VO2max

The monthly newsletter of RunCoachJason.com

Jason Karp, professional coach, consultant, freelance writer

April, 2006

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In this issue:

Altitude

The Genetics of VO2max

Lactate—Fatigue’s Faulty Scapegoat

Athlete Spotlight

Research

In Press

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Altitude

Now that I have moved to Albuquerque, New Mexico, I find myself thinking a lot about altitude...

(excerpted from Karp, J.R. and Kelley, L.C. Running at Altitude. Track Coach. 160:5097-5100, Summer 2002.)

 

From the moment you step off the airplane at altitude, changes in the body can be detected.  Some of these changes include reductions in the oxygen content of the blood, blood plasma, total blood volume, stroke volume, and cardiac output, and increases in ventilation, fluid loss, resting heart rate, and basal metabolic rate.  These changes result from the decreased barometric pressure occurring at altitude, and are exacerbated during exercise, when there is a greater demand for oxygen.  The most noticeable of these changes is the increased ventilation, which decreases the partial pressure of carbon dioxide in the blood, elevating the pH.  In response to this respiratory alkalosis, the kidneys compensate by excreting bicarbonate (called renal compensation) to lower blood pH back to its normal physiological value.  Since the fraction of oxygen in the air is constant regardless of the altitude, an increase in altitude and the accompanied decrease in barometric pressure will decrease the amount of oxygen in the air.  In addition, altitude decreases the partial pressure of oxygen in the lungs, thus decreasing the pressure gradient between the lungs and the blood.  Since molecules travel from areas of higher pressure to areas of lower pressure, the smaller pressure gradient decreases the amount of oxygen entering the blood.  The obvious implication for athletic performance is less oxygen being available to the heart and the skeletal muscles, thus decreasing the ability to work at a high aerobic intensity.

 

When competing at altitude, two issues need to be considered.  The first is minimizing the chances of experiencing symptoms of acute mountain sickness, and the second is how much time the body needs to acclimatize to the less available oxygen.  Unless you are able to train at altitude for at least two weeks before your race, you should arrive as close as possible to the race.  The physiological changes that occur at altitude seem to exhibit the greatest detrimental effect on performance between 10 and 14 days of exposure.  Over the following few weeks the body acclimatizes, such that the consequence of those changes are less severe.  For example, the formation of new red blood cells to carry oxygen has been detected after one week of altitude exposure.  However, acclimatization does not completely counteract the fundamental stress of altitude, and changes in the cardiovascular system do not return to what is characteristic at sea level.  Although arriving only a couple of days before the meet does not allow enough time for the body to fully acclimatize, and increases the chances of acquiring acute mountain sickness, competing soon after arrival may not hurt your performance as much as arriving a week before.  Within the first 48 hours after arrival at altitude, performance may still be close to that attained at sea level. 

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The Genetics of VO2max

While most runners would like to believe that they can control their destiny through training, VO2max and endurance performance have genetic limitations.  A number of studies have shown that VO2max has a strong genetic component to it.  One of these studies, published in Clinical Science in 1997, examined the relationship between VO2max and human leukocyte antigen (HLA, a group of genes on human chromosome 6) in 16 pairs of twins (8 identical, 8 fraternal).  The researchers found a high correlation between the presence of two specific DNA codings of the HLA genes and VO2max.  The subjects that had the specific DNA codings had a significantly greater VO2max than those who did not have the specific DNA codings (71 vs. 58 ml/kg/min).  Interestingly, even in two pairs of fraternal twins, the higher VO2max value corresponded to the twin with the specific DNA coding. 

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Lactate as Fatigue’s Faulty Scapegoat: Should We (Scientists) Take the Blame?

