering quick fixes to websites that promise abs without effort, it's easy to see why so many people don't know what to believe when it comes to a proper ...
Easy exercise of the week: CrunchesJOE

all 2 news articles »


The Tennessean

First comes exercise, then comes love
The Tennessean
So the pair exercised together, and afterwards spent three hours outside the gym on a bench just talking. “It is history from there,” she says. When he proposed, he recruited her sisters and arranged to surprise her during one of their regular girls ...



Care2.com

Too much sitting may have some serious health effects — even if you exercise
Washington Post
People who sit too much every day are at an increased risk of diabetes, heart disease, cancer and shorter life spans, even if they exercise, a new study finds. “More than one-half of an average person's day is spent being sedentary — sitting, watching ...
Sitting can be deadly, even if you exercise regularlyAMERICAblog (blog)
No, Health Experts Didn't Just Say 20 Minutes of Exercise is 'Enough'Care2.com
Sitting will kill you, even if you exerciseKBZK Bozeman News
News24 Nigeria
all 20 news articles »


Huffington Post

Overrated Exercises, And The Moves You Should Do Instead
Huffington Post
No doubt, any exercise is better than no exercise at all. Click Here to see the Complete List of Overrated Exercises, And The Moves You Should Do Instead. So, while it's silly to say that an exercise is "useless," it's not unfair to say that some ...


Google News


Advertisement



Section Site Map - Submit News - Feedback - Comments - Advertise with Us

Copyright 2006 Luminati Inc. All rights reserved.