From the time A.V. Hill and Otto Meyerhof discovered in the 1920s that lactic acid is produced during fatiguing muscle contractions in the absence of oxygen, lactic acid has been both the fitness professional’s and the general public’s scapegoat for fatigue.  Indeed, one does not have to get too deep into a conversation with a coach, a personal trainer, or a recreational jogger to discover that lactate is still viewed as the enemy.  But why does lactate get all the blame?  It has been long accepted by the scientific community that lactate is innocuous and is not the cause of fatigue during intense exercise.  Moreover, recent studies on single muscle fibers have shown that lactic acid can restore force production in skeletal muscle when in a fatigued state. 

Significant correlations have been reported between lactate concentration, pH, and fatigue.  While a correlation does not imply cause and effect, the present-day dogma held by those outside the scientific community is likely a result of the misinterpretation of this research as well as the wealth of implicit and explicit associations made between lactate and fatigue.  Given the innumerable daily laboratory observations that lactate accumulation and fatigue happen concurrently, it is easy to see how a cause-and-effect relationship can be assumed.  However, there has never been any experimental evidence that has shown a cause-and-effect relationship between muscle or blood lactate concentration and fatigue. 

 

Scientific terminology concerning lactate has also undoubtedly contributed to the continued blame of lactate for fatigue.  Terms like lactate threshold, lactic acidosis, onset of blood lactate accumulation, and maximal lactate steady state are misleading because they place the emphasis on lactate and proliferate the stereotype that lactate is the “bad guy” that needs to be dealt with or avoided.  Although terms that contain the word lactate are technically correct from a measurement definition, they lack a more useful conceptual or operational definition.  Since it is the acidosis and its ramifications that we are most interested in, rather than the lactate molecule, it may be more appropriate to refer to the lactate threshold as the acidosis threshold. 

 

Because of lactate’s concomitant increase with other products of metabolism that have been implicated in fatigue (e.g., hydrogen ions, potassium ions, and inorganic phosphate) and the simple method of measuring its concentration in the blood, lactate is used only as an indirect measure of acidosis.  However, its portrayal in the scientific literature is not only as a measure of the physiological challenge of exercise but also as having a close association with acidosis and fatigue.  While some recent editions of textbooks in exercise physiology and biochemistry have done an adequate job elucidating the relationship of lactate to acidosis and fatigue, the handling of this subject in others is still wanting.

 

Despite our knowledge of lactate and fatigue, scientific terminology is, unfortunately, slow to change, and inaccurate conclusions made by those outside the scientific community have been the chief result. 

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Athlete Spotlight

Jonathan Rossing

 

A doctoral student in rhetoric, Jonathan began working with Coach Jason in January to improve his marathon performance.  Focusing on the shorter distances before returning to the marathon this summer, he recently placed 2nd at the Last Chance for Boston Marathon 5K in Columbus, OH (17:25) and 3rd at the Heart Marathon 5K in Cincinnati, OH (17:15). 

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Research

I recently presented my research, Training Characteristics of U.S. Olympic Marathon Trials Qualifiers, at the 8th annual conference of the American Society of Exercise Physiologists in Albuquerque , NM .

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In Press...

Turn on the Power: Energy System Specific Training, my article on how to get the most out of your training by targeting the 3 energy systems used to run, appears in the May, 2006 issue of Running Times, on newsstands in April.

 

My Fitness News contributions on cardio-weight training order, post- workout nutrition, reducing inflammation after workouts, and staying cool during exercise appears in the May, 2006 issue of Oxygen magazine, on newsstands in April.

 

Your Ultimate Fat-Burning Cardio Program, my article on the top 3 fitness-inducing, fat-burning cardio workouts, appears in the April, 2006 issue of Oxygen magazine.

 

The Burning Question, my article that details five ways to tweak your training to burn more calories, appears in the April, 2006 issue of Runner’s World.

 

Workout Express, my column that details a 30-minute cardio workout, an accompanying playlist of songs, and a single “must-do” strength exercise, appears in the April, 2006 issue of Shape magazine.

 

I’m also quoted in Bob Cooper’s article on changing the training stimulus in the May issue of Runner’s World, on newsstands in April.

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©2006 Jason Karp.  All rights reserved.